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Environment Introduction Word "environment" is most commonly used describing "natural" environment and means the sum of all living and non-living things that surround an organism, or group of organisms. Environment includes all elements, factors , and conditions that have some impact on growth and development of certain organism Environment includes both biotic and abiotic factors that have influence on observed organism. factors such as light, temperature, water, atmospheric gases combine with biotic factors (all surrounding living species). Environment is sum total of water, air and land, inter-relationships among themselves and also with the human beings, other living organisms and property.‖

Multidisciplinary nature of Environment:Environmental science is now a mature, viable discipline. The past three decades have witnessed a growing awareness of the affects of human activity upon our earth‘s resources and during this period environmental study has emerged as a multi-disciplinary field of study to examine the interaction of the people and their environments It helps us to understand the nature of environment and its components, nature of disturbing factors and the various methods to overcome disturbing factors. The disturbing factors pressurize sustainability and natural living.

Life Sciences:Biology , Microbiology, Biochemistry, Biotechnology etc.

Physical Sciences:Basic & Applied studies Physics, Chemistry ,Earth Science,Atmospheric Science, Oceanography, Geology Modelling

Technology

Environmental Civil Engg., Chemical Engg., Hydraulics, Nanotechnology etc.

Studies

Mathematics , Statistics, Computer Science etc.

Management & Awareness

Economics, Sociology, Law, Education, Management, mass communication

Multidisciplinary Nature of Environmental Stuidies

Scope of Environment:In short scope of environmental studies is broad based and it encompasses a large number of areas and aspects, broadly listed below:

Natural Resources- their conservation and management Ecology and biodiversity Environmental pollution and control Social issues in relation to development and environment Human population and environment In recent years several career options have emerged in this field that are broadly categorized as:1. Research & development in Environment 2. Green Advocacy 3. Green marketing 4. Environmental consultancy 5. Green Media

Ecosystem:An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving (abiotic), physical components of the environment with which the organisms interact, such as air, soil, water and sunlight.

The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem. Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction. Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources. Components of Ecosystem:An

ecosystem

comprises

of

two

basic

ABIOTIC COMPONENTS Sunlight

BIOTIC COMPONENTS Primary producers

Temperature

Herbivores

Precipitation

Carnivores

Water or moisture

Omnivores

Soil or water chemistry (e.g., P, NH4+)

Detritivores

etc. All of these vary over space/time

etc.

components

i) Abiotic components and ii) Biotic components The relationship between the biotic components and abiotic components of an ecosystem is called 'holocoenosis'.

Abiotic Components These include the non-living, physico - chemical factors such as air, water, soil and the basic elements and compounds of the environment. Abiotic factors are broadly classified under three categories. Climatic factors which include the climatic regime and physical factors of the environment like light, humidity, atmospheric temperature, wind, etc. Edaphic factors which are related to the structure and composition of soil including its physical and chemical properties, like soil and its types, soil profile, minerals, organic matter, soil water, soil organisms. Inorganic substances like water, carbon, sulphur, nitrogen, phosphorus and so on. Organic substances like proteins, lipids, carbohydrates, humic substances etc. Biotic Components It comprises the living part of the environment, which includes the association of a number of interrelated populations belonging to different species in a common environment. The populations are that of animal community, plant community and microbial community. Biotic community is distinguished into autotrophs, heterotrophs and saprotrophs.

Autotrophs (Gr: auto - self, trophos - feeder) are also called producers, convertors or transducers. These are photosynthetic plants, generally chlorophyll bearing, which synthesize high-energy complex organic compounds (food) from inorganic raw materials with the help of sunlight, and the process is referred as photosynthesis. Autortophs form the basis of any biotic system. In terrestrial ecosystems, the autotrophs are mainly the rooted plants. In aquatic ecosystems, floating plants called phytoplankton and shallow water rooted plants called macrophytes are the dominant producers. Heterotrophs (Gr: heteros - other; trophs - feeder) are called consumers, which are generally animals feeding on other organisms. Consumer's also referred as phagotrophs (phago - to ingest or swallow) or macroconsumers are mainly herbivores and carnivores. Herbivores are referred as First order consumers or primary consumers, as they feed directly on plants. For e.g., Terrestrial ecosystem consumers like cattle, deer, rabbit, grass hopper, etc. Aquatic ecosystem consumers like protozoans, crustaceans, etc. Carnivores are animals, which feed or prey upon other animals. Primary carnivores or Second order consumers include the animals which feed on the herbivorous animals. For e.g., fox, frog, predatory birds, smaller fishes, snakes, etc. Secondary carnivores or Third order consumers include the animals, which feed on the primary carnivores. For e.g., wolf, peacock, owl, etc. Secondary carnivores are preyed upon by some larger carnivores. Tertiary carnivores or Quaternary consumers include the animals, which feed on the secondary carnivores.

For e.g., lion, tiger, etc. These are not eaten by any other animals. The larger carnivores, which cannot be preyed upon further are called top carnivores.

Saprotrophs (Gr: sapros - rotten; trophos - feeder) are also called decomposers or reducers. They break down the complex organic compounds of dead matter (of plants and animals). Decomposers do not ingest their food. Instead they secrete digestive enzymes into the dead and decaying plant and animal remains to digest the organic material. Enzymes act upon the complex organic compounds of the dead matter. Decomposers absorb a part of the decomposition products for their own nourishment. The remaining substances are added as minerals to the substratum (mineralisation). Released minerals are reused (utilised) as nutrients by the plants (produ Ecological Pyramids An ecological pyramid (also trophic pyramid or energy pyramid) is a graphical representation designed to show the biomass or biomass productivity at each trophic level in a given ecosystem. Ecological pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat herbivores, then carnivores that eat those carnivores, and so on). The highest level is the top of the food chain.

Types of Ecological Pyramids There are three types of pyramids: of numbers, of biomass, and of energy. Pyramid of Biomass Biomass is renewable organic (living) material. A pyramid of biomass is a representation of the amount of energy contained in biomass, at different trophic levels for a particular time. It is measured in grams per meter2, There are two types of biomass pyramids: upright and inverted. An upright pyramid is one where the combined weight of producers is larger than the combined weight of consumers. An example is a forest ecosystem. An inverted pyramid is one where the combined weight of producers is smaller than the combined weight of consumers. An example is an aquatic ecosystem.

