Environment, Ecology and Conservation – Basic ideas

by Mizanur Rahman Bhuiyan · February 17, 2014

The Environment

Environment means the combined influence of the Biotic and Abiotic factors around an organism that interact and influence the life and behaviour of it. Environment has a specific influence in the formation and functioning of life and none of the organisms are out of it. In fact, the surrounding Light, Air, Soil, Water, Temperature etc. have specific fluences on Plants, Animals and Micro-organisms in nature, all of which interact with each other to form the environment. So, life and environement are inseparable from each other, as food and shelter are the two important factors for survival, are supported by the latter. But, organisms are subjected to continuous interactive changes, as the environment changes constantly.

Environmental Biology

The branch of biology that deals with influence of organisms on their biotic and abiotic factors in nature and vice versa, is known as Environmental Biology. As the environment itself is formed by the organic and inorganic factors in nature, there has been a precise interaction among each and every factor, resulting in a sustainable adaptive continuous survival process. So, as the environment has an influence on the life style of organisms, similarly the latter has a similar influence on the former.

Ecology

The two Greek words Oikos (=habitat) and Logos (=knowledge), constitutes the word Ecology. It is the branch of biology that deals with the interaction of organisms with the enviroment and vice versa. A German scientist Earnest Heackel (1869) first coined the term and according to Eugene P. Odum (1963), Ecology is the structure and function of nature. So, the two terms Ecology and Enviromental Biology are not synnonymous, but bear different meanings.

Species

A Species is the basic unit (taxon, pl. taxa) and the lowest category of Classification. It is also the basic unit of organisms in nature for their Evolution and Reproduction. A group of very closely related (external and internal) organisms which produce viable and fertile offsprings among themselves and are reproductively isolated from similar other groups, is termed as a Species (pl. Species). John Ray (1686) first coined the term; and Henry Huxley (1859) said during his discussion on Charles Darwin’s – ‘The Origin of Species by means of Natural selection’, ” First of all what is a Species, is a very easy question, but much dufficult to answer, even for those who knows it very well’. In the same way, scientists have defined it from different point of view, like below –

Species are groups of closely related organisms which are capable of inter-breeding to produce fertile offspring.
Species are groups of inter-breeding natural population that are reproductively isolated from the other other such groups.- Earnst Mayr (1969); Mayr and Ashlock (1991).
A species is an evolved or evolving, genetically distinctive, reproductively isolated, natural population. – A. E. Emerson (1945)

But, whatever the case, the definition of Species is more clear than any other category (taxon) in the systematic hierarchy of classification. Each of the Species maintains its specific structural, behavioural and ecological characteristics distinct from any of its alikes, though they maintain some common ones to come under a Genus and in the same way in the higher categories. But, the similarities gradually decreases as we go higher in the category hierarchy and it increases when we compare the lower ones.

Since ancient times, it has been a practice crossing very closely related groups like a Horse and a Dunky, producing a Mule, for a better asthetic service; which is infertile, proving the parents fall under different Species. But, in the recent past, scientists have been crossing genetically close Species to find fertile offsprings. One of the best example is Liger, a cross result of a Lion and a Tigeress, which is infertile; but the opposite, i.e., a Tiger and a Lioness produced a Tiglon, which was fertile.

Characteristics for the identification of a Species

Though there is difference among the scientists in defining a Species, but they are unimental in identifying it; as all of them comply with a few characteristics which are used in identifying a Species, like –

A common descent – Each Species has a historical entity and is related to others for their origin from a common ancestor.
Smallest distinct organismal group – It must be a specific smallest unit in the pedigre (history of origin) on the morphological and chromosomal point of view.
Specific Intra-breeding group – Members of a given Species can only breed among themselves and are reproductively isolated from the members of other Species.
Specific ecological unit – Each Species maintains its own specific Ecological Niche (particular position in the eco-system) and is eco-ethologically isolated from any other Species inhabiting the same eco-system.
Specific genetical unit – Each Species maintains its own genetical collection and exchanges gene codes only among its members; they never exhange genes with the members of other Species.

Examples of Species – Paddy (Oryza sativa), Mango (Mangifera indica), Human (Homo sapiens), Toad (Duttaphrynus melanostictus)

Population

The word Population is derived from a Latin word ‘populus'(=people). In a general term, we understand the number of individuals of organisms in a given area. But, according to ecologists, a Population is defined as all the individuals belonging to a single Species occupying a local area of space. According to McNaughton (1973), a Population is a group of genetically similar individuals co-occuring in space and time. The total number of individuals in a given Population is known as its Population Size. For instance, the total number of Carps in a given pond, the total number of trees in a Rubber culture, the total number of Tigers (Panthera tigris bengalensis) and the total number of individuals inhabiting Dhaka City, can be an example of Population of those area.

Characteristics of Population

The characteristics of a Population are given below –

Population size and density – The total number of individuals (of different categories) of a given Population is termed as the Population Size. On the other hand, the number of individuals of a population in a given area is known as the Population Density; it is the number of individuals per unit area of a given population. For instance, the number of people per unit area like 1 sq. km. in Dhaka City; number of Earthworms in a given area per acre of land or the number of Zoo-planktons found per litre of water in a pond, are the best examples. But, population density in nature can be expressed in two ways, like –Dispersion – It is the distribution of the members of a given population on the basis of their inter-relationship. Dispersion of a population exhibits three patterns, like –
- Crude Density – When the density is expressed for the total number or biomass per unit area in a given time; e.g., The total number of candidates of Sylhet Govt. M.C. College of the year 2010.
- Ecological Density – When the density is expressed for the total number or biomass on the basis of a given habitat; e.g., The total number of candidates of Sylhet Govt. M.C, College of the year 2010 on the basis of the residential halls; i.e., the total number of cadidates per hall. Ecological density is also termed as, Specific Density.
Age Structure – Members of different populations are found of different ages. The relative resource or ratio of the members of each age group of a given population is termed as its Age Structure. The age distribution influences the natality and mortality of the members of a population to a greater extent. So, the ratio of the age group of a given population gives a precise idea about the current reproductive status as well as the fate of that population.
Birth rate or Natality – The total number of members of a given population added in a given unit of time is termed as its Natality or Potential Natality. This may be hampered due to natural calamities.
Death rate or Mortality – The total number of members of a given population died in a given unit of time is termed as its Mortality. Like the natality, the mortality can also be influenced by certain natural calamities like – Cyclone, Tidal bore, Surge, Innundation, Draught and over precipitation.

Factors of Population Change

Usually a population is sustained in a given eco-system; but fluctuations may occur in times due to certain factors. The population density or number of individuals per unit area, is expressed as Population Frequency, i.e., the number of samples occuring in that area. A few factors hamper this frequency in times, are given below –

The Natality (birth rate) rarely remains constant.
The Mortality (death rate) also vary from time to time.
Emigration of motile (locomotory) members of a population may occur in cases.
Immigration of motile (locomotory) individuals of other population may also occur in cases in quest of food or shelter.
Due to certain inter-relationships among the members of a given population, like – Competition for food or shelter, Predation, Grazzing, Parasitism etc. certain change can occur in the Biotic Factors of that population resulting in certain changes in it. These factors increases with the increase of the Population Density and are know as density dependent factors.
Certain drastic changes in the abiotic factors in the environment, like – light intensity, temperature, water availability, humidity of wind, can cause sudden death or destruction of a given community. These factors are not related to the population density and are termed as density independent factors.

Biotic Community

According to R. L. Smith (1966), “a biotic community is a naturally occuring assemblage of plants and animals living in the same environment and interacting in many ways, including mutualism, predation and competition”. In nature the biotic factors like – plants, animals and other living organism live together interacting with each other creating an adaptive sustainable condition. This includes interdependance, adjustment, tolerance and many inter-relationships like – Commensalism, Parasitism, Symbiosis, Mutualism and again in parasitism we see host-pest and predator-prey relationships. So, when a number of diversifies biotic factors interact and adapt within a given habitat type, forming an inter-related group, it is termed as Biotic Community.

The members of a biotic community live in the same eco-system and interact with each other, like – a forest, a savana, a grassland, a desert or a lake community. A biotic community can be divided into two major types, like – the plant community and the animal community. These two groups never compete with each other, rather they come as interdependant groups. The plant community survive through their anchorage by roots to the ground and draw mineral salts and water by them; they proliferate their group by means of seed dispersal or vegetative reproduction. On the other hand, animals depend upon plants or plant products for their survival; in some cases they are carnivores, insectivores or omnivores, but they have to depend upon plants directly or indirectly for their food or shelter and proliferate their number through different reproductive means.

Characteristics of a Community

The characteristics of a community are as follows –

Species Diversity – Due to the biodiversity of nature there exists a diverse number and category of Species within a biotic community, living together, competing for their basis needs and interdependant with some for those; like – Plants, Animals and Micro-organisms. We find a marked difference among them on the basis of their classification and number of individuals. This type of biodiversity can be local or regional as well.
Growth form and structure – Due to biodiversified life style the diverse members of the same biotic community exhibit a system in their organization on the basis of their inter-relationship; like – different zones of a given Pond eco-system; e.g., its Littoral zone, Limnetic zone and Profundal zone. All those zones maintain a strong bond with each other though diversified in their factors (biotic and abiotic) and inter-relationship of organisms. Some community can be known by its plant or animal groups present; like – Tree, Shrub or Herb community in plants as well as Lentic and Lotic community in animals.
Dominance – The presence of each Species in a biotic community is not equally important. So, a few of them exert dominance over others due to their number, size and ecological factors. Those are known as Ecological Dominant Species.
Succession – It is an important characteristic within a biotic community, as each community has its own way of proliferation and diversification. So, the succession of a biotic community occurs on the basis of a place, duration of time and condition. The significant causes include – climatic condition, competition, invasion, accumulation and ecesis (the adaptation of a newly introduced species with the existing situation) etc.
Trophic Structure – Each biotic community maintains is specific trophic structure and through this they maintain a balance in nature as a self-dependant and self-controled group.
Stratification – It is a significant characteristic in a plant community; e.g., there are three distinct layers within a grass-land (Savanna) plant community, like – a. Herbaceous Stratification, b. Floor Stratification and c. Sub-terranean Stratification.
Periodicity of Community – The structure and nature of plants changes in course of time, and never constant. Different plant community emerge at different time round the year, which shows difference in size, nature and number of them with the change of seasons and climatic conditions. For instance, the flowering in plants depend on seasons and same is the case with the avaiability of fruits; a result of environmental impact on plants. Same is the case with animal breeding, like – the Toad breeds at the end of Summer at the advent of a Shower (in the rainy season).
Relative Abundance – Different populations within a biotic community survives on the basis of their relative ratio, which is termed as Relative Abundance.

Types of Community

From the ecological point of view a biotic community can be of many types, like –

Ecological Niche community – On the basis of the ecological niche, a biotic community can be divided into three categories, like – a. Producers or Autotrophs, b. Consumers or Phagotrophs, and c. Decomposers.
Area based community – On the basis of area, a biotic community can be divited into – Desert Community, Forest Community, Fresh Water Community, Marine Community etc.

Besides, R. L. Smith (1977) divided the biotic community into two major categories, like –

Major Community – It is a very large community, completely formed and independant from any other adjacent community. The population number of plant and animal community members is much higher. e.g., Sundarban Mangrove community and Sahara desert community.
Minor Community – It is a small community, neither completely formed nor independant from the adjacent communities. e.g., a river community, a pond community, a lake community, a marsh or bog community. Even there are smaller communities as well, like – a micro-habitat, micro-organism floating of a leaf or a piece of log. Sometimes, a biotic community diffuses with its adjacent ones in such a way that there remains no boundaries or demarkation; these types are termed as Ecotones.

BIOMASS / BIOENERGY:

Biomass:

Living organisms are made up of various organic compounds like carbohydrates, fats, proteins, etc. All of them contain energy in their chemical bonds. The total organic matter (usually dry weight) of all living organism found in any given area, at a given time, is called biomass. The production and the ability to produce biomass depend upon the structural and functional components of an ecosystem.

Bioenergy:

The chemical energy present in the organic materials found in biomass is called Bioenergy. It has been estimated that one gram molecular weight of the organic matter of biomass (dry wt) contains about 42 K. Calories of energy. Such energy is called Bioenergy.

Biopotential:

In many ecosystems, the producers are consumed continuously. If this goes on without replenishment of additional producers the biotic components perish. However producers keep on producing more organic matter. Some produce more than the others. The ability of the plants to produce certain amount of organic components in a given time is called Biopotential. In this context the phytoplankton in aquatic systems have very high biopotential

TROPHIC LEVELS AND ECOLOGICAL PYRAMIDS

All the existing biotic components in any ecosystem can be grouped into producers, consumers and detritivores. Producers may be primary or secondary. Similarly the consumers can be grouped into primary, secondary and tertiary kinds. Each of them can be quantified in terms of number, biomass or energy. Such grouping is called Trophs and relationally they can be organized into trophic levels.

The graphic representation of trophic structure in the order of flow of energy from producers to consumers is called Ecological pyramids. They provide qualitative and quantitative information on numbers and biomass; and relationship with each other; so there can be a pyramid of energy, pyramid of number or pyramid of biomass. The most correct representation of an ecological system is by ecological pyramid of biomass. The others are inaccurate. The pyramid of number is also called Estonian pyramid. These can be applied to any ecosystem. The pyramid structure varies from one ecosystem to another ecosystem. Normally these are erect, but only aquatic systems show inverted pyramids.

FOOD CHAINS/FOOD WEBS

All autotrophic organisms which are capable of synthesizing their own food materials are called producers. They provide the food and act as the main source of energy for non producers, i.e., consumers. Among the producers there are two kinds, i.e., Primary producers and secondary producers. Similarly plant eating animals are called as herbivores and they act as primary consumers. Animals which eat other animals act as secondary and tertiary consumers.

Most of the free floating planktonic algae, epiphytic or lithophytic algae are generally considered primary producers. The terrestrial plants and their epiphytic or semi-parasitic green plants form secondary producers. In any given ecosystem the content and kinds of producers and consumers vary. But all of them exist in an equilibrium state. Such systems are referred to as stabilized ecosystems.

The organization of producers and consumers in a sequential order of flow of energy is called the food chain. It may be linear, branched or inter linked (food web). Most of the ecosystems show food chain in the form of food web.

Linear food chain: Organisms are arranged in the order of ‘ who eats whom. In all these cases, the starting point is the producer.

Grass -» Grasshopper -» Lizard -» Snakes -» Hawks.

Grass -» Mice -» Snakes -» Hawks

Grass -» Rabbits -» Dogs -» Tigers/Lions.

Trees -» Deer/Goats -» Foxes -» Tigers/Lions.

Trees -» Birds -» Snakes -» Hawks.

Phytoplankton -» Larvae -» Fishes -» Whales.

Food Web: Grass or its products are eaten by grasshoppers, mice, rabbits, deer, goats, etc. The grasshopper is eaten by lizards or frogs. Frogs are eaten by snakes or hawks. Similarly mice can be eaten by snakes or foxes. Foxes can be eaten by tigers or lions. The flow of bioenergy in such a system is not linear but interlinked and forms a kind of network called Food web. For that matter there is no ecosystems with only linear food chain, but all have food web systems.

Detritivores Food Chain: Unlike the above said food chains involving macro-organisms, there are other life forms called microorganisms which play a very important role in any given ecosystem. All dead plants or animals are subjected to organic decomposition by microorganisms. The released organic compounds are further converted to various other simple substances. This process enriches the soil or water. For example, proteins are degraded into amino acids, which are then converted into ammonia. The same can be further converted to nitrates or nitrogen oxides, which can be used by other forms of life. Each one of these steps is controlled by specific microorganisms. Such a series of conversions and converters form the Detritus Food Chain.

Ecological Pyramid

Within a Food Chain in any environment there are successive stratification, which are known as Trophic Levels. At the first level exists the Producer, at the second level exists the Primary Consumer, the third level consists of the Secondary Consumer and the next level consists the Tertiary Consumer. All those trophic levels can be grouped together on the basis of their biotic contents, which assumes a pyramidal structure. So, an Ecological Pyramid can be defined as the systematic arrangement of different nutrient trophic levels (energy, biomass or number) in a pyramidal form.

