CBSE Class 10 Science – Chapter 15: Our Environment – Detailed Notes & Explanation

• Environment is defined as the surroundings in which the organism lives.
• Environmental science is the systematic, scientific study of our environment as well as our place in it.
• This study gives us the scientific foundations to understand certain important areas of economic importance that are essential for the existence, such as agriculture, forestry and fisheries.
• This study also gives us a basis for predicting, preventing and finding remedial measures to minimize pollution. It helps us to understand the consequences of the human intervention in the natural processes, such as construction of dams on rivers, diversion of rivers, cutting of forests, etc.
• The environment may be the physical environment, the chemical environment or the biological environment.

Biosphere

A zone having land, water and air where life exists is referred to as biosphere.

or

The life supporting zone of earth, where atmosphere, lithosphere and hydrosphere meet, interact and make life possible is known as biosphere.

• The term biosphere was proposed by Eduard Suess(1875).
• Biosphere extends to about 22.5 km in thickness from ocean bottom to mountain tops. However all parts of the biosphere are not equally inhabited. Maximum density of organisms is found in tropical rain forests and coral reefs.
• The biosphere is the largest biological system. It consists of number of small functional units called ecosystems.
• A biosphere includes all living organisms and all life supporting regions of the earth. It includes not only terrestrial but the water regions as well. It comprises three regions namely, hydrosphere, lithosphere and atmosphere.
• The biosphere can be studied from lower to higher levels of organisation starting from population, biotic community, ecosystem and biome.
• A population comprises of individuals of same species. Various population constitute a biotic community.

When biotic communities and abiotic components interact with each other, an ecosystem is formed. Various ecosystems in a given geographical area form a biome.

The various components of biosphere can be discussed under the following heads :

Population

A group of individuals of the same species in a given area constitute a population. It has a definite organisation and structure and exhibits various characteristics. The population may be deemed as the starting point of higher level (supraorganismal) organisation.

Biotic Community

A group of populations of different species in a given area is referred to as biotic community. It includes several populations of plants and animals of a particular area which associate with each other e.g., a human being lives in a particular area and interacts with other members of the family. He domesticates some animals and also interacts with plants for various uses. Thus, it can be said that he is living in a biotic community.

Ecosystem

A system resulting from the integration of living and non-living components of the environment is called ecosystem.

• According to Odum (1962), “A basic functional unit of organisms and their environment, interacting with each other and with their own components is termed as ecosystem”.
• Ecosystem is a self contained structural and functional unit of biosphere which consists of distinct biotic community and the physical environment, both interacting and exchanging materials between them.
• There is a frequent exchange of energy and materials between adjoining ecosystems. It is an open system and depends upon solar energy from outside as it energy source.
• An ecosystem can be temporary (e.g., rain water, pond, lake) or permanent; natural (terrestrial-a forest, a meadow, grass land, a desert or a hillside; aquatic-a pond, a lake, a river, a sea coast and an ocean) or artificial i.e. man made (e.g., cropland (agro-ecosystem) a garden, a park, a kitchen garden, or an aquarium); small (e.g., edge of a pond, a drop of pond water) or large (e.g., ocean).

Biome

Various ecosystems combine together in a larger region to constitute a biome.

The total annual rainfall, temperature range, nature of soil, barriers, latitude and altitude determine the nature and extent of a biome. Basically a biome is the largest terrestrial community. Tundra, northern coniferous forests (taiga), deciduous forests, tropical rain forests, mediterranean scrub forests (chapparal), tropical savanah, grass land and deserts are the principal biomes of the world.

Additional Information

• The term Ecosystem was coined by Tansley. According to him Ecosystem is a symbol of structure and function of nature.
• The term Ecology was first of all described by E.Haeckel.
• Father of Indian Ecology-Prof. Ramdeo Mishra.
• The boundaries of ecosystem are indistinct and have an overlapping character with each others
• “The total group of living things and environment of factors present in a particular place is called as ecosystem.”
• It means any structural and functional unit of the environment that can be identified and studied is called as ecosystem.
• Ecosystem may be natural or artificial, permanent or temporary. Large ecosystem is called as biome such as desert, forest etc.