Pyramid of Numbers The pyramid of numbers represents the number of organisms in each trophic level. This pyramid consists of a plot of relationships between the number herbivores (primary consumers), first level carnivore (secondary consumers), second level carnivore (tertiary consumers) and so forth. Upright, partly upright and inverted are the three types of pyramids of numbers. An aquatic ecosystem is an example of upright pyramid where the number of organisms becomes fewer and fewer higher up in the pyramid. A forest ecosystem is an example of a partially upright pyramid, as fewer producers support more primary consumers, but there are less secondary and tertiary consumers. An inverted pyramid of numbers is one where the number of organisms depending on the lower levels grows closer toward the apex. A parasitic food chain is an example.

Pyramid of Energy The pyramid of energy represents the total amount of energy consumed by each trophic level. An energy pyramid is always upright as the total amount of energy available for utilization in the layers above is less than the energy available in the lower levels. This happens because during energy transfer from lower to higher levels, some energy is always lost.

Food Chains If an ecosystem is to be self-sustaining it must contain a flow of energy. One way of representing the flow of energy through the living components of an ecosystem is through the use of a food chain. A food chain indicates the transfer of energy from producers through a series of organisms which feed upon each other. A Food Chain The algae and floating plants are the producers in this food chain. The aquatic crustaceans are the primary consumers which eat the producers.

Note that the arrows in the food chain point to the organisms which are doing the eating. Thus the arrows in the food chain represent the flow of energy through the ecosystem.

Fish are secondary consumers eating the primary consumers. A food chain may also contain third level or other consumers as indicated by the raccoons in this food chain.

Food Webs In a natural community, the flow of energy and materials is much more complicated than illustrated by any one food chain. A food web is a series of interrelated food chains which provides a more accurate picture of the feeding relationships in an ecosystem, as more than one thing will usually eat a particular species. A Food Web Energy flow in a food web also starts with the producer organisms through the

various levels of consumer organisms as in a food chain.

The Nitrogen Cycle The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems (Figure 9s-1). Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids. The store of nitrogen found in the atmosphere, where it exists as a gas (mainly N2), plays an important role for life. This store is about one million times larger than the total nitrogen contained in living organisms. Other major stores of nitrogen include organic matter in soil and the oceans. Despite its abundance in the atmosphere, nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4+ ) and the ion nitrate (NO3- ). Most plants obtain the nitrogen they need as inorganic nitrate from the soil solution. Ammonium is used less by plants for uptake because in large concentrations it is extremely toxic. Animals receive the required nitrogen they need for metabolism, growth, and reproduction by the consumption of living or dead organic matter containing molecules composed partially of nitrogen.

Figure 9s-1: Nitrogen cycle.

In most ecosystems nitrogen is primarily stored in living and dead organic matter. This organic nitrogen is converted into inorganic forms when it re-enters the biogeochemical cycle via decomposition. Decomposers, found in the upper soil layer, chemically modify the nitrogen

found in organic matter from ammonia (NH3 ) to ammonium salts (NH4+ ). This process is known as mineralization and it is carried out by a variety of bacteria, actinomycetes, and fungi. Nitrogen in the form of ammonium can be absorbed onto the surfaces of clay particles in the soil. The ion of ammonium has a positive molecular charge is normally held by soil colloids. This process is sometimes called micelle fixation (see Figure 9s-1). Ammonium is released from the colloids by way of cation exchange. When released, most of the ammonium is often chemically altered by a specific type of autotrophic bacteria (bacteria that belong to the genus Nitrosomonas) into nitrite (NO2- ). Further modification by another type of bacteria (belonging to the genus Nitrobacter) converts the nitrite to nitrate (NO3- ). Both of these processes involve chemical oxidation and are known as nitrification. However, nitrate is very soluble and it is easily lost from the soil system by leaching. Some of this leached nitrate flows through the hydrologic system until it reaches the oceans where it can be returned to the atmosphere by denitrification. Denitrification is also common in anaerobic soils and is carried out by heterotrophic bacteria. The process of denitrification involves the metabolic reduction of nitrate (NO3- ) into nitrogen (N2) or nitrous oxide (N2O) gas. Both of these gases then diffuse into the atmosphere. Almost all of the nitrogen found in any terrestrial ecosystem originally came from the atmosphere. Significant amounts enter the soil in rainfall or through the effects of lightning. The majority, however, is biochemically fixed within the soil by specialized micro-organisms like bacteria, actinomycetes, and cyanobacteria. Members of the bean family (legumes) and some other kinds of plants form mutualistic symbiotic relationships with nitrogen fixing bacteria. In exchange for some nitrogen, the bacteria receive from the plants carbohydrates and special structures (nodules) in roots where they can exist in a moist environment. Scientists estimate that biological fixation globally adds approximately 140 million metric tons of nitrogen to ecosystems every year. Water cycle

The sun, which drives the water cycle, heats water in oceans and seas. Water evaporates as water vapor into the air. Ice and snow can sublimate directly into water vapor. Evapotranspiration is water transpired from plants and evaporated from the soil. Rising air currents take the vapor up into the atmosphere where cooler temperatures cause it to condense into clouds. Air currents move water vapor around the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow or hail, sleet, and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Snowpacks can thaw and melt and the melted water flows over land as snowmelt. Most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff and groundwater are stored as freshwater in lakes. Not all runoff flows into rivers, much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers, which store freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge. Some groundwater finds openings in the land surface and comes out as freshwater springs. Over time, the water returns to the ocean, where our water cycle started. Carbon cycle Carbon exists in the Earth's atmosphere primarily as the gas carbon dioxide (CO2). Although it is a small percentage of the atmosphere (approximately 0.04% on a molar basis), it plays a vital role in supporting life. Other gases containing carbon in the atmosphere are methane and chlorofluorocarbons (the latter is entirely anthropogenic). Trees and other green plants such as grass convert carbon dioxide into carbohydrates during photosynthesis, releasing oxygen in the process. This process is most prolific in relatively new forests where tree growth is still rapid. The effect is strongest in deciduous forests during spring leafing out. This is visible as an annual signal in the Keeling curve of measured CO2 concentration. Northern hemisphere spring predominates, as there is far more land in temperate latitudes in that hemisphere than in the southern. Forests store 86% of the planet's terrestrial above-ground carbon and 73% of the planet's soil carbon. At the surface of the oceans towards the poles, seawater becomes cooler and more carbonic acid is formed as CO2 becomes more soluble. This is coupled to the ocean's thermohaline circulation which transports dense surface water into the ocean's interior (see the entry on the solubility pump). In upper ocean areas of high biological productivity, organisms convert reduced carbon to tissues, or carbonates to hard body parts such as shells and tests. These are, respectively, oxidized (soft-tissue pump) and redissolved (carbonate pump) at lower average levels of the ocean than those at which they formed, resulting in a downward flow of carbon (see entry on the biological pump). The weathering of silicate rock (see carbonate-silicate cycle). Carbonic acid reacts with weathered rock to produce bicarbonate ions. The bicarbonate ions produced are carried to the ocean, where they are used to make marine carbonates. Unlike dissolved CO2 in equilibrium or tissues which decay weathering does not move the carbon into a reservoir from which it can readily return to the atmosphere.