Types of Ecological Pyramids

Ecological pyramids can be of three categories, like –

Pyramid of Energy or Production rate – The pyramidal structure that represents the different energy contents of the trophic levels in a Food Chain of an ecosystem, is known as the Pyramid of Energy (production rate). It is obvious that, the producer level at the base of the pyramid contains the maximum energy, gradually decreasing on the upper herbivorous (primary consumer) and carnivorous (secondary and tertiary consumer) levels. So, this structural representation of the energy content, at different levels of production and consumption, in the form of a pyramid is known as the Pyramid of Energy.
Pyramid of Biomass – The biomass is the living weight of organisms at each trophic level. It also represents a pyramical structure in the food chain of an eco-system. For instance, the biomass of first trophic level (producer) is much higher than the biomass of the second (herbivore) and the third (carnivore) trophic levels. So, the large amount of biomass of the producer level and gradual decrease of biomass contents in the upper levels signifies a pyramidal shape to the representation. The total biomass content of a food chain existing within an eco-system can be measured through this type of pyramids.
Pyramid of Number – It is also known as Eltonian Pyramid. The number of members of the biotic community at different trophic levels is also related to ecological pyramidal structure. That means, in respect of number, like the other two pyramids, the pyramid of number exhibits a generalized tendency to show the stratification of trophic levels. In respect of number the profoundness of the producer exceed all other levels. In the same way, the number decreases gradually in the second and third trophic levels. So, in this way a pyramidal representation exhibits the real ecological scenario.

It is noteworthy, these pyramidal structures in the eco-system play vital roles in maintaining a natural balance. So, any significant change or distortion in the pyramid of number could be the cause of imbalance in nature.

ECOSYSTEM

All living and non living components present on this planet interact among themselves and exist together in a dynamic state. Such an organization or assemblage is called an Ecosystem. For that matter, the entire earth with all its components is considered as a giant ecosystem or giant Biosphere (bios=life, sphere = area occupied).

The ecosystem existing on this planet is very vast and varied, in their structure, components and functions. Based on the habitat and dominant life forms existing in a particular area different kinds of ecosystems have been identified.

CONSTITUENTS OF ECOSYSTEMS: Every ecosystem, big or small, is always made up of two major components – Structural and Functional.

A. Structural Components: They consist of living organisms and non-living structures. The former is called Biotic and the latter is called Abiotic. They exist together and interact with each other in building up or reclaiming the system.

i) Biotic components: All living organisms from plants to animals are included under biotic structural elements. This includes detritivores also. However the biotic components vary from system to system.

ii) Abiotic components: They are the inert matters found on earth. Soil and its constituents, water and its constituents, temperature of the atmosphere, rainfall, atmospheric moisture, gases, wind, light, etc, all form abiotic contents.

B. Functional Components: Living organisms and non living matter in any ecosystem do not exist in isolation and function at a time. Most of the abiotic constituents provide raw materials, energy sources etc., for the living organisms to consume and produce the organic matter.

The functional components are mainly the processes involved in the flow of energy (solar energy), from abiotic components (including nutrients) into biotic components (as biomass), from one biotic to another biotic system and lastly from biotic back to abiotic system.

The success of an ecosystem mainly depends upon the longevity (or half life) of the bioenergy retained within the biomass. The half life of the bioenergy in a biomass in turn is controlled by the rate of producer’s, consumer’s and detritivores activities and rate of their interaction.

The major functional process of an ecosystem is autotrophic mechanisms, by which Solar energy is converted into chemical energy as the main capital. Using such energy and other abiotic ingredients biomass is built up by respiratory and other metabolic processes, responsible for the growth in the biomass. Lastly the biomass (after death) is converted by various oxidative processes into basic abiotic ingredients and there is a net loss of energy in the form of heat, where all bio-geo-chemical cycles arc involved in it. In all those energy transformation, there is loss of energy in one form or the other, which obey the second law of thermodynamics. It is the functional process that ultimately determines the success of biosystem in an Ecosystem.

MAJOR ECOSYSTEMS

The ecosystem of the earth is very vast and varied. It is difficult to comprehend all the features as unity. We find some area of land covered only with water, in certain areas one finds vast terrains of deserts, forests, shrubs and rocks. Each of these areas has different habitat and different flora and fauna, but they exist in stabilized state. Based on the habitat, flora and fauna, the giant ecosystem is basically divided into Terrestrial ecosystems and Aquatic ecosystems.

Terrestrial ecosystems:

Terrestrial ecosystem and its structural and functional contents vary from region to region. A large area dominated by uniform vegetation with other flora and fauna in an equilibrated, but stable state are generally called Biomics. But the term biomes cannot to be applied to aquatic ecosystem because they are considered as higher categories.

Terrestrial ecosystem is further classified according to their three dimensional structure of the flora, such as height of the tall trees, number of layers of foliage and horizontal continuity of the foliage layers. The main terrestrial ecosystems are Forest, Woodlands, Shrub land, Grassland, Scrubland & Deserts

Aquatic ecosystems : Aquatic ecosystem is being the largest of all, occupying 75% of the earth area, and also having a uniform Vegetation over a long period of time, they are considered as higher category than the terrestrial biomes. They are further classified into Fresh water centric, fresh water lotic, Ensturics, Marine benthic and Marine Pelagic etc. Even the communities present in them are grouped as littoral, abyssal etc. In this manual a brief account of few ecosystems has been given.

1. POND ECOSYSTEM:

It is a fresh water ecosystem. The half life of such ecosystems ranges from a few hundred years to many thousands of years. Most of them are inland systems whose life span depends upon the area and magnitude. The structural and functional components vary from place to place, altitudes, temperatures, etc. Well established pond ecosystems exhibit a self sustained, self regulated but an evolving assembly.

Abiotic Components: The major component is water. Gases like oxygen, C02, NH3, etc., inorganic and organic nutrients and other components are in dissolved state. The pH depends upon the above said components. Water provides the habitat and the environment
Biotic components:

Producers: They are microphytic phytoplankton and macrophytic rooted plants. The phytoplanktons are floating algae like Volvox, Oscillatoria, Diatoms, Spirogyra, Zygnema, Hydrodictyon, Desmids, etc. The epiphytic ones are Ulothrix, Cladophora, etc. The macrophytes are rooted plants like Nelumbium, Nymphea, Blixa, Eicchornia, Pistia etc. At the margins of ponds, one finds Cyperaceae and other members of higher angiosperms.

Consumers: Among the primary consumers benthic zooplanktons are very important. Some of the benthic forms are associated with the living plants and some feed on the plant remains at the bottom of the ponds and act as detritus forms. Zooplanktons are Brachiopods, Euglena, Cyclops, etc.; secondary carnivores are insects and small fishes. Large fishes act as tertiary consumers. Microbes found in the pond decay the dead plants and animals, and enrich the pond system with organic and inorganic components. When pond ecosystem is organized into trophic levels, the ecological pyramid of biomass shows an inverted pattern.

Our country has a large number of such natural fresh water ecosystems, some are man made others natural and most these provide raw materials for hydroseric plant successions.

2. MARINE ECOSYSTEMS:

More than 70% of the earth’s surface is covered with seas. It is a huge mass of water. Indian subcontinent is surrounded by three seas i.e., in the East, South and West. Ocean water has more salt and it is denser than any fresh water. The marine ecosystem is one of the largest and the most stabilized ecosystems. Based on the place and environment these can be subdivided into small groups, because abiotic and biotic components vary from region to region.

Producers: They are mainly Phytoplanktons like diatoms, dinoflagellates and other floating algae. Epiphytic and lithophytic forms like red and brown algae are also found in large populations. Angiosperms are found only on or near the shores. Plants in oceans fix about 135 billion tons of carbon annually.

Consumers: The primary consumers most of the herbivores like crustaceans, mollusks and small fishes. The secondary consumers are hermit crabs, snakes, and markels. Etc. Big fishes, dolphins and whales form the tertiary consumers. Microbes as decomposers are also accounted as important components, for they decompose and enrich the water. Most of the biotic components are unique in the sense; they are structurally and physiologically adapted to salt water. The number and variety of organisms is astounding. In this system also the ecologic pyramid of biomass shows inverted structure.

3. FOREST ECOSYSTEM:

Forest ecosystems cover nearly 25-35% of the total terrestrial or the land area. In India, 1/10 of the land mass is covered with forest ecosystems of different kinds. Forests are considered as the wealth of a country.

Forest ecosystems are further divided into biomes i.e., Tropical Rain forest, Tropical deciduous forest, Temperate rain forest, Temperate deciduous forests, conifers etc. In India all the above kinds are found. Among the above, tropical rain forests are very rich in soil nutrients and has highest number of species (plant & animal communities) in a given area. Though their location and biotic components vary from each other, they are self maintained systems. Most of the mountain tracts in India have forest ecosystems of one kind or the other. Western ghats and Himalayan ranges are abound with such ecosystems. Unfortunately most of the forest systems have gone.

Abiotic components: The abiotic components are soil, water, air, sunlight. Soil is very rich in inorganic and organic nutrients. The microorganisms found in the soil produce lot of organic matter.

Producers: The primary producers are mainly tall trees. There are some shrubs also. Some herbal flora consisting of ferns, mosses, lichens, etc. also dominate the forests. The trees are Tectona, Macaranga, Shorea, Tecoma, etc.

Consumers: The primary consumers are insects, mites, beetles, bugs and ants. Elephants, deer, bisons, goats, sheep also form such community. Secondary consumers are lizards, birds, snakes, foxes, etc. The tertiary forms are lions, tigers and panthers.

4. DESERT ECOSYSTEM:

Nearly 17% of the land mass whose annual rainfall is less than 25cm is a desert. In spite of hostile environmental conditions, certain organisms have established and stabilized in this environment into a self sustaining ecosystem. The abiotic factors are sandy soil, rocks, high temperature, abundant sunlight, wind, etc. The producers are mostly xerophytic shrubs and herbs. For example, canthium, cacti, agave and other succulents. Consumers are mice, birds, camels, snakes, etc. Decomposers also play an important role in a desert ecosystem.

5. GRASSLAND ECOSYSTEM:

Producers: In this kind of terrestrial ecosystem the dominant flora is grass a C4 system. They are the main producers and very efficient than C3 plants. Here and there other shrubs and small trees are present, but they are in minority.

Consumers: The primary consumers are grass eating insects, mice, etc., which are then consumed by the secondary consumers like lizards, snakes, etc. They are then eaten by the tertiary consumers like hawks and eagles. The microbes found in the soil also contribute to the ecosystem by enriching the soil with organic matter. It is important to remember that the producers dominate the flora and fauna many thousand times over. And they are the most efficient producers in terms of capturing energy and fixing carbon into energy rich organic matter. Such an ecosystem has climatic vegetation.

BIO-GEO-CHEMICAL CYCLES:

All ecosystems contain a wide variety of biotic and abiotic components and they exhibit one or the other functions. Using various minerals nutrients, water, C0₂, nitrogen, light energy, plants build up the organic matter. Continuous use of the above said materials depletes the components from the soil, water and air in course of time.

Consumers use the plant products and during oxidation they convert some organic matter into C02 by respiration. Also they release ammonia. etc., back to the soil or to the atmosphere. The death and decay of the plants and animals also leads to release of nitrogen, phosphorus and other components back to the soil. Thus they enrich the soil.

This kind of recycling of various abiotic components from soil, water and air into biomass and from biomass back into soil, water and air is called bio-eco chemical cycles. Water cycles, CO2 cycle, Nitrogen cycle, Sulphur cycle, Phosphate cycle are some of the examples of bio-geo chemical cycle.

Adaptation of Organisms

Adaptation is the capability or changes of an organism to synchronize with its ever changing environment. All Flora and Fauna exhibit the quality of adaptation to their changing surroundings.

Adaptation of Plants

Based on soil water, Warming (1909) categorized plants into four types, like –

a. Hydrophytes (Aquatic plants),
b. Xerophytes (Desert plants),
c. Mesophytes (Normal plants) and
d. Halophytes (Mangrove vegetation).

Hydrophytes (Aquatic plants)

The plants which usually grow in water are known as Hyrdophytes. They are again of three categories based upon their environment, like –

Floating Hydrophytes – Those are plants which completely float on water and can again be divided into two types, like –
a. Free Floating Hydrophytes – They are totally free floating with no connection to the soil. Small plants like – Guripana (Wolffia), Khudipana (Lemna), Topapana (Pistia), Kochuripana (Spirodella and Eichhornia) are included in them. Besides, there are Bryophytes like – Riccia fluitans and Pteridophytes like – Azolla and Salvina etc.
b. Rooted Floating Hydrophytes – They are attached to the ground through their roots but their leaves and flowers float on water; the leaf petiole and the flower peduncle are as long as the water level, which help the leaves and flowers float on water due to the presence of spongy tissue in them. Examples are – Water Lily (Nymphaea), Lotus (Nelumbo), Singara (Trapa), Makhna (Apomogeton and Euryale), Limnanthemum, Victoria etc.
Submerged Hydrophytes – Those are plants which remain the total life under water and never come to the surface level. Flowers, fruits and seeds are hardly found in these plants and they can again be divided into two types, like –
a. Submerged Floating Hydrophytes – They are totally free floating but under water and can move with water current and have no connection to the water bed as they are devoid of roots. Examples are – Jhanjhi (Utricularia), Ceratophyllum, Najas etc.
b. Rooted Submerged Hydrophytes – They alway remain under water and are attached to the ground through roots at the primary stage of their life but later they detach from the water bed and float under water. Examples are – Hydrilla, Vallisneria, Potamogeton, Isoetes, Chara, Nitella, Elodea etc.
Amphibious Hydrophytes – The plants which grow with their some part in water but other outside of it are termed as Amphibious Hydrophytes or rooted emergent hydrophytes. They remain attached to the water bed through their roots but a part of their stem with leaves are left exposed outside the water. Examples are – Helencha (Enhydra flactuans), Kolmilata (Ipomoea aquatica), Keshordham (Jussiaea repens), Hogla (Typha), Pani Morich (Polygonum), Nol Khagra (Phragmites), Clinogyne etc.

Adaptation of Hydrophytes

The adaptations of Hydrophytes are as follows –

Morphological Adaptations –

Roots, very limited, weak and unbranched (e.g., Hydrilla); never branched and even absent (e.g., Wolffia, Utricularia, Salvia, Ceratophyllum); in some cases the submerged leaves act as roots (e.g., Salvia).
Roothairs, absent; devoid of rootcaps, with root pockets instead (e.g., Eichhornia).
In cases the adventitious roots form floating roots, e.g., Keshordham.
In submerged hydrophytes the stem is flexible, elongated and spongy (e.g., Hydrilla, Potamogeton).
In floating hydrophytes the stem is short, slender, spongy, with Stolon and Offset (e.g., Eichhornia, Lemna).
In some hydrophytes the stem is juicy and Rhizome-like (e.g., Nymphaea, Nelumbo).
The modified stem undergo vegetative reproduction.
Leaves can be elongated, thin and tape-like (eg. Vallisneria); elongated and linear (eg. Potamogeton); leaf lamina fragmented (eg. Ceratophyllum); leaf multi-fragmented (eg. Myriophyllum); large, flat and spherical (eg. Nymphaea, Nelumbo); much bigger, even to hold on a small baby. eg. Amazon Lily (Victoria amazonica).
In cases (e.g., Nymphaea, Nelumbo), leaves are coated with waxy materials, to avoid wetting or rotting.
In cases (eg. Ranunculus, Sagittaria), leaves are of three types – submerged, floating and areal.
Submerged leaves are usually translucent.