Ecosystem

In the biosphere, Ecosystems may be classified on the basis of:

• Aquatic Ecosystem
• Terrestrial Ecosystem

Aquatic Ecosystem:

The aquatic ecosystem refers to all such natural systems found mainly on or in the water. The nature and characteristics of all living and non-living things in the aquatic system are determined based on the environment around their ecosystem. Organisms in these ecosystems interact with different organism in aquatic and terrestrial ecosystems.

Following are the types of aquatic ecosystem:

Freshwater ecosystem: It is one of the essential ecosystems for both humans and other organisms living on land. This is because freshwater ecosystem is a source of drinking water. It also helps in providing the necessary energy and water for transportation, recreation, etc.

The freshwater ecosystem mainly includes lentic, lotic, and wetlands.

Lentic: Water bodies that are slow or present in some areas are fall under lentic. For example, ponds, lakes, pools, etc. Lakes are known as major water sources and are surrounded by the earth.

Lotic: Fast-moving water bodies Where the entire body of water moves in a definite direction are fall under the lotic. For example, streams and rivers

Wetlands: An area with long wet soil that falls under wetlands.

Marine Ecosystem: The marine environment is usually characterized by presence of salt. These ecosystems are saltier than the ecosystem of fresh water.

In addition, they are known as the largest ecosystem on Earth. It usually includes all seas and their components. In addition, the marine ecosystem has a diverse flora and fauna, which supports a much larger diversity of freshwater ecosystems. This type of ecosystem is important for both marine and terrestrial environments.

Specifically, the ecosystem includes salt marshes, lakes, coral reefs, river estuaries, estuaries, mangroves, submarines, and deep seas. The salt marshes, mangrove forests and marshes are said to be among the most productive ecosystem. Coral reefs are known for providing an adequate supply of food and shelter to many marine people around the world.

Terrestrial Ecosystem:

Following are the types of terrestrial ecosystem:

Forest Ecosystem:

A forest ecosystem is an ecosystem where many organisms live together with abiotic components. There are many kinds of plants and animals in this system of things. This usually means that the forest ecosystem has a high density of living organisms and non-living abiotic elements. The forest environment usually includes a variety of plants, microorganism, animals and other species.

Carbon sinks are much important and play a role in regulating Earth’s total temperature. Changes in the forest ecosystem affect the entire balance of the environment, and severe changes or deforestation can also kill the whole ecosystem. Forests are often subdivided into tropical rain forests, evergreen forests, temperate forests, tropical forests, and Taig.

Grassland ecosystem:

Grassland ecosystem is called those ecosystems where the number of trees is low. This ecosystem mainly includes grass, shrubs, and herbs. That means grass is the main crop in these natural areas, and legumes are often part of the hybrid family.

Grassland ecosystems are common in both tropical and subtropical regions of the world; however, they have a distinct variety. Examples of these ecosystem include savanna grasslands and cooler grasslands. It is home to a variety of grazing animals, insects and herbivores.

Mountain Ecosystem:

As the name implies, the mountainous ecosystem is dominated by mountains when the climate is generally cold and rainy. As a result of climate change, this ecosystem has a wide variety of habitats where species of animals and plants are found. The highlands have a cold and harsh climate. This is the reason why only alpine vegetation is found in these natural areas. Animals found in these natural habitats often have fur coats to protect them from the cold weather.

Besides, especially coniferous trees are found on the lower slopes of the mountains. Examples of mountain ecosystems include mountain peaks in the Arctic regions. It is covered with snow most of the year.

Desert ecosystem:

The Desert ecosystem exists worldwide and covers about 17 percent of its desert areas. These are areas where annual rainfall is usually less than 25 mm. Thanks to a few trees and sandy soil, sunlight is essential to these natural systems. That is why these natural areas have surprisingly high temperatures and low water availability. At night, however, it is very cold.