In 1958, atmospheric carbon dioxide at Mauna Loa was about 320 parts per million (ppm), and in 2011 it is about 391ppm. Future CO2 emission can be calculated by the kaya identity Carbon is released into the atmosphere in several ways: Through the respiration performed by plants and animals. This is an exothermic reaction and it involves the breaking down of glucose (or other organic molecules) into carbon dioxide and water. Through the decay of animal and plant matter. Fungi and bacteria break down the carbon compounds in dead animals and plants and convert the carbon to carbon dioxide if oxygen is present, or methane if not. Through combustion of organic material which oxidizes the carbon it contains, producing carbon dioxide (and other things, like water vapor). Burning fossil fuels such as coal, petroleum products, and natural gas releases carbon that has been stored in the geosphere for millions of years. Burning agrofuels also releases carbon dioxide which has been stored for only a few years or less. Production of cement. Carbon dioxide is released when limestone (calcium carbonate) is heated to produce lime (calcium oxide), a component of cement. At the surface of the oceans where the water becomes warmer, dissolved carbon dioxide is released back into the atmosphere. Volcanic eruptions and metamorphism release gases into the atmosphere. Volcanic gases are primarily water vapor, carbon dioxide and sulfur dioxide. The carbon dioxide released is roughly equal to the amount removed by silicate weathering;[citation needed] so the two processes, which are the chemical reverse of each other, sum to roughly zero, and do not affect the level of atmospheric carbon dioxide on time scales of less than about 100,000 years. In the biosphere Carbon is an essential part of life on Earth. About half the dry weight of most living organisms is carbon. It plays an important role in the structure, biochemistry, and nutrition of all living cells. Living biomass holds about 575 gigatons of carbon, most of which is wood. Soils hold approximately 1,500 gigatons, mostly in the form of organic carbon, with perhaps a third of that inorganic forms of carbon such as calcium carbonate. Autotrophs are organisms that produce their own organic compounds using carbon dioxide from the air or water in which they live. To do this they require an external source of energy. Almost all autotrophs use solar radiation to provide this, and their production process is called photosynthesis. A small number of autotrophs exploit chemical energy sources in a process called chemosynthesis. The most important autotrophs for the carbon cycle are trees in forests on land and phytoplankton in the Earth's oceans. Photosynthesis follows the reaction 6CO2 + 6H2O → C6H12O6 + 6O2 Carbon is transferred within the biosphere as heterotrophs feed on other organisms or their parts (e.g., fruits). This includes the uptake of dead organic material (detritus) by fungi and bacteria for fermentation or decay.

Most carbon leaves the biosphere through respiration. When oxygen is present, aerobic respiration occurs, which releases carbon dioxide into the surrounding air or water, following the reaction C6H12O6 + 6O2 → 6CO2 + 6H2O. Otherwise, anaerobic respiration occurs and releases methane into the surrounding environment, which eventually makes its way into the atmosphere or hydrosphere (e.g., as marsh gas or flatulence). Burning of biomass (e.g. forest fires, wood used for heating, anything else organic) can also transfer substantial amounts of carbon to the atmosphere Carbon may also be circulated within the biosphere when dead organic matter (such as peat) becomes incorporated in the geosphere. Animal shells of calcium carbonate, in particular, may eventually become limestone through the process of sedimentation. Much remains to be learned about the cycling of carbon in the deep ocean. For example, a recent discovery is that larvacean mucus houses (commonly known as "sinkers") are created in such large numbers that they can deliver as much carbon to the deep ocean as has been previously detected by sediment traps.[6] Because of their size and composition, these houses are rarely collected in such traps, so most biogeochemical analyses have erroneously ignored them.

Types of Ecosystem 1.The Forest Ecosystem The forest ecosystem covers the flora, fauna and ground conditions with in the parameters of a forest. From the climatic conditions to the members and relationships in the food chain, the forest ecosystem is dependent on the major resources available. In the forest ecosystem the proportion of flora, including the varieties of trees, grasses, fungi and flowers will effect the way in which fauna exist. The fauna in a forest ecosystem will include the minute and the massive. The forest ecosystem offers shelter and living conditions to insects, birds, arachnids and mammals, from the tiny bush mouse to the largest primate or predator. Tropical rainforest

An area of the Amazon Rainforest in Brazil. The tropical rainforests of South America contain the largest diversity of species on Earth A tropical rainforest is a place roughly within 28 degrees north or south of the equator (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). They are found in Asia, Australia, Africa, South America, Central America, Mexico and on many of the Pacific Islands. Within the World Wildlife Fund's biome classification, tropical rainforests are thought to be a type of tropical wet forest (or tropical moist broadleaf forest)

Amazon river rain forest in Peru Rainforests are forests characterized by high rainfall. This often results in poor soils due to leaching of soluble nutrients. Minimum normal annual rainfall between 175 cm (69 in) and 200 cm (79 in) occurs in this climate region. Mean monthly temperatures exceed 18 °C (64 °F) during all months of the year. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests. Forest Structure The undergrowth or understory in a rainforest is often restricted by the lack of sunlight at ground level, and generally consists of shade-tolerant shrubs, herbs, ferns, small trees, and large woody vines which climb into the trees to capture sunlight. Rainforests are divided into different strata, or layers. The vegetation is organized into a vertical pattern from the top of the soil to the canopy Each with different plants and animals adapted for life in that particular area. Only the emergent layer is unique to tropical rainforests, while the others are also found in temperate rainforests. Emergent layer The emergent layer contains a small number of very large trees called emergents, which grow above the general canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. They need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Eagles, Butterfly|butterflies, bats and certain monkeys inhabit this layer.