Anatomical Adaptations –

Cuticle, either absent or very thin and weak.
Epidermis, thin walled, one layered and made up of parenchyma cells; Chloroplasts presents on the epidermal walls in submerged hydrophytes.
Cortex, well-developed with Arenchyma cells; provided with air-chambers in maximum places, which protect the curvature due to strong air pressure, increases the buoyancy and help in gaseous exchanges.
Vascular tissues are weakly formed and unclear in floating and submerged hydrophytes, but are well-developed in amphibious hydrophytes.
Mechanical tissue and Hypodermis are totally absent.
Stomata, absent in submerged hydrophytes, present on the leaf-surface of floating ones, but are present at both surfaces of amphibious hydrophytes.
In submerged hydrophytes the Mesophyll tissue of the leaf is not divided into Pallisade and Spongy parenchyma; but in floating hydrophytes it is.
The stem and leaves are provided with waxy materials which protects from putrification.

Physiological Adaptations –

Reproduction is usually of Vegetative form.
Transpiration rate is very low; in cases water perculation is done through Hydathodes.
Putrification is protected in Hydrophytes due to the presence of Mucilage.
Water is absorbed throughout the body; roots or root hairs are not formed for it.
Growth rate is usually low.
The air chamber in the cortex helps for buoyancy to support floating.

Xerophytes (Desert plants)

The plants which usually grow in sandy, arid, rainless areas are known as Desert plants or Xerdophytes. The areas where the precipitation rate is very low are also seen to have this type of vegetations. That means the area where the water supply is very low but transpiration rate is very high will have xerophytes. Oppenheimer (1960) described Xerophytes as plants which can bring changes in their external and internal morphology as well as physiology to meet the scarcity of water in their habitats. They are mainly divided into the followign four categories.

Drought escaping plants – Usually these plants are annuals or biannuals. They grow quickly under favourable condition and complete their life cycle very shortly. In an unfavourable situation their upper part outside the soil dies out but leaving alive the underground part, which grows again under the next favourable situation. In this way they escape the draught. Examples are plants of Family – Asteraceae, Boraginaccae and others.
Drought evading plants – These plants are smaller in size and their growth is limited. They restore in their body the water found in favourable condition and technically overcome the draught using that. e.g., Protulaca.
Drought enduring plants – These plants grow very little in one season, so they grow into stunted shrubs. They start wilting their leaves according to shortage of soil water, which ultimately shed off. In this way they can withstand the scarcity of water in the soil for a longer period of time. Their physical growth resumes after the unfavourable situation is over. Examples are – Calotropis, Nerium, Euphorbia, Acacia etc.
Drought resisting plants – Those are real xorophytes or desert plants. The collect water from the rain that occur only once or twice a year; they collect it through their extended rooting system and store it in their leaves. So, they bear succulent stem and leaves, which help overcome them the draught when the soil water is very scarce. In this way growth never stops, but continues all over the year even during a strong draught. Examples are – Opuntia, Euphorbia, Protulaca, Agave, Aloe vera etc.

Some Ecologists classify the Xerophytes into three groups based upon their physical structures, like –

Ephemerel Annuals – They are drought escaping plants, grow in dry temperate zones and have very short life cycle. They exist at best 6-8 weeks, like – Shialkanta (Argemone).
Succulents – They are succulent plants which reserve water within their body in their leaves and stem to face the drought. Examples are – Aloe, Euphorbia, Opuntia, Asparagus etc.
Non-succulent perennials – They are true xerophytes; capable to protect the drought. Their leaves are replaced with spikes that reduce water loss through transpiration. Examples are – Acacia milotica, Zizyphus jujuba, Calotropis procera, Phoenix, Nerium etc.

Characteristics of Xerophytes

Their roots are extended and deeply embedded in the ground.
Usually the cellular structure is smaller.
The cell wall is thick and provided with cuticle.
Intercellular space is rare.
The Palisade parenchyma is well-developed and stout.
The Stomata are sunken and exist at the endodermis.
The stem grows into a green, succulent and flattened structure.
The leaf is in many cases replaces by a thorn.
The epidermis is thick and many layered.
The surface of the leaf and stem is provided with waxy materials.
In many cases the leaves are coiled up or closed.

Adaptation of Xerophytes

The adaptations of Xerophytes are as follows –

Morphological Adaptations –

The rooting system is well-developed, broken in secondary and tertial branches, which expand in area and deeply penitrate the soil in quest of water.
The main root divides into secondary and tertial roots and each root is provided with root hairs and a root cap.
In maximum cases the stem is short, strong and woody, covered with a thick bark.
Some of the stems are Phylloclades, which are green, flattened, succulent and leaf-like (Opuntia); in cases, succulent and green but not leaf-like (Euphorbia).
The stem is usually covered with hairy outgrowths or waxy materials.
Leaves are very limited and are modified into spikes, which reduces the rate of transpiration (eg. Opuntia); leaves which are not modified like this are thick and succulent, or are hard and hide-like.
Leaves are coiled or folded in some plants; in cases, the stipules turn into spikes (eg. Acacia, Zizyphus etc.), or in some they turn into needles (eg. Pinus)
The leaf surface is bright and shiny, thus can reflect out light and heat.

Anatomical Adaptations –

Roots, well developed, with root hairs and root cap; epiblema thick; some are succulent (eg. Asparagus)
The vascular bundles and mechanical tissues are well developed and deposited with Lignine.
The hypodermis of succulent stems contain tissues for water retaining.
Mucillage is present in some plants like Aloe in their epidermal cells.
Heavy cuticular coating is present on the epidermal lining of unsucculent plants.
Their stomata are sunken and the stem is covered by long, dense hairy outgrowths or heavy cuticle.
The mesophyll tissue retains water and make the leaf succulent (eg. Aloe); Epidermal cells of some plants retain water (eg. Peperomia).
The mesophyll tissue is well defined in Pallisade and Spongy parenchymas with little intercellular space.
The epi- and hypodermis of leaves of certain plants like – Nerium are multilayered.

Physiological Adaptations –

Plants are shorter due to stunted growth.
The rate of transpiration is very low due to thick epidermis as well as sunken Stomata covered by hairy outgrowth.
The transpiration rate is also very low as the leaves are replaced by thorns or spikes.
The enzymatic activity is hampered due to scarcity of water in the cell.
Due to the high density of cell sap, leaves can not dry up usually.

Mesophytes (Normal plants)

The plants which grow on soil where the soil water is normal (neither more nor less) are known as Normal plants or Mesophytes. A normal temperature, humidity and tropical climate is necessary for the growth and development of such plants. They can not grow in water logged soil or with increased salinity in soil water. They grow better on alkaline humous soil, like that in Bangladesh.

Characteristics of Mesophytes

Their roots are well developed with secondary and tertiary branches; root hairs and root caps are present.
The stem is usually areal and branched.
Leaves are large and wide with different formations; never coated with hairy outgrowths or waxy materials.
The epidermis contains normal cuticular lining; devoid of any chloroplast.
Stomata are present on both sides or a single side of leaves; never sunken.
The mesophyll tissue is divided into Pallisade and Spongy parenchyma in Dicots but undivided in Monocots.
The vascular bundle and mechanical tissues are well formed.

Halophytes (Mangrove vegetation)

The plants which grow on soil where there is salinity in the soil water are known as Salty soil plants or Halophytes. They can not absorb water from the soil due to the presence of dissolved salts (NaCl, MgCl₂, MgSO₄) in it; so, special type of plants grow in there, and the soil like this is termed as Physiologically Dry Soil. Therefore, the Halophytes resemble the Xerophytes in many respects. Some scientists have names the Halophytes as Xerophilous plants, due to their physiological and physiographic relation to the Xerophytes. The Halophytes which grow on the coastal zones and tidal areas are know as Mangrove plants. The southern and south-western part of Bangladesh contains the largest Mangrove vegetation in the world, the Sundarbans. The Halophytes can be divided into four categories, like –

Lithophilous Halophytes – Plants which grow on stones or pebbles of the salty soil or halophytic zone.
Psammophilous Halophytes – Plants which grow on sandy soil area of the salty soil or halophytic zone.
Pelophilous Halophytes – Plants which grow on clay soil area of the salty soil or halophytic zone.
Helophilous Halophytes – Plants which grow on saline water area or salty desert area of the halophytic zone.

Characteristics of Halophytes

They can be annual or perrenial; herbs, shrubs or trees.
Leaves are thick, small and hide-like.
They produce breathing roots with respiratory pores (pneumatophore) in the as breathing of roots is hampered without them in the coastal salt water zone, where places are intercepted by daily tidal water.
Plants exhibit viviparous germination to cope up with the daily up and low tide that swap every 12 hours.
Plants also produce stilt roots for a better anchorage to the salty clay soil, intercepted by daily tides.

Adaptation of Halophytes

The adaptations of Halophytes are as follows –

Morphological Adaptations –

Plants are usually tomb-shaped and their hight is less.
Leaves are thick, succulent, smooth and shiny.
They produce breathing roots with respiratory pores (Pneumatophores), to meet the scarcity of O₂ under the salty soil of the tidal zone.
They produce stilt roots or root butress to get a better anchorage in the claye subtratum of the salt water zone.

Anatomical Adaptations –

Cells of leaves contain a huge amount of cell sap.
The amount of Chlorophyl within the cell is less.
Mucilage cells are present within the green tissue.
Pallisade tissue is well developed with very less intercellular spaces.
The dermis is fortified with heavy cuticular or waxy linings.
The vascular and mechanical tissues are well developed.
Stomata sunken and present only in the endodermis.
The cortex is provided with star-shapped lacoonoid cells.
Cells retain oil and tenin.

Physiological Adaptations –

The growth of salty soil plants or halophytes occur in the rainy season.
The roots breathe through fine pores or pneumatophores of their breathing roots, raised above the water or clay level.
The seeds exhibit viviparous germination to cope up with the daily tidal saline water that swap over the forest floor twice a day.

Mangrove Vegetations

The plants that grow permanently in the soil of the tidal zone are known as Mangrove plants. They are special types of Halophytes which grow in salty and claye soil. The forest floor is subjected to the coastal up and low tides that swap twice a day indulging the plants to exhibit viviparous germination and washing away a part of the newly growing saplings. The southern part of Bangladesh have this sort of forest, largest in the world, in the Sundarban and Chokoria Sundarban areas.

The plants are not much higher and their leaves are smooth and shiny. Some of them produce stilt roots that help them stand erectly on the claye forest floor. The lower part of plants remain under water or clay all the time and can not breathe due to scarcity of O₂; the phenomenon is termed as Physiologically dry. To cope up with this situation plants produce breathing roots (with pores or Pneumatophores), which grow above the water or clay level and help them brethe easily.

In the viviparous type of germination the seeds grow into saplings, i.e., develop their Radical and Plumule, being inside the fruit which is still attached to the plant. The Radical grows enormously to get a better anchorage to the claye soil of the forest floor when the sapling drop down and grow roots very quickly during a low tide. Though during the following up and low tides some of the newly dropped saplings are washed away, still the number of newly grounded plants is good. This is a natural process through which a mangrove forest retains its entity and grows further towards the coastal margin. This type of forests are found in Bangladesh, India, Madagascar, Malaysia, Western coast of Africa, Eastern and Western coasts of America as well as in some Pacific peninsula.

The common plants of Sundarban includes, Sundari (Heritiera fomes), Goran (Ceriops roxburghii), Gewa (Excoecaria agallocha), Poshur (Carapa moluccansis), Kewra (Sonneratia apetala), Bora (Rhizopora conjugata), Hargoja (Acanthus illicifolius), Golpata (Nipa fruticans), Kankra (Bruguiera gymnorhiza), Bina etc. Among the animals are, world renowned Royal Bengal Tiger, Spotted Deer, Monkeys, Crocodyles, Tortoise and Turtles, Wild bores, King Cobra and other Sankes as well as different species of Birds, Frogs, Bees, Insects and more than a hundred species of fishes.

Adaptations of Mangrove Vegetation –

Plants are usually tomb-shaped; less in hight; produces stilt roots for a better anchorage to the claye soil.
They produce breathing roots with pneumatophores (fine breathing pores) which grow above the soil or tidal water level and help brethe the roots, as the salty soil contains very less O₂, unsuitable to brethe inside it.
The plants undergo Viviparous germination and germinate their seed inside the fruit which is still attached to the plant. The Radical grows enormously taking a slender and heavy shape that helps it to fall directly to the claye salty soil and deeply penetrate it for a better anchorage; roots grow very fast and grasp the soil before the following uptide. In this way the forest retains its integrity and grows further towards the coastal margin.

Xerophytic Characteristics of Mangrove Vegetation –

Plants are usually tomb-shaped and their hight is less.
Stems are succulent; leaves are linear, succulent or hide-like.
The Dermis is very thick and with Cuticle.
The Stomata are sunken and only present in the endodermis.
The mesophyll tissue is divided into Pallisade and Spongy parenchyma, which are devoid of intercellular spaces.
Many of the species produce Mucilage cells.

Importance of Mangrove Vegetation –

Mangrove vegetation acts as a protective device against Tidal bores, Surge, Cyclones and many natural calamities.
Their stilt roots and breathing roots act as a very good anchorage device against the soil erosion during a natural calamity or regular tidal pressure.
The leaves are taken by a lot of animals as food and the dry ones along with dry branches and twigs are used as fire-woods.
The stem of many species produce log-wood valuable for housing purpose or boat preparation; used as fire-wood in cases; stilt roots are used for anchorage of boats.
Some of the soft woods are used as raw materials for Newsprint paper industries.
Many of the plants (like Golpata) are used for thetching purpose and their fermented lequor is drank as stimulant.
Barks of some plants are used for tanning (fishing nets of the fishermen) purpose.
Tenin out of these plants in America and Europe is now used in the tennary industries and very recently the Tenin Formaldehyde Resin, produced out of it is used for attaching Plywood sheets.
The mangrove vegetation is the habitat for inormous number of individuals including world renowned Royal Bengal Tiger, which help retain a very naturally balanced biodiversity, sustainable for future.

Biomes

The major and isolated ecological zone with the same soil type and climatic condition, having animals and plants with specific characteristics, is called a Biome. We can call a specific geographical area as a Biome, with specific soil type, animals, plants and their eco-systems interacting under similar climatic condition. A Biome is formed with a number of Communities, where each and every animal and plant is its member. The total world is divided into a number of Biomes, which can be of the following types –

Terrestrial Biome – It can be grouped into the following types –

Tundra Biome
Grassland Biome
Desert Biome
Savaanah Biome
Forest Biome

Aquatic Biome – It can be grouped into the following types –

Fresh Water Biome
Marine Biome

Terrestrial Biomes –

A. Tundra Biome

The Tundra Biome is formed with the Tundra areas (ice-covered and plantless) of the world.

Geographical Location – Northern part of Siberia in Russia, Greenland (residing place of Eskimos), Alaska, landmass related to the North pole (Arctic region).

Salient Features of Tundra region –

The very cold situation is the main feature here.
The soil remain snow casted most of the time of a year.
The Summar is only for 60 days, but the plants complete their life cycle within this period.

Plants of Tundra region – A huge amount of Lichens are found here. Besides, there are Mosses (Bryophytes), a number of Shrubs and trees with very small and limited branches.

Animals of Tundra region – A number of mammals (homeothermic) are found here, like – Reindeer, Polar Bear, Jackel, Rabbit etc. A few migratory birds are found during the Summar along with a lot of Mosquitoes and Flies. The birds include – Penguines, Whistling Teals, Loons, Shikras, Zigars, Sandpipers, Owls etc.

B. Grassland Biome

The Grassland Biome is formed with the grassland areas of the world where the annual rainfall is 10-30in. So, the real forest or other vegetaions can not grow in such scarcity of water, but the area does not develop even in to a desert, as there is some water in it. As a result, different grasses grow here enormously.

Geographical Location – American Prairies, Grasslands of Argentina, Australia and Southern part of Russia are noteworthy.

Salient Features of Grassland region –

The soil is fertile and enriched in Humus.
The nutritive materials never wash out as the precipitation rate is lower.
The diurnal and noctarnal temperature variation is minimum.
The temperature limited within 15^O – 30^O C during the Winter and Summar.

Plants of Grassland region – Grasses of different type are the main vegetation. Grasses of two types grow here – a. Long Grass (5′-6′ ft.) and b. Short Grass (less than 5′ ft.). Besides, Wheat, Corn, Maize etc. grow better.

Animals of Grassland region – A number of herbivores are found like – Bisons, Antelopes, Zebra, Jirraf, Wild Horse, Kangaroo, Deer etc.

A number of carnivores are also found like – Lions, Cheetas, Hayenas, Jackels etc. Besides, Different species of Birds, Snakes, Lizards and Frogs are also found. Insects, Locusts, Bees, Grasshoppers, Flies, Butter flies and Termites are found among the Arthropods.

C. Desert Biome

The dry Biome where there is maximum scarcity of water is the Desert Biome. It is almost lifeless zone of the world, where the soil is dry and sandy with a little precipitation all over the year; animals and plants are very limited.

Geographical Location – South American Idaho, Chili, African Sahara, Asian Gobi, Indian Run of Cutch in Rajsthan, Arabian deserts, Argentinan deserts, Australian and Tasmanian deserts are examples.

Salient Features of Desert region –

The is always very hot and the presence of natural water body or temporary water holes are absent.
The annual rainfall is very irregular and less than 10′ in.
The variation of diurnal and nocturnal temperature is maximum, i.e., the day is very hot and the night is very cold; in some the temp. raises even upto 182^OF by the day and lowers down below the freezing point by the night.

Plants of Desert region – Special types of vegetation grow in this region due to the scarcity of water, like – Cactus, Dates, Babla etc. In some places grasses are also seen. The leaves and stem of Cacti are succulent to retain water for needfull situations.

Animals of Desert region – Among the mammals are found – Camels, Dumba, Kangaroo, Jackel, Rabbits, Rats etc. Among the birds are found – Vultures, Shikras, Eagles, Turkys, Honey birds, Ravens etc. Among the reptiles are found – Horned Lizards, Gila Monsters, Side winder and Coral snakes. Among the invertebrates, Spiders, Scorpions, Bees and other insects are found.

D. Savaanah Biome

Savaanah is a Spanish word meaning large treeless open grassland. The Spanish settlers of the South America called the grasslands there like this. Today the tropical grasslands are called Savaanahs.

Geographical Location – It is present in the Crescentic Congo Basin of Africa. It is situated in between the Sahara Desert and the Temperate forests of the Congo Basin.

Salient Features of Savaanah region –

Three seasons – Winter, Summar and Rainy seasons, are seen here.
The winter is rainless, the Summar is with a little rain; the amount of precipitation is 10′-60′ in.
The herbaceous plants grow plantiful, due to the low precipitation rate.

Plants of Savaanah region – Though the main vegetation is the the grass, yet Oats, Bazra, Wheat etc. are cultivated. Besides, Babla, Euphorbia and Palm-like plants are also found.

Animals of Savaanah region – Among the animals are found herbivores like – Antelope, Zebra, Jiraff etc. and carnivores like – Lion, Cheetah, Hayena etc..

E. Forest Biome

The forests of the world constitute the forest biome; but forests vary so much with each other in their soil contents, climatic conditions, altitude and organic contents that, they can hardly be kept under one head. They vary from each other even within a country and so are they named differently, which is described below –

Coniferous Forest Biome –

It is an evergreen forest; plants retain their leaves all over the year. Many of the basins and terrains in the North America contains this forest. Besides, they are common in the tropical regions of the world.

Pines, Furs, Spooges etc. Gymnosperms are the main plants and animals found are – Bears, Foxen, different species of birds, a few reptiles and amphibians as well as many types of insects.

Deciduous Forest Biome –

The characteristic feature of this forest is that it sheds off leaves at the advent of winter every year. The fallen leaves fall to the forest floor and enrich it in its organic contents. A few evergreen plants are also found here. Many countries in the South Asia, South Ameica, Europe, Japan and Australia contains this type of forest.

The main plants are – Asian Shal, Gajari, Beech, Oak, Maple, Hickory, Chestnut etc. Besides, a number of vines and shrubs grow along. Main animals are – Deer, Bear, Camel, Jackel, Squirrel, Forest Cat, different species of small and hunting birds, a few amphibians etc. Beside, a lot of invertebrates inhabit these forests.

Tropical Rain Forest Biome –

It is a dense and evergreen forest, enriched in big trees. A few deciduoud plants are also found along. These forest face rain most of the time in a year and so the forest floor is alway wet, damp and muddy. The Amazon, Congo, Jambessy river basin and areas of central America, Malay, Borneo and New Guinea are these type of forests.

The main vegetation constitute large evergreen trees. Among the animals, Monkeys, Anteaters, different species of Birds, Reptiles, Amphibians, Termites, Snails, Slugs, centipeds, Leeches etc. are common.

Evergreen Forest Biome –

Evergreen forests are basically tropical rain forests. They are very resourcefull.

Geographical Location – This type of forest is found in the South American Amazon vally evergreen forests, locally known as Selva; African Congo Basin (upto Madagascar); Temperate moist areas of South-East Asia (from the Himalyan Mountain range at the North, Indochina and Phillipines at the North-East, Malay, Indonesia and New Guinea at the South-East upto Fiji Islands).

Weather of Evergreen Forest region – The annual mean temperature of the tropical rain forests vary from 25^OC – 27^OC; mean Humidity is about 95% and the annual precipitation rate is 80′ – 100’in.

Plants of Evergreen Forest region – Plants found in these forests can be stratified into three canopies on the basis of their hight, like – the very tall plants or Top Canopy (ranges from 100-200’ft), the medium tall plants or Middle Canopy (ranges from 50′-125’ft) and the moderate plants or Lower Canopy (ranges from 20′-50’ft). Besides, the forest floor is enriched with vines and herbs of various kinds. Among the plants are – Jamba, Fig, Black berry, Forest Coffee, Iron wood, Red and White Kopal, Maya, Mehgani, Kanchan, Palm, Rubber, Ethio Palm, Garjan, Shal, Loona, Shil Koroi, Chapalish, Gaab, Jarul, Kadamba, Sandal wood, Udal, Shimul, Shegun, Arjun etc. Besides, there are plenty of Mosses, Lichens, Ferns, Epiphytes and the largest flower of the world – Rafflesia manillana.

Animals of Evergreen Forest region – A very good population of animals are found in these forest like – Monkeys (about 100 speceis), Big Cats (like Jaguar), Birds of Prey (Eagles, Shikras, Falcons etc.), Parrots etc. Besides, a huge number of invertebrates inhabit these forest and enrich them with organic contents, like – Snails, Slugs, Earthworms, Termites, Mosquitoes, Flies, Ants, Moths and other innumerable number of insects.

Mangrove Forest Biome – (Described elaborately earlier.)

Forest areas of Bangladesh

Bangladesh is a SAARC country situated in the south-east Asia with an area of 1,44,000 sq.km. To the north is the Kunchbihar and Jalpaiguri districts, Meghalaya and Assam state of India; to the east is Assam, Mizoram and Tippara state of Indian and Myanmar; to the west is the West Bengal and to the south is the Bay of Bengal. The total country has been formed from the alluvial plains, slanting from north to south, intersepted by mighty rivers Padma, Jamuna, Brahmaputra, Meghna and their tributeries. The total country is a plain land except Khagrachari and Bandarban districts of Chittagong hill tract, Cox’s Bazar, Chittagong and parts of Sylhet district. It extends from Latitude 20.5⁰ N to 26.5⁰N and Longitude 80⁰ E to 92.5⁰ E. The Tropic of Cancer has crossed through the southern part of Comilla town, which can be identified by Tomsom Bridge of British period, that still carry the plaque.

Though Bangladesh falls under the temperate zone, yet the influence of Monsoon air is much on it, with an annual precipitation about 200cm. and an average temperature from 24.5⁰ C to 26.5⁰ C. So, a moist climatic condition exists here most of the time. Based on the terrestrial and climatic condition the total country has been divied into five forest types or floro-geological areas, like –

a. Deceduous forest types,
b. Mixed (semi-evergreen) forest types,
c. Evergreen forest types,
d. Padma-Meghna alluvial plains and
e. Tidal forest types.

Deceduous forest types –

The plants of this type of forest carry green shiny leaves all over the year, but shed all of them at the advent of winter, when the branches become totally barren. After the winter is over new foliage grow with the first shower of rain. This forest type grows in high plains or on small hillocks around a hilly area. There are two such types in Bangladesh, like –

Dinajpur-Rangpur Forest type – Deceduous forest is found in Dinajpur, Rangpur and Rajshahi districts. The total area is known as Barendra Bhumi. The main plant is Shal and so people call those as Shal Ban or Shal Bithi. The main plants of these forests are – Gajari Shal (Shorea robusta), Bija Shal (Pterocarpus marsupium), Jackfruit (Artocarpus heterophyllus), Koroi (Albizzia procera), Babla (Acacia nilotica), Katechu (Acacia catechu), Black berry (Eugenia jambolana), Mango (Mangifera indica), Sonalu , Kumbhi leaf, Sagal boti, Kurchi, Shewra etc.
Gazipur-Tangail-Mymensingh Forest type – This forest type is situated on the hillock area of Gazipur, Tangail, Mymensingh and Sherpur districts. The soil is dry, red, humous and fertile, so there are crop lands around and in between these forest types, where people grow crops, especially paddy. People call the hillocks as Chala and the crop lands as Baid and the forest type is known as Modhupur Garh or Vawal Garh. People never need to apply any fertilizer to their baids, as the forest nutrients leech through soil to the crop lands along with rain water. The forest soil looks red due to the presence of iron compound in it, known as Podjol or Laerite soil. 95% of plants in these forests are Shal, a few are Koroi and other plants. General people call them Gazari Shalban; following is a description of some of them.

Vawal-Rajendrapur Shal forest – It exists at Gazipur district 75 km. north to Dhaka city. The forest is divided in Chala and Baid; the Chala forest is again two layered. The bitop of Gajari Shal is developed from the coppice. More than 95% of the vegetation is Gajari Shal (Shorea robusta), other plants are – Koroi, Jackfruit, Sonalu, Amalaki, Shimul, Assam vine, Datan, Gamari etc. Besides, there are Bamboos, Canes, Grasses and Epiphytes.
Chandra Shal forest – It is situated at Gazipur district, 45 km. north to Dhaka city. The main vegetation is Gazari Shal and like others the forest is divided into Chala and Baids. The soil is red, humous and muddy. Other plants are – Anantamul (Hemidesmus indicus), Asparagus (Asparagus racemosus), Jarul (Lagerstroemia flosreginie), Bija Shal (Perocarpus marsupium), Kurchi, Bohera, Koroi, Wood apple, Banaraj, Kumbhi leaf, Assam vine, Datan etc.
Modhupur Shal forest – The eminent Modhupur Shal forest is situated in Tangail district, a part of Gazipur and Mymensingh districts are also included in it. This rectangular forest extends about 100 km. north to south and another 50 km. east to west. Like other deceduous forests it is also formed of numerous hillocks and low lying terrains; the soil is red and hard, but very muddy during rains. The annual mean precipitation is 200 cm. The hillocks are full of Shal plants while the terrains are cultivated for crops. Other plants present along with Shal are – Asparagas, Chopra potato, Shal pani, Chalta, Datan, Kurchi, Amalaki, Arjun, Shonlu, Monkanta, Shil Koroi etc.
Rangtia Shal forest – It is situated at the norther side of Sherpur district, formed of a few hillocks of different sizes. The hillocks are full of Shal plants; other plants are – Chakra, Alpai, Banraj, Kumbhi leaf, Chalta, Assam vine, Syamdulan, Dhamin, Kurchi, Shial Kanta, Piralo, Shimul, Bohera, Bon neel, Ban kewra, Nishinda, Dhani, Bokul etc.
Gazni Shal forest – This forest type is situated at the north of Sherpur district and 9 km. west to Rangtia forest. The main vegetation is Shal in the hillock encircled area. Plants found in Rangtia forest are also found here.
Lalmai Shalban Bihar – This shal forest is situated 8 km. west of Comilla town. The main vegetation is Shal in the red-yellowish soil of Lalmai hill. Other plants are – Neem, Bororia, Harin Hara, Amalaki, Chakshu, Datan, Dhamin, Kurchi, Arok, Shewra, Moyna Kanta, Plum etc.

Mixed (Semi-evergreen) forest types –

The forests of Chittagong, Khagrachari, Rangamati, Bandarban, Cox’s Bazar, Teknaf, Sylhet, Habigonj and Moulavi Bazar are of this type. The forest type is encircled with hillocks of different sizes ranging from 150 to 450 meters. Those forests can be called hilly forests. The soil is almost dark due to the presence of sufficient humus in it. Half of the total forests in the country is of this type. The climate is moist and temperate. The temperature is less than the northern districts like – Rajshahi, Nababgonj, Rangpur, Dinajpur etc. The annual rainfall varies from 200 cm. to 250 cm. This forest type can be divided into two major types, like –

Chittagong-Cox’s Bazar forest types – It covers a large area of Chittagong, Khagrachari, Rangamati, Banderban, Cox’s Bazar and Teknaf, south-eastern districts and is the main forest area of Bangladesh. It extends from Shilchari on the north to Teknaf on the south. The climate is moist and the soil is loamy. Though the forest is a mixed or semi-evergreen type, but can be divided into five categories depending upon their nature.

Evergreen Forest – On the moist hilly plains this forest grows with multiple canopies. Plants inhabiting here are – Garjan (Dipterocarpus turbinatus), Chapalish (Artocarpus chaplasha), Chatim (Alstonia scholaris), Civit (Swintonia floribunda), Ashoka (Saraca indica), Nageswar (Mesua ferria), Buddha Coconut, Telshur, Balshura, Shingra, Long berry etc.
Deciduous Forest – It is found in the in the open hilly slopes and usually contains only one canopy, though there are short deciduous plants found in many places, the plants found here are – Shegun (Tectona grandis), Kanchan (Bauhinia malabarica), Koroi, Chatgaon Pitraj, Bon Sonalu, Ram Tejpata, Tila Garjan, Dhuli Garjan, Uri Jaam, Kanak Champa, Kanta Batna etc.
Bamboo Colony – Different bamboo colonies are found in the Chittagong-Cox’s Bazar forest area, like – Barak bamboo, Talla bamboo, Parua bamboo, Rupa bamboo, Muli bamboo, Balku bamboo, Climber bamboo, Batna bamboo, Hill bamboo etc.
Savannah – Some of the hillocks are barren from trees, but a huge number of herbaceous plants grow there, like – Ulu Hay (Imperata cylindrica), Kash (Saccharum spontaneum) etc.
Sand dune Forest – It is a xerophytic forest developed along the sandy beach; a few plants are found in it, like – Bilati Jhau (Casuarina equisetifolia), Jhau (C. littorea), Ban Jhau (Tamarix gallica), Chagal Kuri etc.

Sylhet forest types – It is situated at the north-eastern corner of the country. Its climate is moist and annual rainfall is about 400 cm. This hillock based forest can also be classified into a number of categories like the Chttagon-Cox’s Bazar forest type.

Evergreen Forest – This forest develops in the hilly plains and contains plants like – Shatim (Alstonia scholaris), Ager plant (Aquilaria agallocha), Garjan (Dipterocarpus turbiatus), Dev Kanchan, Singra, Dhaki Jam, Khoipata, Nageswar, Champaka, Lotka, Forest berry etc.
Deciduous Forest – On the dry slopes of hillocks the deciduous plants grow in profuse number, like – Teak, Shegun, Koroi, Kadamba, Borun, Black Nuja, Tamal, Jarul, Karamja, Pani Jam, Mehgani, Loha wood, Shimul, Pithali, Bhatkur, Chapalish, Kumbhi leaf, Madar, Gamari, Kurchi, Haritaki, Gohra etc.
Bamboo Colony – Scattered throughout the jungles of Sylhet are found bamboo colonies with various types of bamboos and canes, like – Straight Cane (Calamus erectus), Soft Cane, Hill bamboo, Talla bamboo, Muli bamboo, Rupai etc.
Savannah – On the hilly slopes, low lying regions and Haor areas are covered with huge number of grass-like vegetation, like – Ulu Hay, Kash, Nol Khagra, Ikra grass etc.
wampy Forest – A few plants grow in the low lying Haor areas of Sylhet and Sunamgonj, like – Shital Pati (Clinogyne dichotoma), Shyam, Narkula, Baranda, Tarai and Arum.