The canopy at the Forest Research Institute Malaysia Canopy layer The canopy is the primary layer of the forest forming a roof over the two remaining layers. It contains the majority of the largest trees, typically 30–45 m tall. Tall, broad-leaved evergreen trees are the dominant plants. The densest areas of biodiversity are found in the forest canopy, as it often supports a rich flora of epiphytes, including orchids, bromeliads, mosses, and lichens. These epiphytic plants attach to trunks and branches and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. Many species of birds inhabit this area as well as other taxa including: snakes, tree frogs, and insects. A quarter of all insect species are believed to exist in the rainforest canopy. Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it Understory layer The understory layer lies between the canopy and the forest floor. The understory is home to a number of birds, small mammals, insects, and reptiles, as well as predators such as jaguars, boa (genus)|boa constrictors and leopards. Only about 5% of the sunlight shining on the rainforest canopy reaches the understory so plants seldom grow to 3 m (10 feet) although the leaves are much larger at this level so as to obtain sufficient sunlight. Insect life is also abundant. Many seedlings that will grow to the canopy level are present in the understory. This layer can be called a shrub layer, although the shrub layer may also be considered a separate layer. Forest floor

Rainforest in the Blue Mountains, Australia

The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks, swamps and clearings, where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. This makes it easy to walk through undisturbed, mature rainforest allowing for movement of animals such as: ungulates like the Okapi, rodents like capybaras, larger mammals like tapirs and gorillas, as well as many species of herptiles and insects. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs and small trees, called a jungle. It also contains decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay the animal and plant waste. A leaf that might take one year to decompose in a regular climate will disappear in 6 weeks. Temperate forest Temperate forests correspond to forest concentrations formed in the northern hemisphere. Main characteristics include: wide leaves, big and tall trees and non seasonal vegetation. Specific information should be inquired for each of the different types of Temperate Forests. Temperate deciduous forest Temperate broadleaf and mixed forests Temperate coniferous forest Temperate rainforest

Temperate Forests The term ‗temperate forest‘ is very broad. It covers the forests found between the tropical and subtropical regions and the barren, treeless lands of the far north and extreme south. There are many types of temperate forests, but the main categories are: coniferous forests, mixed broadleaved/ coniferous forests; and broadleaved forests. Mediterranean forests Within each of these categories there are many different subtypes of forest. The kind of forest that can grow depends on local soils, temperatures and rainfall. For example, in southern Europe, long hot summers encourage the growth of a special kind of vegetation called the Mediterranean scrublands. Although they rarely grow thickly enough to be called a true forest, the trees in the Mediterranean scrub lands include small oaks and pines. A characteristic tree of these lands is the cork-oak, which occurs naturally but is also planted for its valuable bark. Overgrazing by sheep and goats has changed much of the once-forested areas of the Mediterranean into scrubland known as ‗maquis‘. Mediterranean scrublands are rich in wildflowers and birds, especially insect-eating birds which are abundant in summer. One of the most spectacular birds found here is the azure-winged magpie.

Temperate forests of the world. © WWF Wildlife in Temperate Forests Kangaroo Giant Panda Related links Temperate Broadleaf and Mixed Forest Ecoregions Temperate Coniferous Forest Ecoregions Mediterranean Forests, Woodlands and Scrub Ecoregions Temperate rainforests Some temperate forests receive so much rain they are sometimes called rainforests! The great Douglas fir and hemlock forests of the United States' Pacific Northwest and Canada's British Colombia receive more than 2,000 mm of rain a year. They are dominated by coniferous trees. Another type of temperate, evergreen rainforest occurs in Chile, South America. Here there is a great diversity of broadleaved trees including the Southern Beech. Deciduous forests Broadleaved trees have big, thin-skinned leaves which allow them to absorb maximum sunlight. These leaves are delicate and vulnerable to winter winds, frost and snow. Broadleaved trees that grow in colder areas shed their leaves in winter - they are deciduous. In autumn, the leaves turn beautiful shades of red, orange and yellow before they drop off the trees. Common deciduous trees are the oak, elm and beech. Others are maple, lime and chestnut. In much of the northern hemisphere, most of the natural broadleaved forests have been cut down to provide farmlands. Forests survive only in small patches, or on mountains. The only large areas of forest left are the coniferous forests of northern Scandinavia, Siberia, the north western United States, Canada and Alaska. Even here, there are few areas of forest left that are in their natural state. Temperate forests are simpler in structure than tropical forests and support a smaller number of tree species.

Temperate coniferous forest is a terrestrial biome found in temperate regions of the world with warm summers and cool winters and adequate rainfall to sustain a forest. In most temperate coniferous forests, evergreen conifers predominate, while some are a mix of conifers and broadleaf evergreen trees and/or broadleaf deciduous trees. Temperate evergreen forests are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or mountain areas. Many species of trees inhabit these forests including cedar, cypress, douglas-fir, fir, juniper, kauri, pine, podocarpus, spruce, redwood and yew. The understory also contains a wide variety of herbaceous and shrub species.

A pine forest is an example of a temperate coniferous forest Structurally, these forests are rather simple, generally consisting of two layers: an overstory and understory. Some forests may support an intermediate layer of shrubs. Pine forests support an herbaceous understory that is generally dominated by grasses and herbaceous perennials, and are often subject to ecologically important wildfires.

Carpathian montane conifer forest, Slovakia Temperate rain forests occur only in seven regions around the world: the Pacific temperate rain forests of the Pacific Northwest, the Valdivian temperate rain forests of southwestern South America, the rain forests of New Zealand and Tasmania, northwest Europe (small pockets in Ireland, Scotland, Wales, Iceland and a somewhat larger area in Norway), southern Japan, and the eastern Black Sea-Caspian Sea region of Turkey and Georgia to northern Iran. The moist conditions of temperate rain forests generally support an understory of mosses, ferns and some shrubs. Temperate rain forests can be temperate coniferous forests or temperate broadleaf and mixed forests. The temperate coniferous rain forests sustain the highest levels of biomass in any terrestrial ecosystem and are notable for trees of massive proportions, including Giant Sequoia

(Sequoiadendron gigantea), Coast Redwood (Sequoia sempervirens), Douglas-fir (Pseudotsuga menziesii), Sitka Spruce (Picea sitchensis), Alerce (Fitzroya cupressoides) and Kauri (Agathis australis). These forests are quite rare, occurring in small areas of North America, southwestern South America and northern New Zealand. The Klamath-Siskiyou forests of northwestern California and southwestern Oregon is known for its rich variety of plant and animal species, including many endemic species 2. Grassland .

A grassland in the Antelope Valley, California Grasslands are areas where the vegetation is dominated by grasses (Poaceae) and other herbaceous (non-woody) plants (forbs). However, sedge (Cyperaceae) and rush (Juncaceae) families can also be found. Grasslands occur naturally on all continents except Antarctica. In temperate latitudes, such as northwestern Europe and the Great Plains and California in North America, native grasslands are dominated by perennial bunch grass species, whereas in warmer climates annual species form a greater component of the vegetation. Grasslands are found in most ecoregion of the Earth. For example there are five terrestrial ecoregion classifications (subdivisions) of the temperate grasslands, savannas, and shrublands biome ('ecosystem'), which is one of eight terrestrial ecozones of the Earth's surface.