Biodiversity in a Mixed (Semi-evergreen) Forest type – The eco-system of hilly forest area is the main habitat of wild animals. Asian Elephants are seen in some forests here. In a survey on Chittagong and Chittagong Hill Tract reveales that there are 11 species of Amphibians, 78 species of Reptiles, 382 species of Birds and 129 species of Fishes in them.
In the forest area of Sylhet, especially Vanugach forest near Sreemangal is very enriched in and is inhabited by more than 80% terrestrial wildlife of the country. Slow Lorises, Rhesus monkeys, Stumped tailed monkeys, Hanumans, Langoors, Hoolocks, Black Bears, Barking Deer, Binturongs, Cevets, Fish Cats, Wild Cats, Wild Boars, Rabbits,Squerrels, Shrews etc. are the main terrestrial Mammals found along with 360 species of Birds. The noteworthy ones are – Black Partidge, Wood Peacock, Jungle Fowl, Hill Myna, Spotted Woodpecker, Black Bulbul, Ashy Hornbill, Spotted Swallow, Irrawardi Squirrel, Ashy Squirrel etc. The remarkable reptiles and amphibians are – Bull Frog, Hyla, Hill Tortoise, Deera Turtle, Gekko, Python, Reticulate Python, Common Vine Snake, Common Keel back, Black Krait and Cobra etc.

Evergreen forest types –

A pure evergreen forest is nowhere seen along the terrestrial plains or hilly vallys in the country, but are found as patches of mixed vegetation with the forest types of Sylhet and Chittagong-Cox’s Bazar; the description and list of plants of which are mentioned earlier.

Padma-Meghna alluvial plains –

Most of the landmass in Bangladesh are the alluvial plains of the rivers – Padma, Meghna and Jamuma, except its eastern and northern margins, which are fortified with mountaneous ranges, hills and hillocks. The large plain land in the country is formed from the deposited silt of this riverine country. The plain landmass is again intercepted by an uncountable number of rivers, tributeries, canals, marshes, muddy swamps, blind rivulets, tanks and ponds. Among those exists the peddy lands, jute lands, other crop and vegetable lands as well as some unused patchy forests. Hither and thither around the residing houses, roads and railroads are scattered vegetations of fruit trees, vegetable cultures, sheddy wild plants and scrab jungles. The water bodies are enriched with various types of aquatic plants.

Among the terrestrial plants, the important ones are – Date, Coconut, Palm, Battle nut, Tamarind, Fig, Cane, Plum, Guava, Mango, Wood Apple, Spine Apple, Arum, Akanda etc.

Among the aquatic plants, the important ones are – Water Hyacinth, Water Lily, Lotus, Hydrilla, Leaf Moss, Jhanjhi, Khudi pana, Topa pana, Guri pana, Kuchi pana, Paniphal etc.; with a huge amount of grasses and herbs along the water margins.

Tidal / Mangrove / Coastal forest types –

The tidal forest developed along the tropical coastal zone in the muddy and saline environment, is termed as Mangrove / tidal / coastal forest. The word ‘mangroves‘ is derived from the word ‘helophilous halophytes‘, which means an – ‘Amphibious Saline Plant’. Despite of climatic variations at different parts of the world, the vegetative formation and adaptation of plants in the saline coastal tidal zones are more or less the same.

The Sundarbans

The Sundarban is the largest undivided (formed in a sigle block) tidal /coastal / mangrove forest in the world, situated in the south-west margin of Bangladesh, the largest delta of the world. The forest is about 5,000 years old and is about 5,770 sq.km. (app. 62%) falls within Bangladesh and the rest of it in the West Bengal of India. It itself is 51% of the total forest land in the country. There are more or less 400 rivers and rivulets that intercept the forest landmass. The part of Sundarban within Bangladesh area extend from the Harindanga-Raymangal-Kalindi rivers in the west along the Indo-Bangladesh border, to the Baleswar river in the east and to the southen limits of Satkhira, Khulna, Bagerhat, Borguna and Potuakhali districts. The takes its name from its mainly growing plant Sundari (Heritiera fomes), as is called locally.

The Sundarbans is a naturally protected forest in the country, which is formed in the washed basins of silty and salty delta of the rivers, Padma and Meghna. At some places from north to south it extends about 100km., it is about 270km. from Hatiabhanga of Satkhira at the west to the Burishwar river of Potuakhali at the east. The annual precipitation rate extends from 160-200cm. and the total forest area is swapt over by tidal bores twice in 24 hours, as a result the forest floor is always moist and muddy. But, water is scarce to the plants due to salinity, the situation is termed as Physiologically dry environment, a very distinctive characteristic of mangrove vegetation.

The adaptive characteristics of Flora of Sundarbans

The Flora of Sundarban has its unique adaptive characteristics due to its special environmental condition; like –

Plants of the tidal zone exhibit viviparous germination to avoid floating away along with the down tide every 12 hours. In this case the seeds are germinated while the fruit is attached to the plant and grow to a certain limit to develop root and stem as well as attain a definite weight, that helps their attachment to ground during a down tide. As soon as the due to the daily down tide the water is gradually ebbed away the seedlings start to drop from the plants and very quickly grow roots to attach to the muddy substratum. During the next uptide the attached saplings remain submerged till the next ebbing. During the next down tide a few of the less attached saplings are washed away and rest of them remain and start growing faster to attain a sustainable condition.
The next remarkable characteristic is the formation of breeding roots with respiratory pores, the Pneumatophores. As the tidal water is saline, the amount of oxygen is insufficient that hampers the plant to breeth; it is termed as Physiologically dry situation. So, the plants adapt to it producing vertical pointed roots with a lot of pores in them, which attain a hight that exceeds the normal range of tidal water. As a result the roots can get free air above the water level and can breethe accordingly.
The develop stout stilt roots to remain in an upright condition in such a muddy situation, which not only keep them erect but also help the sand and mud comming along with the uptide to sattle at the plant base increasing the landmass of the mangrove forest. As a result the forest gradually extend to the coastal line and increase the landmass of the country.
Most of the plants have very green, coarse and evergreen leaves that avoid a seasonal shedding off.
The surface of the leaves is covered with heavy cuticle or fibrous outgrowths.
The leaves also have sunken stomata to avoid dehyration and protect physiological draught.
The amount of pallisade parenchyma is much more in the mesophyll tissue to increase the amount of glucose through photosynthesis.
The growth of plants are limited, hence they attain a dome shaped structure.

Biodiverstiy of Flora of Sundarban

There are 334 flowering plants in Sundarban out of 75 plant families. Besides, there are 17 types of Ferns. Bamboos can not grow in Sundarbans due to salinity; similarly plants under families Lemnaceae and Nymphaeaceae also can not grow here. The main plant is Sundari, from which the forest got its name. So, the important plants are – Sundari (Heritiera fomes), Sundari (Heritiera littoralis), Alkushi (Mucuna gigantea), Amur (Amoora cucullata), Garan (Ceriops roxburghii), Bain/Bina (Avicennia officinalis), Bhola (Hibiscus tiliaceus), Dhundul (Carapa obovata), Fern (Acrostichum oureum), Gewa (Excoecaria agallocha), Golpata (Nipa fruticans), Hargoja (Acanthus illicifolius), Hintal (Phoenix paludosa), Kankra (Bruguiera gymnorhiza), Kewra (Sonneretia apetala), Keya (Pandanus sp.), Khalshi (Aegicras rotundifolia), Khapu (Rhizophora conjugata), Kulshi (Aegiceras majus),Poshur (Carapa moluccensis), Shingra (Cynometra remiflora), etc.

Mangrove Fauna of Sundarban

There are 32 – 57 types of mammals in Sundarbans, of which the world famous Royal Bengal Tiger (Panthera tigris bengalensis) is present; the total number of specimens are about 200 today (according to a study report, 2005). Other mammals are – Spotted deer (Axis axis), Barking deer (Muntiacus muntjak), Rhesus monkey (Macaca mulatta), Wild boar (Sus scrofa), Hoary bellied Himalayan squirrel (Callosciurus pygerythus) etc. Previous records reveal that there were – Swamp deer (Cervus duvauceli), Sambar (Cervus unicolor), Wild bufallow (Bubalus bubalis) and Javan Rhinoceros (Rhinoceros saudaicus) in this forest, but today they are totally extinct.

Recent reports show that there are 286 – 315 species of birds in Sundarban, the common ones are – Indian Pond heron (Ardeola grayii), Cattle egret (Bubulcus ibis), Eurasian Spoonbill (Platalea leucorodia), Greater Adjutant stork (Leptoptilos dubius), Pariah kite (Milvus migrans govinda), Brahminy kite (Haliastur indus), Common Kingfisher (Alcedo atthis), White breasted Kingfisher (Halcyon smyrnensis), Indian Koel (Cuculus micropterus), Magpie robin (Copsychus saularis), different Doves and Woodpeckers etc. Earlier Indian Grey Jungle fowl (Gallus sonneratii) was found here, but now totally extinct.

Among the reptiles, the Estuarine Crocodile (Crocodylus porosus),Bengal monitor lizard (Varanus bengalensis), Rock Python (Python molurus), King Cobra (Ophiophagus hannah), Green Turtle (Chelonia mydas) etc. are very common and world famous. The Fresh Water Crocodile (Crocodylus palustris) was found earlier, but they are totally extinct from here.

There are 8 species of Amphibians identified so far from here, like – Green frog (Euphlyctis hexadactylus), Tree frog (Polypedates maculatus) and others.

Due to its unparallel beauty, peculiarity and sefl-sustainability as well as its diversified faunal resource, the three parts of Sundarban (in total 1400 sq.km., 24% of the total area) has been declared as World Heitage Site by the UNESCO in 1997; those are –

The East Wildlife Sanctuary, under Swarankhola Forest Range (54 sq.km),
The South Wildlife Sanctuary, under Khulna Forest Range (179 sq.km) and
The West Wildlife Sanctuary, under Satkhira Forest Range (90 sq.km).

Coastal / Tidal Forests and Green Belt

Beside the natural forest resources, special type of artificial forests have been formed recently in small patches along the coastal margin within the tidal zone. This type of special forest developed with suitable and sustainable plants along the shoreline for a special purpose is termed as the Green Belt. It can again be of two types –

Sea Beach Vegetation / Green Belt – They are artificial forests created with non-mangrove vegetations in the sandy isolated islands raised in between the shore and the sea, in the southern districts of – Cox’s Bazar, Chittagong, Noakhali, Bhola, Potuakhali and Barguna. The suitable plants in these vegetations are – Jhaw, Kathbadam, Coconut, Palm, Date, Battle nut, Palita Mandar, Pania Mandar, Punial, Porash, Karamja, Hijal, Nishinda, Shisho etc.
Coastal Vegetation / Green Belt – They are artificial forests developed with mangrove vegetations for the tidal zone and non-mangrove vegetation for the high lands beyond the reach of tidal water. This program has been underway since 1976 in Bangladesh in our coastal sandy islands of greater Noakhali, Chittagong, Barisal, Potuakhali etc. districts, where Dharshi type of grasses grow and the coastal margin is swapt daily with tidal water. These forests are the primary stages of plant succession and are formed with all mangrove type of plants except Sundari and Garan. About 90% of these vegetations constitute with Kewra; other mangrove plants are – Bain, Gewa, Golpata, Kankra, Karamja etc. The high lands in these forests where the tidal water does not reach are formed with non-mangrove vegetations like – Garjan, Raintree, Babla, Koroi, Epil-epil etc.

Necessity of creation of Coasta Vegetation / Green Belt

Natural calamities like – Cedor, Ayla, Nargis, Mahasen etc. has been a regular event in our country along with tidal bores or surges. According to the map the Bay of Bengal has squezed like a funnel and has entered the southern belt of our country. So, when a depression formes in the Bay of Bengal, it is found to move to our main land through that funnel-like route, increase in power and hit the coastal areas. We have no other powerful alternative to protect or defend us from such environmental disasters but a green belt or coastal forest along our coastal margin of southern districts. Therefore, the endaevour of forming a strong green belt in our southern margin has been underway since 1976.

Besides, the drastic increase in our population size and alarming trend of deforestation have been pushing us toward the decrease of Oxygen and increase of Carbo-di-oxide content in our enviroment along with a constant raise of temperature – a way to Green house effect. So, to defend us from all those natural deformities a Green Belt is very essential. It can not only protect us from atmoshpheric imbalance but also from the huge amount of soil erosion from a tidal bore or surge, occuring during any natural calamity. The plants decreases the velocity of air during such troubles and protects the coastal soil from erosion with strong anchorage of their roots. Moreover, people can use fruits (Coconut, dates, battle nuts etc.), leaves (Hogla, Golpata etc.), plant products (wood, fibre, firewood etc.) of those vegetations – a way toward economic solvancy of our down trodden and less fortunate people.

it is noteworthy, a country should have forest area at least 25% of its total landmass. We have only 8% of our total area left for vegetation. So, the program of green belt formation is also a step ahead towards our recovary of that loss.

Our Threatened Biodiversity

Biodiversity

The word Biodiversity is an abbreviated form of the term Biological Diversity, first coined by Walter G. Rosen (USA) in 1985. Biodiversity means the diversified organisms inhabiting the present world with their varied characteristics, habits, habitats and adaptive radiations (capability to adapt over a long period of time with gradual characteristic changes but retaining the main ones). A justified definition for the term Biodiversity was defined in the Earth Summit (June 03-14,1992) at Reo-De-Generio, Brazil in the Convention on Biological Diversity (CBD). It postulates that – “Biodiversity means the variability among living organisms from all sources including, inter-alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which thay are part – this includes diversity among species, between species and of ecosystem”.

It is obvious that, there has been variation community to community, population to population, species to species and even specimen to specimen within a species in a given eco-system or a biome. So, the simulated study of all those eco-types and their inhabiting individuals and their behaviours as well as the intra-population and inter-population interactions have been included in the study of Biodiversity.

Threatened Species and IUCN Category

IUCN (International Union for the Conservation of Nature and Natural Resources), an international organization, monitoring globally the sustainability of Species, has published recently a Red Data Book of Vascular plants and a Red List of threatened aminals of Bangladesh. As the possibility of survival for certain species has been vulnerable and their population has gone dwindling at different habitats and locations round the globe, due to the scarcity of food and adequate shelter, the census, assessment and analysis of such organisms and publishing their scientific data is as essential as their survibal. The Red Data not only alerms us about the vulnerability of a species but also the scientific causes behind its present threatened condition. So, based on the list, substatial measures can be taken to save a threatened species from its ensuing extinction. According to the Red Data Book the Threatened Species are divided into following categories –

Extinct Species – When the last specimen of a given Species has undoubtedly died in a given area or the total world, it is declared as Extinct. e.g., the 3 species of Rhinoceros and the wild buffalo has been extinct from Bangladesh.
Critically Endangered Species – When there is a risk of extermination of more than 50% of all specimens of a given Species in a given area within the next 10 years or within the next 3 generations, it is declared as Critically Endangered. e.g., The Royal Bengal Tiger and the Shar Puti fish are the Critically Endangered species of BD.
Endangered Species – When a Species is not critically endangered but, there is rist of its extermination of 20% of all specimens within the next 20 years or within its next 5 generations, it is termed as Endangered. e.g., The Rhesus Macaque and the Chital Fish are endangered in BD.
Vulnerable Species – When a Species is neither critically endangered nor endangered but, there is a rist of its extermination of 10% of all specimens within the next 100 years, it is termed as Vulnerable. e.g., The Monitor Lizard and the Red Fox has been vulnerable in BD.