Vegetation Grassland vegetation can vary in height from very short, as in chalk where the vegetation may be less than 30 cm (12 in) high, to quite tall, as in the case of North American tallgrass prairie, South American grasslands and African savanna. Woody plants, shrubs or trees, may occur on some grasslands - forming savannas, scrubby grassland or semi-wooded grassland, such as the African savannas or the Iberian dehesa. Such grasslands are sometimes referred to as wood-pasture or woodland.

As flowering plants, grasses grow in great concentrations in climates where annual rainfall ranges between 500 and 900 mm (20 and 35 in). The root systems of perennial grasses and forbs form complex mats that hold the soil in place. Climate Natural grasslands primarily occur in regions that receive between 250 and 900 mm (9.8 and 35 in) of rain per year, as compared with deserts, which receive less than 250 mm (9.8 in) and tropical rainforests, which receive more than 2,000 mm (79 in). Anthropogenic grasslands often occur in much higher rainfall zones, as high as 200 cm (79 in) annual rainfall. Grassland can exist naturally in areas with higher rainfall when other factors prevent the growth of forests, such as in serpentine barrens, where minerals in the soil inhibit most plants from growing. Average daily temperatures range between -20 and 30 °C. Temperate grasslands have warm summers and cold winters with rain or some snow. Grasslands are of vital importance for raising livestock for human consumption and for milk and other dairy products. Grassland vegetation remains dominant in a particular area usually due to grazing, cutting, or natural or manmade fires, all discouraging colonisation by and survival of tree and shrub seedlings. Some of the world's largest expanses of grassland are found in African savanna, and these are maintained by wild herbivores as well as by nomadic pastoralists and their cattle, sheep or goats. Grasslands may occur naturally or as the result of human activity. Grasslands created and maintained by human activity are called anthropogenic grasslands. Hunting peoples around the world often set regular fires to maintain and extend grasslands, and prevent fire-intolerant trees and shrubs from taking hold. The tallgrass prairies in the American Midwest may have been extended eastward into Illinois, Indiana, and Ohio by human agency. Much grassland in northwest Europe developed after the Neolithic Period, when people gradually cleared the forest to create areas for raising their livestock. Grassland types ( biomes ) Tropical and subtropical grasslands These grasslands are classified with tropical and subtropical savannas and shrublands as the tropical and subtropical grasslands, savannas, and shrublands biome. Notable tropical and subtropical grasslands include the Llanos grasslands of northern South America. Temperate grasslands Mid-latitude grasslands, including the Prairie and Pacific Grasslands of North America, the Pampas of Argentina, Brazil and Uruguay, calcareous downland, and the steppes of Europe. They are classified with temperate savannas and shrublands as the temperate grasslands,

savannas, and shrublands biome. Temperate grasslands are the home to many large herbivores, such as bison, gazelles, zebras, rhinoceroses, and wild horses. Carnivores like lions, wolves and cheetahs and leopards are also found in temperate grasslands. Other animals of this region include: deer, prairie dogs, mice, jack rabbits, skunks, coyotes, snakes, fox, owls, badgers, blackbirds (both Old and New World varieties), grasshoppers, meadowlarks, sparrows, quails, hawks and hyenas.

Negri-Nepote Temperate Grasslands in New Jersey Flooded grasslands Grasslands that are flooded seasonally or year-round, like the Everglades of Florida, the Pantanal of Brazil, Bolivia and Paraguay or the Esteros del Ibera in Argentina.They are classified with flooded savannas as the flooded grasslands and savannas biome and occur mostly in the tropics and subtropics. Watermeadows are grasslands that are deliberately flooded for short periods. Montane grasslands High-altitude grasslands located on high mountain ranges around the world, like the Páramo of the Andes Mountains. They are part of the montane grasslands and shrublands biome and also constitute tundra. Tundra grasslands Similar to montane grasslands, polar arctic tundra can have grasses, but high soil moisture means that few tundras are grass-dominated today. However, during the Pleistocene ice ages, a polar grassland known as steppe-tundra occupied large areas of the Northern hemisphere. These are in the tundra biome.

Desert and xeric grasslands Also called desert grasslands, this is composed of sparse grassland ecoregions located in the deserts and xeric shrublands biome. Fauna Mites, insect larvae, nematodes and earthworms inhabit deep soil, which can reach 6 metres (20 ft) underground in undisturbed grasslands on the richest soils of the world. These invertebrates, along with symbiotic fungi, extend the root systems, break apart hard soil, enrich it with urea and other natural fertilizers, trap minerals and water and promote growth. Some types of fungi make the plants more resistant to insect and microbial attacks. Grassland in all its form supports a vast variety of mammals, reptiles, birds, and insects. Typical large mammals include the Blue Wildebeest, American Bison, Giant Anteater and Przewalski's Horse. While grasslands in general support diverse wildlife, given the lack of hiding places for predators, the African savanna regions support a much greater diversity in wildlife than do temperate grasslands. There is evidence for grassland being much the product of animal behaviour and movement; some examples include migratory herds of antelope trampling vegetation and African Bush Elephants eating Acacia saplings before the plant has a chance to grow into a mature tree 3. Desert A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than 400 millimetres (16 in). A common definition distinguishes between true deserts, which receive less than 250 millimetres (10 in) of average annual precipitation, and semideserts or steppes, which receive between 250 millimetres (10 in) and 400 to 500 millimetres (16 to 20 in).

Deserts can also be described as areas where more water is lost by evapotranspiration than falls as precipitation. In the Köppen climate classification system, deserts are classed as BWh (hot desert) or BWk (temperate desert). In the Thornthwaite climate classification system, deserts would be classified as arid megathermal climates.

Classification In 1961, Peveril Meigs divided desert regions on Earth into three categories according to the amount of precipitation they received. In this now widely accepted system, extremely arid lands have at least 12 consecutive months without rainfall, arid lands have less than 250 mm (10 in) of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 mm (10–20 in). Arid and extremely arid lands are deserts, and semiarid areas are generally referred to as steppes. Definition Measurement of rainfall alone cannot provide an accurate definition of what a desert is because being arid also depends on evaporation, which depends in part on temperature. For example, Phoenix, Arizona receives less than 250 millimeters (10 in) of precipitation per year, and is immediately recognized as being located in a desert due to its arid adapted plants. The North Slope of Alaska's Brooks Range also receives less than 250 millimeters (10 in) of precipitation per year and is often classified as a cold desert. Other regions of the world have cold deserts, including areas of the Himalayas and other high altitude areas in other parts of the worldPolar deserts cover much of the ice free areas of the arctic and Antarctic. Potential evapotranspiration supplements the measurement of rainfall in providing a scientific measurement-based definition of a desert. The water budget of an area can be calculated using the formula P − PE ± S, wherein P is precipitation, PE is potential evapotranspiration rates and S is amount of surface storage of water. Evapotranspiration is the combination of water loss through atmospheric evaporation and through the life processes of plants. Potential evapotranspiration, then, is the amount of water that could evaporate in any given region. As an example, Tucson, Arizona receives about 300 millimeters (12 in) of rain per year, however about 2500 millimeters (100 in) of water could evaporate over the course of a year.[citation needed] In other words, about 8 times more water could evaporate from the region than actually falls. Rates of evapotranspiration in cold regions such as Alaska are much lower because of the lack of heat to aid in the evaporation process. There are different forms of deserts. Cold deserts can be covered in snow or ice; frozen water unavailable to plant life. These are more commonly referred to as tundra if a short season of abovefreezing temperatures is experienced, or as an ice cap if the temperature remains below freezing year-round, rendering the land almost completely lifeless. Most non-polar deserts are hot in the day and chilly at night (for the latitude) because of the lack of the moderating effect of water. In some parts of the world, deserts are created by a rain shadow effect in which air masses lose much of their moisture as they move over a mountain range; other areas are arid by virtue of being very far from the nearest available sources of moisture.

The Agasthiyamalai hills cut off Tirunelveli in India from the monsoons, creating a rainshadow region. Deserts are also classified by their geographical location and dominant weather pattern as trade wind, mid-latitude, rain shadow, coastal, monsoon, or polar deserts. Former desert areas presently in non-arid environments are paleodeserts. Montane deserts are arid places with a very high altitude; the most prominent example is found north of the Himalayas, especially in Ladakh region of Jammu and Kashmir, in parts of the Kunlun Mountains and the Tibetan Plateau. Many locations within this category have elevations exceeding 3,000 meters (10,000 ft) and the thermal regime can be hemiboreal. These places owe their profound aridity (the average annual precipitation is often less than 40 mm or 1.5 in) to being very far from the nearest available sources of moisture. Montane deserts are normally cold. Rain shadow deserts form when tall mountain ranges block clouds from reaching areas in the direction the wind is going. As the air moves over the mountains, it cools and moisture condenses, causing precipitation on the windward side. When that air reaches the leeward side, it is dry because it has lost the majority of its moisture, resulting in a desert. The air then warms, expands, and blows across the desert. The warm, desiccated air takes with it any remaining moisture in the desert.

4. Aquatic Ecosystem

An estuary mouth and coastal waters, part of an aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Types Marine Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into the following zones: oceanic (the open part of the ocean where animals such as whales, sharks, and tuna live); profundal (bottom or deep water); benthic (bottom substrates); intertidal (the area between high and low tides); estuaries; salt marshes; coral reefs; and hydrothermal vents (where chemosynthetic sulfur bacteria form the food base). Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Fish caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas Freshwater Main article: Freshwater ecosystem Freshwater ecosystems cover 0.80% of the Earth's surface and inhabit 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish species. There are three basic types of freshwater ecosystems: Lentic: slow-moving water, including pools, ponds, and lakes. Lotic: rapidly-moving water, for example streams and rivers. Wetlands: areas where the soil is saturated or inundated for at least part of the time.

Lake ecosystems can be divided into zones: pelagic (open offshore waters); profundal; littoral (nearshore shallow waters); and riparian (the area of land bordering a body of water). Two important subclasses of lakes are ponds, which typically are small lakes that intergrade with wetlands, and water reservoirs. Many lakes, or bays within them, gradually become enriched by nutrients and fill in with organic sediments, a process called eutrophication. Eutrophication is accelerated by human activity within the water catchment area of the lake.

Freshwater ecosystem. The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. These distinctions forms the basis for the division of rivers into upland and lowland rivers. The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a canopy derive the majority of their food base from algae. Anadromous fish are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species. Wetlands are dominated by vascular plants that have adapted to saturated soil. Wetlands are the most productive natural ecosystems because of the proximity of water and soil. Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. Their closeness to lakes and rivers means that they are often developed for human settlement. Ponds These are a specific type of freshwater ecosystems that are largely based on the autotroph algae which provide the base trophic level for all life in the area. The largest predator in a pond ecosystem will normally be a fish and in-between range smaller insects and microorganisms. It may have a scale of organisms from small bacteria to big creatures like water snakes, beetles, water bugs, frogs, tadpoles, and turtles. This is important for the environment. Oceans An ocean (from Greek Ὠκεανὸς, "okeanos" Oceanus) is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (~3.6×108 km2

) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over 3,000 metres (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (‰) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ‰. Scientists estimate that 230,000 marine species are currently known, but the total could be up to 10 times that number. Oceans can be divided up into the coastal zone and the open sea. Here we will give an explanation of the various types of life zones found in the coastal zone and in the open ocean, along with a schematic overview of all these life zones.

Coastal life zones The coastal zone makes up only 10% of the oceanic environment, but it contains 90% of all marine species. Coastal zones are the most nutrient-rich life zones of the oceans. Coastal zones can be divided up into several different life zones. One life zone that can be found in a coastal zone is an estuary. Estuaries are enclosed areas of coastal water where seawater mixes with freshwater from inland streams and rivers. Temperatures and salinity levels of estuaries always depend upon the size of the flow from saltwater oceans and freshwater rivers and streams. Another life zone found in a coastal zone is a coastal wetland. Wetlands are land that is covered with salt water all or part of the year. Coastal wetlands are the life zones for a number of species and they are popular recreation points. They aid the maintenance of the coastal water quality by filtering and settling out pollutants and nutrients. Coastal wetlands are particularly important because they protect coastal land from flooding and from damage and erosion caused by storms. In the United States there are many coastal wetlands. Examples are bays and lagoons. Examples of plant and animal species found commonly on coastal wetlands are grasses and shrimps. Along tropical coasts with too much silt for coastal wetlands we may find swamps. These help protect the coastline from erosion and are the environment for over 2,000 species of fish, birds and plants. In clear and warm coastal waters of tropics and subtropics, coral reefs may form. Coral reefs are the most biologically divers aquatic life zones. In coral reefs many species live and interact with one another in complex ecological relationships. An example of a large coral reef is the Great Barrier Reef in Australia.