Biodiversity Crisis

Biologists have discovered so far 1.75 million of animal Species and 270,000 vascular plant Species. A census conducted by 16 organization over 20 years reveal that within the 270,000 vascular plant species, 34,000 (12.5% app.) are under risk. According to Edward O. Wilson, an Evolutionary Biologist of Harvard University, USA, about 27,000 species per year, 74 species per day and 3 species per minute are becoming extinct in the world and the 20% of the present species could be extinct with 2020. Most of the scientists support Wilson, as this sort of abnormal extinction had occured five times in the world history (for the Ordovician to Cretaceus periods). The catestrophic physical disasters like – environmental change or meteorite impact etc. had caused mass extinction in the eco-systems all around the globe.
During the 5th such mass extinction in the Cretaceus period 76% of organisms including the Dianosaurs were exterminated instantly due to a meteorite impact. In the same way about 18 species of animals have been extinct from Bangladesh within the last century, like – One horned Rhinoceros (Rhinoceros unicornis), Javan Rhinoceros (R. sondaicus), Two horned Rhinoceros (Didermoceros sumatrensis), Gour/Bon Goru (Bos gourus), Bunteng/Mithang (B. banteng), Wild buffalo (Bubalus bubalis), Blue Bull/Neel Gai (Bucephalus tragocamelus), Samber/Bara Singa Harin (Cervus duvauceli), Hog deer/Para Harin (Axis porcinus), Leopard (Canis lupus), Pink headed duck (Rhodonessa caryophyllacea), Peacock (Pavo cristatus), Muggar/Fresh water Crocodile (Crocodylus palustris) etc.

Significance of Biodiversity Conservation

Though we do not know all the important reasons of Biodiversity conservation, yet some of those are as follows –

Ethical reasons – The cultural heritage, religious belives, political ideology etc. are all formed from natural systems. Each and every individual in nature has its right to survive and so it is the formost duty of humans to conserve the biodiversity and have no rights to destroy it. Besides, the relationship and bondage with nature brings benefits to human beings.
Aesthetic reasons – The beauty of nature attacts us and to maintain it, a number of organizations have been working for biodiversity conservation and development. The love for nature has a direct influence on the industrial, cultural and literary life of a nation. It is believed that, the relation of human being to nature brings immense pleasure and benefit.
Utilitarian reasons – The biodiversity and wildlife has been directly related to human basic requirements since the time immemorial. For example, agriculture, forest resource, fish culture, poultry, bee culture, housing, clothing, medicine etc. are directly related to our day to day life, while insects and birds help in pollination and pest control and thus help our survival indirectly. In this way we are directly or indirectly dependant upon our environment and biodiversity, from the micro-organismal level to the largest organism present in it. People in the world use about 40,000 species of plants and animals daily for their survival and 40% of the active ingradients used for medicine preparation in the USA are organic products.
Ecological reasons – Besides the direct influence of biodiversity the total welfare of humans depends upon a complete and functional eco-system i.e., on a Biosphere. A justified eco-system is inavitable for the survival and sustainability of a Species and a balanced bio-chemical cycle is essential for it. It is also important for a climatic balance, which along with deforestation, reclamation, siltation and precipitation etc. are directly related to and affected by biodiversity. For instance, the green plants control the amount of CO₂ in the air and also produce O₂ as a byproduct of Photosynthesis as well as have direct impacts on rainfall and erosion. The eco-system is directly affected by the eradication of any Species from it and so, the conservation of a sustainable biodiversity is inevitable for the existance of mankind.

Causes of Biodiversity Loss

Biodiversity is shrinking day by day and this is a global crisis. According to Edward O Wilson, we are loosing 3 species every minute. It is really tough to identify the real cause of biodiversity destruction, but a few of the main ones can easily be identified, like –

Human population explosion – The main reason behind the biodiversity loss is the population expansion. Today some 700 crore people inhabit the earth which is believed to be going to become 1200 crore by 2050. The existing human population is using about 50% of the organic products like – food material, useful products, medicines etc. of the present world. As a result to meet such a huge amount of organic requirement the biodiversity in the whole world is gradually dwindling and reducing.
Destruction of natural habitats by humans – Since the advent of agriculture 10,000 years ago, the humans has increased from 50 Lac to 700 crore today. In the mean time, revolutionary changes has occured on earth due to human endeavour to meet their basic and other requirements. The human beings occupied the forests, grass-lands, wet-lands and many natural habitats for growing crops and other plantations or building dams, roads and railways for making their communication easy. But, unfortunately they destroys a lot of eco-systems, the habitat of innumerable organisms who had survived earlier. So, as a result of habitat loss a considerable amount of biodiversity has been lost.
Over exploitation of natural resources – Biodiversity is directly destroyed or hampered due to the over exploitation of our natural resources like – fish, bird, land and sea. For instance, among the 13 largest marine fisheries, 12 has become fishless. Due to modern fishing techniques like – large fishing nets, bottom vacuuming etc. aquatic invertebrates and other non-profitable fish populations are drastically hampered. The extinction of Passanger Pegion from the South America is one of the most important example of over-exploitation; the last specimen died in 1914. In the same way, the Penguine-like Great Auk, Zebra-like Quagga, Ostrich-like Moa and the tawny horse Tarpan have been extinct.
Bio-invension – Due to population explosion in the world today humans are expanding to the nook and corner and interfaring in many food chains directly related to biodiversity of that area. As a result of struggle for basic needs like food and shelter, usually the humans succeeds and some of the organisms lose their existance. Besides, due to human interference many animals and plants are introduced to many places, which struggle for their existance with their local competents. In this way the biodiversity has been interfered and in some cases destroyed. The invension of a new organism to a new place has a direct impact on any of the trophic levels of the existing food chains. The flightless bird Dodo became extinct due to the introduction of Dogs and Swins in Morishus islands by the Dutch sailors. Likewise, 6 native birds became extinct due to the introduction of Brown Tree Snake in Guam island by the accedental invasion of a military cargo ship during World War II.
Environmental Pollution – It is one of the most important factors that destroy biodiversity. The exhausts from veheicles, Factory and Radioactive wastes, unscientific use of insecticides, pesticides, chemical fertilizers etc., oil spelt from wrecked tankers and oil refinery wastes, when liberated in nature created unwanted hazards for the normal life style and bio-clycles. This is known as environmental pollution and it may be the air, water, soil which can be polluted and hamper the eco-sytems as well as affect the biodiversity; besides, there can be noise, light and odour pollusions, which hamper the normal life of humans.
Natural Calamity – It is one of the major factors of habibtat destruction or disruption. Natural calamities like – Earth quakes, Harricanes, Psunami, Cyclones, Tornadoes, Draughts, Innundation, Tidal bores and Surges, Flood, Forest fire, Land slides and ice slides etc. destroys natural situations and disrupts normalcy of a natural habitat. It needs a long time to recover such losses or in cases it is never recovered.
Glorbal Warming – Among the Green House Gases, CO₂ is the main one. More than 70% of this gas has been produced by the developed countries in their factories as well as power plants. As a result, the temperature of the whole world is increasing, termed as Global warming. It has a direct impact on melting of ice in the mountains and polar regions, as well as in the raise of water level globally that will submerge at least 30% of the present low lying regions. Scientists are of the openion that, with 2050 the global temperature will increase by minimum 1.5^oC and maximum 5^oC. As a result, many of the existing organisms will lose their habitat and become extinct. In Bangladesh at least 3 million Hectres of land is supposed to be submerged through this impact.
Wildlife exploitation – Many rare animals are trapped and killed for their bones, blood and hide, like Tigers, Deer, Wolves and Bears. Some very costly Fur Coats are prepared and people use other parts for luxurious purpose. In some part of the world like Indo-China, tiger and snake blood is taken as a helath drink. Besides, a huge number of wild animals have been used for research purpose, what has in some places made many Species endangered.

Biodiversity – Bangladesh Perspective

Due to unique geographical location the biodiversity of Bangladesh is very enriched. Positioned southern to the foothills of Himalayas, the country is influenced by monsoon air and is a drainage zone intercepted by a huge number of rivers and their tributeries. Bangladesh posses a lot of natural facilities and has become a centre of biodiversity as an integral part of the Indus-Ganges alluvial plains. The total area of the country is 148,393 sq.km. and the population density is 880 per sq.km. It is fortified with 5000 species of plants, 282 sp. of Protozoans and 4109 sp. of Invertebrates. There are 895 species of endamic and resident animals (266 sp.of Fishes, 22 sp. of Amphibians, 109 sp. of Reptiles, 388 sp. of Birds, 110 sp. of Mammals), while there are another 702 species of marine and migratory vertebrates (442 sp. of Marine Fishes, 17 sp. of Marine Reptiles, 240 sp. of Migratory Birds, 3 sp. of Marine Mammals).

The resource of biodiversity in Bangladesh is undoubtedly surprising. Once existed the dense forests of Chittagong, Chittagong Hill Tracts, Sylhet, Dhaka, Tangail, Mymensingh, Rangpur and Sundarbans has enriched the country so much that the existing biodiversity and species count is still praiseworthy. The huge wetland areas in the central and southern regions has made it more important in respect of biodiversity. It is noteworthy, being 1/20th of India in area, it contains 629 sp. of animals, while India contains 1500 sp. Again, France is four times bigger than Bangladesh, which contains 375 sp. of wildlife, while we have 895 sp. In entire Europe there are 374 sp. of fresh water fishes, while we have 266sp.

Of the total 895 species of resident vertebrates, 201 sp. are threatened. Of those, 64 sp. are Critically endangered (12sp. of Fishes, 12sp. of Reptiles, 19 sp. of Birds, 21 sp. of Mammals); 86 sp. are Threatened (28 sp. of Fishes, 3 sp. of Amphibians, 24 sp. of Reptiles, 18 sp. of Birds, 13 sp. of Mammals); and 51 sp. are Vulnerable (14 sp. of Fishes, 5 sp.of Amphibians, 22 sp. of Reptiles, 4 sp.of Birds, 6 sp. of Mammals). So, expets are of the openion that, conservation measures should be taken as early as possible, to save the threatened organisms of the country from their upcomming extinction.

According to the report of IUCN (International Union for Conservation of Nature and Natural Resources), published in 2000, there are 62 Critically Endangered animals in Bangladesh; a few of which are given below –

Some Critially Endangered Animals of Bangladesh :

Bengali name	English name	Scientific name	Class
Shar Puti / Sharna Puti	Olive Barb	Puntius sarana	Actinopterygii
Pangash	Pungas	Pangasius pangasius	Actinopterygii
Lona Joler Kumir	Estuarine Crocodile	Crocodylus porosus	Reptilia
Ghorial / Mecho Kumir	Gavial / Gangetic Gharial	Gavialis gangeticus	Reptilia
Raj Shokun	King Vulture	Sarcogyps calvus	Aves
Chandana / Bara Tia	Large Indian Parakeet	Psittacula eupatria	Aves
Lajjaboti Banar	Slow Loris	Nycticebus caucang	Mammalia
Bagh	Royal Bengal Tiger	Panthera tigris	Mammalia
Shushuk / Shishu Mach	Gangetic Dolphin	Platenista gangetica	Mammalia

Conservation of Threatened Species

Threatened plant species of Bangladesh

Bangladesh National Herbarium has published the ‘Red Data Book of Vascular Plants of Bangladesh’ in 2001, with a list of 106 threatened plants species of the country. A few of them are given below –

Bengali name – Bonno Tal / Tali Palm /Tara Tal
English name – Tali Palm / Ghost Palmera Tree
Scientific name – Carypha taliera Roxb. (Fam. – Arecaceae)
(Discovered in 1819 in Bengal by Sir W. Roxburgh and at Dhaka Univ. campus in1950, the only specimen in BD last flowered in 2010 and died afterwards. Mr. Akhteruzzaman, a Ph.D. fellow of DU, Dept.of Phermacy under Prof. Dr. Abdur Rashid, collected seeds and developed 2000 saplings out of them which they have been distributing all over the country with the help of govt. authorities. They planted sapling at all govt. establishments and eminent colleges like Notre Dame College in 2010. The rare plant blooms only once in 100 years and dies after that)
Bengali name – Malacca Jhanji
English name – Malacca Jhanji
Scientific name – Aldrovanda vesiculosa Linn. (Fam. – Droderaceae)
(an endangered plant found in Chalan Beel, Rajshahi, and later found in 1974 at Dharasher Beel, Putia UZ., Rajshahi)
Bengali name – Khude Barala
English name – Lesser Barala
Scientific name – Knema bengalensis de Wilde (Fam. – Myristicaceae)
(a vulnerable plant, endemic in BD, found in Dulhazra, Cox’s Bazar)
Bengali name – Korud
English name – Korud
Scientific name – Lictuala peltata Roxb. (Fam. – Palmae)
(a vulnerable plant found in Chittagong, Rangamati and Sylhet)
Bengali name – Rotella
English name – Rotella
Scientific name – Rotela simpliciuscula Kuhne (Fam. – Lathraceae)

Threatened animal species of Bangladesh

Bengali name – Gharial / Mecho Kumir
English name – Gavial / Gharial
Scientific name – Gavialis gangeticus
Bengali name – Jalar Kumir / Mitha Jaler Kumir
English name – Mugger / Marsh Crocodile
Scientific name – Crocodylus palustris
Bengali name – Raj Shokun / Lal Matha Shokun
English name – King Vulture / Red Headed Vulture
Scientific name – Sarcogyps calvus
Bengali name – Neel Gai
English name – Nil Gai / Blue Bull
Scientific name – Bucephalus tragocamelus
Bengali name – Shushuk / Shishu Mach
English name – Gangetic Dolphin / Fresh Water Dolphin
Scientific name – Platanista gangetica

Conservation measures of Biodiversity

The simulated effort to protect the destruction and extinction of biotic communities is known a Biodiversity Conservation. Since the eve of civilization the human community have been destroying the natural environment and biodiversity for their amnities and shelter, and have subjected those to a threatened condition today. So, to escape the ensuing disaster the following measures are to be taken –

Growing Consciousness through Education – To educate people formally at all levels in the existing educational institutions about biodiversity and its proper conservation to build up a conscious generation in this concern.
Growing Public Awareness – To educate people of all walks of life informally, through programs and mass media, like – Radio, TV, Newspapers, Magazines etc. about the relationship of biodiversity and environment, the causes and adverse effects of biotic community destruction, and the human role in the cause and remedies of such problems.
Lagislation for Biodiversity conservation and their implementation – Creating lagislative acts for the protection and conservation of biodiversity and wildlife, and their proper implementation.
Habitat conservation, extention and development of organisms – The best habitat of organisms is the forest; so, the destruction of forest must be stopped like deforestation and cutting down of hills, to maintain a congenial environment preserving forest areas and at the same time reforresting and extending them.
Protection of environmental pollution – One of the main cause of biodiversity destruction is environmental pollution. The emission of poisonous gases out of factories and veheicles, expulsion of chemical wastes of industries and the use of excessive insecticides and pesticides in crop fields have been the main causes of biodiversity destruction; the preventive or protective measures of which must be taken.
Establishing National parks, Game reserves, Sanctuaries and Protected areas – These programs fall under In-situ biodiversity conservation and practiced to conserve the organisms in their own habitat or artificial ones.
Habitat Management – This includes the collection and research on the habits, habitats and behaviour of wildlife and their proper management in their natural habitats. The proper management is not possible without requisite knowledge and their proper application according to the changeable situations.
Stopping the endangered animal trade / trafficking – A strong step should be taken through national and international authorities to stop wildlife trade and trafficking, especially the endangered ones. This is one of the most important factors of habitat destruction and species extermination.
In-Situ and Ex-Situ Conservation of Biodiversity – Conservation of forest and wildlife or any organism keeping it within its natural habitat is termed as In-situ conservation, while keeping it in specialized scientific locations outside its natural habitat is termed as Ex-situ conservation. Both are very essential today for the sustainability of present organisms and to avoid the extinction or extermination of a species. The in-situ conservation includes the establishment of – Botanical gardens, National parks, Sanctuaries, Game reserves, Wetland management etc., while the ex-situ conservation includes the establishment of – Seed bank, Pollen bank, Clone bank, Tissue culture bank, DNA bank, Zoo (with captive breeding programs), Safari park, Eco park etc. Through the in-situ program the organism is left to survive in its own habitat in a natural environment, while through the ex-situ program the organism or its parts are preserved for its survival and culture in nature to avoid its extermination as well as retain its original characteristics.

In-situ Conservation of Biodiversity

The process of conservation of an organism keeping it inside its own eco-system or its macro- or micro-habitat to retain its diversity, is termed as In-situ conservation of Biodiversity. This program can be done in Bangladesh in the following ways –

Botanical Gardens – Botanical gardens with varied type of common and rare plantations can be established at different public going places in the country and left open for observation of plants and animals as well as for recreation. For instance, Botanical garden (Mirpur-1, Dhaka), Baladha garden (Wari, Dhaka) etc.
National Parks – National parks can be created at suitable places under the supervision of the Govt. Forest Department and left open for public for observation of plants and animals as well as recreation, like – The Vawal National Park (Shal forest, Gazipur), Modhupur National Park (Shal forest, Tangail), Himchari and Medha Kachapia National Parks (Hill forest, Cox’s Bazar), Kaptai National Park (Hill forest, Rangamati), Nijhum Island National Park (Coastal forest, Noakhali), Lawachara National Park (Hill forest, Moulavi Bazar), Satchari National Park (Hill forest, Habigonj), Khadim Nagar National Park (Hill forest, Sylhet), Ramsagar National Park (Shal forest, Dinajpur). Those are created to preserve our plant species in natural environment.
Wildlife Sanctuaries – Those are concealed forest areas where public movement and hunting is totally banned to preserve the natural biodiversity and the wildlife. Our sanctuaries under strict guidance of the Govt. Forest Department includes – East, South and West Sundarban (which have been declared in 1997 as 798th World Herritage Sites), Kukri-Mukri Island (Bhola), Publakhali (Chittagong Hill Tract), Chunti (Chittagong), Fashiakhali (Cox’s Bazar) and Rema-Kalenga (Habigonj). Formation of a Deer Park and the Tiger Poject at Sundarban is underway.
Game Reserves – Those are particular areas for the preservation and observation of natural vegetation and wildlife where public movement and hunting is restricted. Those are under supervision of the Govt. Forest Department and are open to public for a limited time and under permission. We have such game reserves, like – Teknaf area (declared in 1983), Dulhazra Shafari Park (Chittagong), Barabkundu Eco Park (Chittagong) and Madhabkundu Eco Park (Moulavi Bazar).
Fish Sanctuaries – Different fish species in natural habit has been dwindling since recent time in Bangladesh due to fish culture in those places. As a result, the spawning grounds of the natural population of fishes have been squeezed to only a few pockets. So, the only way to keep them viable and diversified is the creation of certain fish sanctuaries where they find all facilities for their normal food, spawning and habitat. A few drives in this concern have been taken in our country, like – The Halda river (Chittagong) has been declared as a Fish Sanctuary, where catching of fish and liberating harmful chemicals are totally banned. Carps (Rui and Katal) present in that water liberate eggs during the rainy season, which are collected and formed into fries in the laboratories and distributed over the country to increase their population as well as economic gain. Similarly, the Jamuna river at Bahadurabad Ghat, Jamalpur and the Padma river at Aricha Ghat, Dhaka can be declared as Fish Sanctuaries to preserve the natural wealth of fishes.
Conservation of Haor / Wetland areas – The resourceful wetlands around the globe are now conserved according to RAMSAR convention (1971) on Wetland Management, held at Ramsar, Iran. 1550 sites around the globe which were once very resourceful wetlands have been identified and conserved since 1975 according to the decisions made out in the convention; those are known as Ramsar Wetland sites. The Hail Haor, Hakaluki Haor and Tanguar Haor under the greater district of Sylhet come under those sites, which were once very resourceful in biodiversity. These places in our country can still be preserved through proper management to retain and regain their biodiversity for their aquatic plants, fishes and migratory bird resources.

Ex-situ Conservation of Biodiversity

The process of conservation of an organism outside its own eco-system or its macro- or micro-habitat to retain its diversity, is termed as Ex-situ conservation of Biodiversity. This program is applied to rare organisms where their habitats has been disrupted due to natural disaster or human interference. It is also applied to endangered and vulnerable species which are threatened to extinction and itself is a troublesome and costly process. The ex-situ program includes – Seed Bank, Pollen Bank, Clone Bank, Tissue Culture Bank, DNA Bank, Zoo (including captive breeding), Botanical Garden, Safari Parks and Eco Parks etc. Some of Eco Parks in Bangladesh are – Madhabkundu Eco Park (Moulavi Bazar), Shitakunu Botanical Garden and Eco Park (Chittagong), Banshkhali Eco Park (Chittagong), Modhutila Eco Park (Sherpur), Dhanshiri Eco Park (Jhalakathi), Kuakata Eco Park (Potuakhali), Tilagarh Eco Park (Sylhet) and Borshijora Eco Park (Moulavi Bazar).

Preservation under low Temperature

Different seeds, pollens, tissue for tissue culture, Germplasm or DNA etc. can be preserved under low temperature (-10^oC to -20^oC). Seeds or stems used for germination (like Potatoes) or roots (like Sweet Potatoes) can be preserved under suitably low temperature (4^oC to 10^oC) depending upon Species in the Cold storages or Seed Banks / Germplasm collection centres. The largest of its kind is situated in Gazipur district at the Bangladesh Agricultural Institute (BARI), Joydevpur. Besides, Bangladesh Forest Research Institute (BFRI) has established two Clone Banks at Hyako of Chittagong and Ukhia of Cox’s Bazar, where clones of seven timber yielding plants, including Shegun and Garjan are preserved. Moreover, Pollen grains, tissue for Tissue Culture, Bacteria Culture etc. can be preserved under 4^oC. DNA extracts can be preserved in vials under -20^oC, pouring sterilized Clove Oil over it; here the oil works as a Cryoprotenctant.

Preservation under very low Temperature / Lyophilization

Preservation of samples of DNA and Bacteria under very low temperature (-197^oC) is termed as Lyophilization. In this system the DNA or Bacteria samples are preserved in small amples under a temperature as low as -197^oC with the help of Liquid Nitrogen; the device used for this action is known as a Lyophilizer.

Zoogeography (Geographical distribution of animals)

Our world is about 460 crore years old. Though some relics or fossils signifies that they are 100 crore years old, but substantial proofs signifies that the advent of animal life started 60 crore years ago. Since then, a number of animals have evolved and many have been extinct in the continued race of evolution. At present the total number of animal species is about 15 lac.

Animals inhabit everywhere in the land and water of the earth but their distribution is not the same at all places. As the configuration of earth today differs in many respect to that of the primitive condition, the distribution of animals today also vary to that of the past. For instance, the Rhinoceros and Elephants are found today only in Asia and Africa, but fossil findings signify that they were present in Europe and America as well in the past.

The branch of Zoology that deals with the geographical distribution, nature of dispersion, environment and its impact on animals and their habitat, is known as Zoogeography, a unique section of animal study. Though the geographical distribution of all invertebrates and vertebrates are included in this science, but the discussion and study today is confined within the Phylum : Chordata and only on Fishes, Amphibians, Reptiles, Birds and Mammals; all of which have 45 thousand Species identified so far.

Zoogeographical Regions

The total area in the world is divided into a number of regions based on the distribution of animals, which are known as Zoogeographical Regions. Alfred Russell Wallace (1876) divided the world into six zoogeographical regions based upon the distribution of Vertebrates; which are given below in a tabular form –

Zoogeographical Regions	Areas included in the regions
Palaearctic Region	Total Europe, Part of Africa north of Sahara, North part of Himalaya in Asia – Afghanistan, Iran, North China, Japan, North Siberia and Arctic Peninsula.
Oriental Region	Pakistan, India, Sreelanka, Bangladesh, Nepal, Myanmar, Thailand, Singapore, Indo-china, Malaysia, Philippines, Taiwan and Sumatra, Java, Borneo and Bali island of Indonesia.
Australian Region	Australia, Tasmania, Peninsula east to the Wallace’s Line, i.e., Lombok to Timor, Malacca and New Guinea islands, New Zealand and many small islands in the Pacific.
Nearctic Region	North America, Canada, Greenland and the part of Maxico north to the Tropic of Cancer.
Neotropical Region	The total central America but the north part of Maxico, South America and West Indies Peninsula.
Ethiopian Region	The total of Africa including parts of Sahara south to the Tropic of Cancer, Southern Arabia, Madagascar and a few marine islands.

The Oriental Region

Geographical Limits – It includes, Pakistan, India, Sreelanka, Bangladesh, Nepal, Myanmar, Thiland, Singapore, Indo-China, Malaysia, Phillipines, Taiwan (Formosa), and Indonesian Sumatra, Java, Borneo, Bali etc. islands. North to this region is the mighty Himalayas, to the East is the Pacific and to the South is the Indian Ocean. It can be isolated from the Australian region to the South-East through the Wallace’s Line.
Wallace’s Line – Starting from the North and passing through Phillipines and Malaccus, turning to the South-West and passing through Borneo and Sibiles (Solaesae) islands, it ends to the South in between Bali and Lombok islands; it isolates the oriental from the australian region. But, some scientists isolate the oriental from the australian region through a Max Weber’s Line, a little eastward than the Wallace’s Line. The zone existing in between the Wallace’s line and Weber’s line is termed as Wallacea.
Sub-Regions – Alfred Russell Wallace divided the Oriental region into four sub-regions, like –Climatic condition – The oriental is basically a moist dry region. In this area, Phillipines, Malaysia, Singapore, Brunai and Indonesia exhibit tropical climatic condition. Excessive heat and precipitation all over the year is the main cause of such climate. Damp conditon, scorching heat and a humid condition exists in the area due to excessive humidity. The Sun shines perpendicularly over the region all over the year, resulting in excessive heat; and the days and nights are of same duration. The countries within this region are almost placed along the sea and the terrestrial condition is uneven (elevated) plains. Bangladesh, India, Pakistan, Myanmar, Thailand, Indo-china, Southern Japan and Phillipines come under tropical breeze zone. Excessive heat by the Summar and excessive rains as well as dry rainless winters are the specific climatic characters of this region.
- Indian sub-region – This sub-region contains the middle and north of India, extending from the Indus and foothills of Himalayas in the North to Mysore in the South via Goa. This sub-region is again divided into seven smaller regions of which one is the Gangetic Plain; Bangladesh lies in this plain.
- Ceylonese sub-region – Parts of Indian Peninsula; Sreelanka lies in this sub-region.
- Indo-china sub-region – Southern limit of Palaeactic border of China, Myanmar, Thailand, Andamans, Taiwan and Hainan Peninsula falls under this sub-region.
- Indo-malayan sub-region – Malay Peninsula and East Indies Islands (like – Borneo, Java, Sumatra and Andmans and Nocobar Peninsula) fall under this sub-region.
Climatic condition – The oriental is basically a moist dry region. In this area, Phillipines, Malaysia, Singapore, Brunai and Indonesia exhibit tropical climatic condition. Excessive heat and precipitation all over the year is the main cause of such climate. Damp conditon, scorching heat and a humid condition exists in the area due to excessive humidity. The Sun shines perpendicularly over the region all over the year, resulting in excessive heat; and the days and nights are of same duration. The countries within this region are almost placed along the sea and the terrestrial condition is uneven (elevated) plains.
Bangladesh, India, Pakistan, Myanmar, Thailand, Indo-china, Southern Japan and Phillipines come under tropical breeze zone. Excessive heat by the Summar and excessive rains as well as dry rainless winters are the specific climatic characters of this region.
Flora – As a result of excessive heat and rainfall most of the year, deep Evergreen forests have developed in this region, where vines and liana grows along with plants containing large superposed leaves. Forests are dense and the trees grow taller as a result of competition to get the sunshine. The main vegetation of this region are – Teak, Mehgani, Ablush, Rosedew, Rubber, Palm, Bamboo, Cane, Cocoa, Tea, Coconut etc. Along with the tropical Evergreen forests (where the trees shed leaves all over the year; main vegetation are – Teak, Shegun, Mehgani, Willow, Pine, Far, Ablush), Deciduous forests (where the trees shed their leaves in the winter and grow leaves by the Spring; the main vegetation are – Shegun, Arjun, Sundari etc.) are also seen along with scrab jungles and open grass-lands. Besides, there are Bamboos, Cane bushes, Mangos, Jackfruits, Balack Berris, Coconuts, Battle-nuts, Chaps, Rubbers, Jutes, Cottons, Tobaccos, Oil seeds, Coffee and Cynchona etc., which grow porfusely. A very distinctive character of this region is the Mangrove Vegetation growing by the coastal margins, which contains plants like – Sundari (Heritiera fomes), Goran (Ceriops roxburghii), Gewa (Excoecaria agallocha), Poshur (Carapa moluccansis), Kewra (Sonneratia apetala), Bora (Rhizopora conjugata), Hargoza (Acanthus illicifolius), Golpata (Nipa fruticans), Kankra (Bruguiera gymnorhiza), Bina (Avicennia officinalis) etc.
Fauna (Endemic) – The oriental region is enriched with 157 families of vertebrates of which – 23 are of Fresh Water fishes, 9 of amphibians, 29 of reptiles, 66 of birds and 30 of terrestrial mammals; many of which are endemic. When an organism is found only in a particular area in limited number, it is termed as Endemic.
- Endemic Mammals – They include, Colugo or Flying Lemur (Cynocephalus sp.), Tartiar (Tarsius sp. ), Slow Loris (Nycticebus caucaung), Hoolock Gibbon (Hylobates hoolaca),Tree Shrew (Dendrogale sp.), Beaked Porpoise or Fresh Water Dolphin (Platanista gangetica), Pangolin or Ant-eater (Manis crassicaudata), Spactaculated Langur (Trachypithecus phayrei), Capped Langur (Trachypithecus pileatus), Orang Otang (Pongo pygmaeus), Two horned Rhinoceros (Dicerorhinus sumatriensis), Asian Elephant (Elephas indicas), Langur (Semnopithecus entellus), Lion Tailed Macaque (Macaca siamensis), Black Bear (Melarsus ursinus), Antilope (Antilope cervicapra), Gaur (Bos gaurus) etc.
- Endemic Birds – They include, Golden Oriole (Oriolus oriolus), Black Hooded Oriole (Oriolus xanthornus), Green Bulbul (Chloropsis hardwickii), Fairy Blue Bird (Irena puella), White Cacatae (Cacatua alba), Nicobor Parakeet (Pittacula caniceps), Greater Adjutant (Leptoptilos javonicus), Lesser Adjutant (Leptoptilos dubius), Moorhen (Francolinus gularis), Burmease Peafowl (Pavo muticus), Norman’s Green-leg (Tringa guttifer).
- Endemic Reptiles – They include, Comodo Dragon (Varanus komodoensis), Gharial (Gavialis gangeticus), Muggar or Fresh Water Crocodile (Crocodilus palustris), Sylhet Turtle (Kachuga sylhetensis), Greater Turtle (Batagur baska), Common Turtle (Kachuga kachuga), Eastern Egg-eater (Elachistodon westermanni).
- Endemic Amphibians – They include, Striped Tree Frog (Microhyla chakrapani), Garo Hill Frog (Rana garoensis), Daniel’s Frog (Rana denieli), Green Toad (Ramanella minor).
- Endemic Fishes – They include, Tila Shoal (Channa barca), Pabda (Ompik pabda), Mani (Nandus nandus), Green Carp (Labeo fisheri), Tara Bain (Macrognathus oral), Napit Koi (Badis badis), Kunche (Monopterus cuchia), Bacha (Eutropichthyes vacha), Ayir (Aorichthys aor), Chaga, Pangash, Hill Loach, Pike Head etc.

ENVIRONMENTAL PROBLEMS

All organisms, capable of breeding, multiply in course of time and increase in their number in mathematical ratios. According to Charles Darwin, over production, leads to struggle for existence i.e., for shelter, food, reproduction etc. The survival of the fittest leads to the origin of species. It is a natural process. That is how evolution progresses.

Human Population explosion:

Human population is not an exception to Malthusian law of nature, but he is a self centered species. Today the world’s human population is more than six billion. Sadly India and China together have contributed more than 2.4 billion to it. The population explosion has endangered the very existence human species. But it also affecting the other species. In fact the growth rate of human population in exponential pattern started with agricultural revolution and it is still progressing in the same rate though the overall birth rate has remained at 1.7%, but the death rate has drastically decreased. By 2020 the world’s population is expected to be more than 7 billion.