Open ocean life zones The open sea contains only about 10% of all marine species. The open ocean is divided up into three life zones, the euphotic zone, the bathyal zone and the abyssal zone. The subdivision is

based on the penetration of sunlight. The euphotic zone is the upper oceanic zone, where producer species produce oxygen. Nutrient levels are low and dissolved oxygen levels are high. The euphotic zone makes up about 90% of the oceanic surface, whereas only about 10% of the world's fish species are found here. Sunlight penetration rates are high in this oceanic zone. The bathyal zone is hardly lit and the abyssal zone is very dark. These zones are only found in the open sea and do not contain any producers, because of a lack of penetrating sunlight. In the abyssal zone the water is very cold and dissolved oxygen levels are very low. There are high nutrient levels that support many of the species found in the open water. Below the abyssal zone, on the bottom of the ocean, there are many species of decomposers, which break down the organic material of dead oceanic organisms into nutrients. The open ocean has a very high productivity. This makes the above-mentioned life zones of great importance.

Overview of oceanic life zones:

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps are like tiny sea anemones, to which they are closely related. Unlike sea anemones, coral polyps secrete hard carbonate exoskeletons which support and protect their bodies. Reefs grow best in warm, shallow, clear, sunny and agitated waters. Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $US375 billion. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature. They are

under threat from climate change, ocean acidification, blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices, including urban and agricultural runoff and water pollution, which can harm reefs by encouraging excess algae growth.

Live coral are small animals embedded in calcium carbonate shells. It is a mistake to think of coral as plants or rocks. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes. Polyps are usually tiny, but they can range in size from a pinhead to 12 inches (30 cm) across. Reef-building or hermatypic corals live only in the photic zone (above 50 m), the depth to which sufficient sunlight penetrates the water, allowing photosynthesis to occur. Coral polyps do not themselves photosynthesize, but have a symbiotic relationship with zooxanthellae; these organisms live within the tissues of polyps and provide organic nutrients that nourish the polyp. Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight. Without their symbionts, coral growth would be too slow for the corals to form significant reef structures. Corals get up to 90% of their nutrients from their symbionts.

Mangroves Mangroves are marine tidal forests and they are most luxuriant around the mouthsof large rivers and in sheltered bays and are found mainly in tropical countries where annual rainfall is fairly high. Mangrove plants include trees, shrubs, ferns and palms. These plants are found in the tropics and sub-tropics on riverbanks and along coastlines, being unusually adapted to anaerobic conditions of both salt and fresh water environments. These plants have adapted to muddy, shifting, saline conditions. They produce stilt roots, which project above the mud and water in order to absorb oxygen. Mangrove plants form communities which help to stabilize banks and coastlines and become home to many types of animals.

Biodiversity:Biodiversity is the variety and differences among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are a part. This includes genetic diversity within and between species and of ecosystems. Thus, in essence, biodiversity represents all life. India is one of the mega biodiversity centres in the world and has two of the world's 18 ‗biodiversity hotspots‘ located in the Western

Ghats and in the Eastern Himalayas (Myers 1999). The forest cover in these areas is very dense and diverse and of pristine beauty, and incredible biodiversity.

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions support fewer species. Rapid environmental changes typically cause mass extinctions. One estimate is that less than 1% of the species that have existed on Earth are extant. Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. The next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of plant and animal life. The Permian–Triassic extinction event, 251 million years ago, was the worst; vertebrate recovery took 30 million years. The most recent, the Cretaceous–Tertiary extinction event, occurred 65 million years ago, and has often attracted more attention than others because it resulted in the extinction of the dinosaurs.

This multilevel construct is consistent with Dasmann and Lovejoy. An explicit definition consistent with this interpretation was first given in a paper by Bruce A. Wilcox commissioned by the International Union for the Conservation of Nature and Natural Resources (IUCN) for the 1982 World National Parks Conference. Wilcox's definition was "Biological diversity is the variety of life forms...at all levels of biological systems (i.e., molecular, organismic, population, species and ecosystem)...". The 1992 United Nations Earth Summit defined "biological diversity" as "the variability among living organisms from all sources, including, 'inter alia', terrestrial, marine, and other aquatic ecosystems, and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems". This definition is used in the United Nations Convention on Biological Diversity. Hotspots A biodiversity hotspot is a region with a high level of endemic species. Hotspots were first named in 1988 by Dr. Sabina Virk. Many hotspots have large nearby human populations. While hotspots are spread all over the world, the majority are forest areas and most are located in the tropics. Brazil's Atlantic Forest is considered one such hotspot, containing roughly 20,000 plant species, 1,350 vertebrates, and millions of insects, about half of which occur nowhere else. The island of Madagascar, particularly the unique Madagascar dry deciduous forests and lowland rainforests,

possess a high ratio of endemism. Since the island separated from mainland Africa 65 million years ago, many species and ecosystems have evolved independently. Indonesia's 17,000 islands cover 735,355 square miles (1,904,560 km2) contain 10% of the world's flowering plants, 12% of mammals and 17% of reptiles, amphibians and birds—along with nearly 240 million people. Many regions of high biodiversity and/or endemism arise from specialized habitats which require unusual adaptations, for example alpine environments in high mountains, or Northern European peat bogs. Accurately measuring differences in biodiversity can be difficult. Selection bias amongst researchers may contribute to biased empirical research for modern estimates of biodiversity. In 1768 Rev. Gilbert White succinctly observed of his Selborne, Hampshire "all nature is so full, that that district produces the most variety which is the most examined." Value of Biodiversity:Economic benefits, both direct and indirect; Aesthetic benefits; Scientific and ethical knowledge; Insurance against the future

Population diversity While we often hear about species, what we generally see and interact with are populations distinct groups of members of a particular species that have a limited exchange of genetic material among the groups. They can reproduce together but they don't often do so.

Extreme population variability can be a double-edged sword. For example, lake trout in Ontario's Great Lakes were once very diverse. There were at least 15 to 20 different forms of lake trout recognized by commercial fishermen before the sea lamprey appeared. The lake trout differed in where they were found, when they spawned, and in their appearance. They were given such names as blacks, redfins, yellowfins, paper bellies, fats, humpers and sand trout. Undoubtedly, the number of genetically distinct populations was much higher. However, even all this diversity could not withstand over-harvest, sea lamprey predation and loss of habitat, particularly inshore rubble shoals required for spawning. The catches of lake trout plunged to 10% of the original yield in Lake Superior and down to almost nothing in the other Great Lakes. When conditions improved and it came time to try and reintroduce lake trout, the results were disappointing in all but Lake Superior where enough wild populations survived to make a decent comeback.

Species diversity is all of the different kinds of living things found in a certain habitat or ecosystem. World-wide more than 1.4 million species have been identified (Wilson, 1992) but estimates of the actual number vary from 5 million up to 100 million. Fourteen million appears to be an estimate that is commonly quoted in the literature (Global Biodiversity Assessment, 2001 Summary). Globally the estimated numbers of species are:

35,000 micro-organisms 70,000 fungi 273,000 plants 875,000 invertebrates (insects, spiders, etc.) 19,000 fish 10,500 reptiles and amphibians 9,000 birds 4,000 mammals 105,000 other animals

Ecosystem diversity is the variety of ecosystems within a landscape or region including wetlands, prairies or savannahs, lakes and rivers, forests and agricultural landscapes. The basic principles of biodiversity apply here as well but the scope is much larger. It is at this level that the interactions and links among species and the consequences of those links are evident. Less diverse ecosystems, such as coldwater streams or small lake trout lakes, contribute to the functioning and productivity of larger areas such as bioregions

Biodiversity loss:The biodiversity is under threat all over the world. Western Ghats and northeast is rich in biodiversity, they have a rich variety of vegetation as well as animals. Certain species fear a threat of decline due to day by day contracting habitats, habitat quality and hunting of some mammals. Fragmentation of habitats and the sharp decline in small subpopulations of plants and animals bring them on the edge of decline. Species already restricted to a small area are more prone to extinction according to the final technical report of the National Biodiversity Strategy and Action Plan. All the 18 domestic poultry breeds are under threat and around 40 species of plants and animals have extincted. The country has lost about 40% of its mangroves and some crucial part of its wetlands. Measures like establishing crop gene banks, seed banks and biodiversity knowledge registers are needed to curb the loss of biodiversity. Conservation:-

In-situ conservation In-situ conservation is on-site conservation or the conservation of genetic resources in natural populations of plant or animal species, such as forest genetic resources in natural populations of tree species. It is the process of protecting an endangered plant or animal species in its natural habitat, either by protecting or cleaning up the habitat itself, or by defending the species from predators. It is applied to conservation of agricultural biodiversity in agroecosystems by farmers, especially those using unconventional farming practices.

Benefits One benefit of in-situ conservation is that it maintains recovering populations in the surrounding where they have developed their distinctive properties. Another is that this strategy helps ensure the ongoing processes of evolution and adaptation within their environments. As a last resort, exsitu conservation may be used on some or all of the population, when in-situ conservation is too difficult, or impossible. Reserves Wildlife and livestock conservation is mostly based on in situ conservation. This involves the protection of wildlife habitats. Also, sufficiently large reserves are maintained to enable the target species to exist in large numbers. The population size must be sufficient to enable the necessary genetic diversity to survive within the population, so that it has a good chance of continuing to adapt and evolve over time. This reserve size can be calculated for target species by examining the population density in naturally-occurring situations. The reserves must then be protected from intrusion or destruction by man, and against other catastrophes. Agriculture In agriculture, in situ conservation techniques are an effective way to improve, maintain and use traditional or native varieties of agricultural crops. Such methodologies link the positive output of scientific research with farmers experience and field work. First, the accessions of a variety stored at a germplasm bank and those of the same variety multiplied by farmers are jointly tested in the producers field and in the laboratory, under different situations and stresses. Thus, the scientific knowledge about the production characteristics of the native varieties is enhanced. Later, the best tested accessions are crossed / mixed and multiplied under replicable situations. At last, these improved accessions are supplied to the producers. Thus, farmers are enabled to crop improved selections of their own varieties, instead of being lured to substitute their own varieties with commercial ones or to abandon their crop. This technique of conservation of agricultural biodiversity is more successful in marginal areas, where commercial varieties are not expedient, due to climate and soil fertility constraints. Or where the taste and cooking characteristics of traditional varieties compensate for their lower yields. Ex-situ conservation means literally, "off-site conservation". It is the process of protecting an endangered species of plant or animal outside of its natural habitat; for example, by removing part of the population from a threatened habitat and placing it in a new location, which may be a wild area or within the care of humans. While ex-situ conservation comprises some of the oldest and best known conservation methods, it also involves newer, sometimes controversial laboratory methods. Human care methods Zoos and botanical gardens are the most conventional methods of ex-situ conservation, all of which house whole, protected specimens for breeding and reintroduction into the wild when

necessary and possible. These facilities provide not only housing and care for specimens of endangered species, but also have an educational value. They inform the public of the threatened status of endangered species and of those factors which cause the threat, with the hope of creating public interest in stopping and reversing those factors which jeopardize a species' survival in the first place. They are the most publicly visited ex-situ conservation sites, with the WZCS (World Zoo Conservation Strategy) estimating that the 1100 organized zoos in the world receive more than 600 million visitors annually. Endangered plants may also be preserved in part through seedbanks or germplasm banks. The term seedbank sometimes refers to a cryogenic laboratory facility in which the seeds of certain species can be preserved for up to a century or more without losing their fertility. It can also be used to refer to a special type of arboretum where seeds are harvested and the crop is rotated. For plants that cannot be preserved in seedbanks, the only other option for preserving germplasm is in-vitro storage, where cuttings of plants are kept under strict conditions in glass tubes and vessels.

A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about −150 degrees Celsius). Endangered animal species are preserved using similar techniques. The genetic information needed in the future to reproduce endangered animal species can be preserved in genebanks, which consist of cryogenic facilities used to store living sperm, eggs, or embryos. The Zoological Society of San Diego has established a "Frozen zoo" to store such samples using modern cryopreservation techniques from more than 355 species, including mammals, reptiles, and birds. A potential technique for aiding in reproduction of endangered species is interspecific pregnancy, implanting embryos of an endangered species into the womb of a female of a related species, carrying it to term. It has been carried out for the Spanish Ibex. Showy Indian clover, Trifolium amoenum, is an example of a species that was thought to be extinct, but was rediscovered in 1993 by Peter Connors in the form of a single plant at a site in western Sonoma County. Connors harvested seeds and grew specimens of this critically endangered species in a controlled environment. The Wollemi Pine is another example of a plant that is being preserved via ex-situ conservation, as they are being grown in nurseries to be sold to the general public