The damage caused by the population explosion and industrial revolution are many, all of them are self destructive: – they are deforestation, environmental pollution etc. In fact all the ecological and environmental problems that the planet earth is experiencing, is mainly due to uncontrolled growth of human population.

Deforestation & its effects:

Forest wealth has been exploited for human needs like shelter, agriculture, transport, fuel etc. What is left today is not even enough for another 3 decades, provided afforestation is taken up on large scale. Massive cutting of trees in Asia and Brazil’s Amazonian virgin forest for commercial exploitation and burning of forests for cultivation is going on unabated. At this rate of destruction i.e., 100 acres per minute, goes on, by 2020 all forests will be destroyed. Not only cutting of trees, even mining has destroyed the vegetation, fauna and even the ecosystems.

Deforestation has upset the balance of the very ecosystem. When producers are destroyed, the dependent animals and their dependents migrate. In the process many of them die.

Deforestation has caused considerable damage to the soil in the form of soil erosion, land slides, and flash floods, loss of minerals and organic matter. All have rendered the soil useless for the growth of flora and fauna.

With the disappearance of vegetation the moisture content of the soil and atmosphere has reduced. As a consequence the annual rain fall has also decreased. All these effects have lead or leading to desertification of the land mass.

Industrial revolution and its effects:

Population explosion has also resulted in the growth of a large number of cities and towns. Another parallel development is the growth of industries. It is the product of human ingenuity. The uncontrolled growth of industries, in cities and towns has caused greater damage to the environment than any other single factor.

Overcrowding & growth of urban centers: Overcrowding of cities and towns has resulted in the development of large number of slums, accumulation garbage, and inundation of large tracks with sewerage water in all conceivable places. Such unhygienic conditions arc threatening millions of people with waterborne, airborne communicable diseases: some of them are of epidemic in nature. A simple mutation in any one of the harmless virus can result into a virulent variety which can wipe out the entire human population before he could realize what has hit him. Such pollutions have also devastating effect on the flora and fauna of the area.
Eutrophication: Human waste and other animal systems in the form of organic waste (N₂), from overly populated areas, entering into large tracts of water body has noxious affect on aquatic ecosystem in the form of cultural Eutrophication. Similarly soil erosion also causes the down flow of many mineral especially phosphate into large body of water. The entry of organic N₂& phosphate etc and other nutrients causes great bloom & luxuriant growth of the floating vegetation. As a consequence the lower lying flora, because of lack of sun light, dies. The detritious forms, utilizing oxygen degrade the dead plants. As a result deoxygenating of water takes place. Many zooplanktons die. This phenomenon is called Eutrophication, which causes greater damage to the said ecosystem.
Land & water pollution: Added to this, industries are spewing out all kinds of obnoxious and poisonous gases into air and discharging waste. Industries are producing more wastes than products. All their waste is dumped either on land or in water. Rivers have been polluted by industrial discharges to such an extent, most of the fresh water forms are either dead or dying. Drinking water for animals is not available for miles. The lands have become uncultivable.
Air pollution & Acid rain: Iron and steel industries & oil refineries & others all over the world are spewing out great amount of CO₂and other gases, industries which arc using carbon as the fuel are darkening the skies with CO₂and carbon monoxide & carbon dust The motionless dark clouds called smog (smoke & fog) hanging the over populated area, bring down the CO₂or phosphorous oxide and SO2 or all in the form of acid rain which has already destroyed many million hectares of million years old rain forests and severely affected the health of millions of animals including human being.
Oil spillage: Oil spillage on land and sea is again destroying a large number of flora & fauna. In recent years oil spillage has become a common phenomenon. The above said pollutants have not only affected human beings but alto devastating all kinds of ecosystems.
Green house effect: The burning of high grade fossil fuel by motor vehicles, dieselized engines, coal based power stations, fertilizer industries, high speed jets etc are polluting the very air we breath with CO, CO₂, NO₂, benzpyrine and other deadly gases.
Industrial output of CO₂and pollutants and large scale burning of forests and the release of heavy amount of CO₂is of great concern to the civilized world. Increase in the concentration of CO, CO₂and other gases is believed to have a devastating green house effect The dense cloud of CO₂and similar materials forming a mantle over the earth, though allow the sun rays to reach the earth’s surface, the long wave length infra red rays or far red rays, radiated back to space are again reflected back to earth, by the clouds causing global warming by 1.5°C to 4.5⁰C. Such global warming results in the melting of a large body of ice collected at the polar caps. This may entail in raising the water level of seven seas, and many cities, towns, located at the shore will be inundated or completely submerged. But to check this devastating consumerism one has to devise alternate technology and make it available to common man, till then one cannot simply say no and put blanket cap to the developing nations and underdeveloped nation who are on the verge of growing, will have greater impact on the national growth. The developed countries won’t be affected, because they can take it.
It is also important to evaluate, whether or not the burning off the fuel by human beings is the lone cause for global warming? The sun of our solar system has passed its half age and it is burning fast with more solar bursts and eruptions which is happening day in and day out. Calculation of solar burning has thousand times more effect on human consumerism. How do you control. People shout that that CO2 among other gases is the main factor that causes global warming; it is not a correct argument. The green plants on this planet whatever left requires more concentration of CO2 for, increase in the concentration from 0.03% to 100 times or more, plants produce more biomass, than what they are doing now. At this point of time the concentration of CO2 in the atmosphere is not enough for full blown photosynthesis till eleven or twelve O’clock in the morning, and the whole day they will be releasing CO2 via photorespiration respiration. Also we have to remember plants in dark are releasing more CO2 than any other systems. So what do you call CO2 is and evil or savior of ecosystem? Living beings also producing and releasing organic gases which have devastating effect on our environment. Until and unless, some cacophony self claimed environmentalists, found in every nook and corner, understand what is what, the real scientists who know the science of global warming, will remain silent spectators. We never understand the CO2 is held by oceanic water, god bless the ecosystem there free of the abuse.
Nuclear pollution: Nuclear wastes in form of used radioactive isotopes are dumped in all unimaginable areas of land and water. In some places they have been washed into drains to join sewage water. Nuclear power stations, one time or the other, due to malfunctions of machines or human beings, spew out vast amount of radiation. Classic examples of Three Mile Island in USA and Chernobyl disaster is USSR have caused irreparable damage to surrounding communities. The piled up nuclear arsenals in the developed world like USA & USSR, even if 1/10 of it is used in any war, or exploded by an accident can, not only devastate the whole area covering 2000 to 5000 square miles and also cause the most dreaded ‘Nuclear Winter
Holes in Ozone mantle: The burning of fuel also releases nitrogen oxides (NO) along with carbon gases, which when react with ozone; the ozone will be destroyed to oxygen. NO+0₃>>>N0₂ + 0₂
Another class of compounds which are used in refrigeration on large scale is Chloro-fluro carbons. On release they interact with ozone, and the ozone layer will be destroyed. From outer space, through satellites, holes in ozone layers in polar regions have been detected. Ozone layer, around the earth is virtually shielding all living organisms on this planet from ultraviolet (UV) radiations emanated from the sun. The ozone layer all these millions of years has absorbed the UV rays and prevented them reaching the surface of the earth. If the ozone layer is destroyed, UV radiation can cause mutations in all living organisms. It is an unimaginable scenario of devastation & destruction when it happens. Fortunately human intervention has now brought back the ozone safty.
Biocides: Modem agricultural methods of cultivation have brought in many benefits to the mankind. But the excessive uses of fertilizers, fungicides and insecticides have polluted the very land where the crop plants are grown. The residuals left in the soil and plant products are not only destroying the micro flora in the soil but also threatening the animal and human beings with all kind of diseases with no cure in sight due to seepage of contaminated water the very water we drink is heavily contaminated.
Hydroelectric & Irrigation projects: Big hydroelectric and irrigation projects are the life lines for the progress of any country. But the backwaters of such dams have submerged vast track of land and destroyed well established ecosystems. In the down stream water logging and salinity have rendered croplands into waste lands.

The overall effect of population explosion on environment is deadly and devastating. Another greatest tragedy, as an offshoot of population explosion, is an increase in illiterate population among the poor as well as an increase in the illiteracy among the literates, about environment & environmental hazards. It looks like, it is beyond the human ingenuity to reclaim and reuse what has been already destroyed and damaged.

MEASURES TO CONSERVE ECOSYSTEMS AND THE ENVIRONMENT

1. Control of population growth: In order to save ecosystem and him and other life forms from human abuse, first man has to check the growth of his own population to a limit before it grows into an uncontrollable “Human time Bomb”. Family planning has to be enforced irrespective of cast or creed.

2. Control the growth of cities & towns: Growth of already over crowded big cities and towns have to be checked from growing still bigger, which is inevitable. The residents should be provided with proper shelter, water, drainage and sanitary facilities.

3. Convert garbage to wealth: Sewerage and garbage have to be properly disposed or collected for reprocessing and reuse. Garbage is not a waste but it can be converted into wealth, if it is properly done.

4. Decentralize industrial centers: At the same time, over crowding of cities and towns with more industries should be halted to check the mass migration of rural population to urban areas. Only sensible Govt. can do it for it is the problem of the nation; in its larger sense it is the problem of the world.

5. Control of pollution: Air pollution, water pollution, soil pollution by hazardous outputs from industries, gasoline burning by motor vehicle, jets & thermal plants, should be controlled by proper

Corrective measures in the form of enforceable laws and honest authorities. Those, who fail to obey the laws, should be severely punished.

6. Purification of Air, water, and Land: Hazardous industries including nuclear plants should be shifted far away from human habitation. All corrective and preventive measures should be undertaken from any kind of miss happenings. Methods to depollute the air, water and land have to be devised by new and innovative technology of 21st century.

7. Reclamation of lands: Saline, water logged and dissertated lands have to be reclaimed for cultivation by innovative technology.

8. Use of Biotechnology: Including genetic engineering, Biotechnology should be used to grow more food in less area. Instead of using degradable or not degradable pesticides or insecticides or fungicides etc, one has to develop new varieties resistant to pests and pathogens, but at the same time they should be high yielding. The frontier technologies in life sciences have to be innovated and applied with war footing. Environmental pollution can be contained by using bioengineering techniques.

9. Afforestation: Soil erosion should be prevented by using recent biological & mechanical methods at any cost Afforestation in all conceivable areas should be undertaken on a massive scale. Social forestry should be encouraged at village level as well as at global level. This has to be done, by consensus environmentalists by educating the public as well as the notorious politicians in power.

10. Mass Education on Environmental problem: Education in this regard, on a large scale in relevant areas and to relevant people is essential. It is essential or imperative to develop infrastructure and technology for educating the mass at rural, semi urban and urban level in Ecology/environmental hazards and of methods that can save the Ecological wealth and to improve the environment Inculcating the knowledge and methods to conserve environment at the level of school children and illiterate mass is more beneficial than educating the so called educated in urban areas.

CONTROVERSY OVER PROGRESS AND CONSERVATION

Progress of a country is measured in terms of its total economics of food production, industrial output, living standards, quality of education, economic viability etc. This depends upon how much of natural wealth is used as the input for the above outputs. Protagonists of exploitation of natural wealth for the progress of the country are one breed of extremists. They are so greedy; they are not satisfied even if one hands over the entire wealth of a country at their disposal. They are the men who have plundered the natural wealth and exploited the human resources in the name of progress. Unfortunately these monsters control Govt. and its administration with remote controls.

There is another group of people, Khadi clad or Kaavi clad with red or green head gears, who call themselves as environmentalists. Greens conversationalists, a “new breed” indeed. Day in and day out, they scream through microphones on big and colorful platforms, “stop cutting trees”, “stop constructing dams” etc. Their patriotism sores to great heights and their intelligence overflows, over a bottle of concoctions. While these people talks big about environment, their household people throw garbage on to streets, spit on the footpath and litter the road and parks with all kinds of things and still blame the Govt. These are the other kind of extremists who make others to believe that talking is progress, obstructing the developmental projects is progress, shouting for political gains is progress. There are some exceptions where people have done good work in this field.

The saner, the pragmatic experts in ecology and environmental sciences and really progressive people believe that progress of the country is not possible without the use of natural wealth. But they want to find ways and means to reuse what has been already thrown away as garbage and urge not to destroy, nor use what is not needed; don’t waste.

Checking the growth of human population is the most important measure to be undertaken with war footing. Without such programs no progress can be made in any place or any time. Over population is the scourge of our society. It outgrows itself into self destructing time bomb. The so-called environmentalists in India, if they have any concern above the conservation of Environment, first they should start campaigning for birth control at all levels of the society to bring down growth rate of human population in India and all over the world.

Industries are required for the progress of the nation but measures have to be taken to prevent wasting the natural wealth and measures to prevent pollution of environment. Precaution and safety methods have to be employed to prevent accidents like Bhopal, Three Mile Island, or Chernobyol.

Afforestation has to be done with great forethought its effect may not be perceived today, but can be felt after fifty or hundred years from now. Reusing of the so called waste has to be done in large scale to prevent further exploitation of the environment. When there are no immediate alternatives one has to use what is available.

It is true that the backwaters of huge dams meant for irrigation and electricity do damage the local flora and fauna. At the same time one should remember that any storage of water is also the starting point for another series ecological succession resulting in an ecosystem. So there is no need to stop the very lifeline of progress.

Conservation studies on protected ecosystems of islands have given few clues how the same methods can be employed on main lands. Govt. laws have to be made and implemented by declaring vast tracts of ecosystems as protected areas in different regions. It is no good to declare inconsequential and small areas as protected. Large areas, having greater number of species of flora & fauna in a given unit area establish themselves to the said ecosystem. Law enforcements should be strict to prevent poaching & deforestation.

Well laid planning has to go into the conservation of ecosystem. No society can survive or progress without the utilizations of forest products. But if plans are, made with future in mind, so that, while cutting of 10 hectares of plantation, there should be 50 hectares of plantation ready and equal area should afforested. This kind of planning entails in not only conserving the ecosystem but also enriches it.

One should bear in mind that progress is not just accumulation of money and material etc, nor can you call yourself progressive just by stopping the cutting of trees, digging minerals from the mines, stopping the construction of huge dams and industrial plants; the real progress should be in human thinking; and it emanates from education and educating. Progress can be achieved when you acquire what is needed and sharing the extra with have-nots. The sharing may be money or material, but sharing the human thought and knowledge is the greatest progress that any man or a country can dream about

An Experiment to determine the Relative density of plant species:

Method: This experiment is conducted in groups. Take the help of teacher in selecting the area and identifying the plant species. Select an area measuring 10 x 10 feet or 20 feet and mark with nails and thread. Count the total number of plants and count the number of each species and note down. Using the given formula calculate the relative density of each species and plot the same on a graph sheet showing the distribution area wise with table. If you find time you can conduct such survey in two or three different plots in different areas containing different flora.

References –

Darlington, Zoogeography
Ehrlich Paul R,, & Ehrlich, Anne H., Population, Resources, Environment – Issues in Human Ecology, W.H.Reeman and Company, San Francisco, 1970
Marsh, George P., The Earth as Modified by Human Action, Charles Scribner’s Sons, New York, 1874
McHargg, Ian, Design with Nature, Natural History Press, Garden City, New York, 1969
Morris, Desmond, The Naked Ape, McGraw-Hill, New York, 1967
Odum, Eugene P., Basic Ecology, 1983.
Odum, Eugene P., Ecological Vignettes: Ecological Approaches to Dealing with Human Predicament, 1998.
Odum, Eugene P., Ecology and Our Endangered Life Support Systems, 1993.
Odum, Eugene P., Ecology, Saunders Pub., UK, 1963
Odum, Eugene P., Ecology, the link between the natural and the social sciences, 1975.
Odum, Eugene P., Essence of Place (co-authored with Martha Odum), 2000.
Odum, Eugene P., Fundamentals of Ecology, with Howard T. Odum. 1953
Odum, Eugene P., The Strategy of Ecosystem Development, 1969.
Odum, Eugene P., Variations in the heart rate of birds: a study in physiological ecology, 1939.