It has unique flora and fauna. Plants grow with little water and conserve the amount of water that may be present in the leaves and stems. For example, the spiny-leafed cactus is a type of desert plant with a water-retaining feature on the stem. Similarly, animals are also adapted to the desert ecosystem. Other common animals are camels, reptiles, a variety of insects and birds.

Ecosystem consists of two components:

1. Biotic component
2. Abiotic component (environment, soil etc.)

BIOTIC COMPONENTS:

Different biotic components are connected, through food chain or other relation. That is why it is said that all the living organisms comes under biotic components. Food available for biotic components can be

Biotic components are of three types which are essential for ecosystem

Producers: All the autotrophs of ecosystem are called as producers. The green plants are the main producers. Green plants absorb solar energy and convert it into chemical energy. It means energy enters into the ecosystem through the producers. The solar energy is the only ultimate source of energy in ecosystem. This energy is available to the remaining living organisms through the medium of food.

Consumers: Those organisms which consume food (eat food) prepared by producers are called consumers. The consumers depend on producers for food, directly or indirectly. The consumers get their food by eating other organisms or their products. All the animals are consumers. They are known as heterotrophs. Consumers can be further divided into three groups: herbivores, carnivores and omnivores.

1. Herbivores: Some animals eat only plants (or their products). Those animals which eat only plants are called herbivores. The herbivores may eat grasses, leaves, grains, fruits or the bark of trees. Some examples of herbivores are: Cow, Buffalo, Goat, Sheep, Horse, Deer, Camel, Ass, Ox, Elephant, Monkey, Squirrel, Rabbit and Hippopotamus. Since herbivores obtain their food directly from plants (or producers), therefore, herbivores (like Cattle, Deer, Goat, etc.) are Primary Consumers.
2. Carnivores: Some animals eat only other animals. They do not eat plant food at all. Those animals which eat only other animals as food are called carnivores. Some examples of the carnivores are: Lion, Tiger, Frog, Vulture, Kingfisher, Lizard, Wolf, Snake and Hawk. The carnivores are usually of two types (a) small carnivores and (b) large carnivores. The small carnivores which feed on herbivores (primary consumers) are called secondary consumers. For example, a grasshopper, rat, seed eating birds and frog, etc., are Secondary Consumers. The large carnivores (or top carnivores) which feed upon the small carnivores (secondary consumers) are called tertiary consumers. For example, lion, tiger, birds of prey (such as hawk) and humans (man) are some of the Tertiary Consumers.
3. Omnivores: Some animals eat both, plants as well as other animals. Those animals which eat both, plants and animals are called omnivores. Some of the examples of omnivores are: Man (Human Beings), Dog, Crow, Sparrow, Bear, Mynah and Ant.

Decomposers or Microconsumers: Those living organisms which decompose the dead bodies of producers and consumers and release mineral substances again into the soil which are present in the dead bodies. So that decomposers help in mineral cycle. Only because of this land is the main source of minerals. The main decomposers in ecosystem are – bacteria and fungi which decompose continuously dead animals and dead plants.

Importance of Decomposers: The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment. Thus, it is only due to the presence of decomposers that the various nutrient elements which were initially taken by plants from the soil, air and water are returned to the soil, air and water, after the death of plants and animals. In the absence of decomposers, the soil, air and water would not be replenished by elements from the bodies of dead organisms. Thus, the decomposers help in recycling the materials in the ecosystem so that the process of life may go on and on like an unending chain.

Scavengers : Vulture never kills any animal so that vulture is a scavenger, not a decomposer. The process of decomposition takes place outside the body of bacteria. The breakdown of the food materials takes place in the body of vulture and minerals are released into the soil in the form faecal materials. They are also called as reducers because they decomposes and remove the dead bodies of the organism.

Abiotic (Non-living) Component: These include the non-living physico-chemical factors of the environment. These components not only affect the distribution and structure of organisms but also their behaviour and inter relationships. Abiotic factors include:

1. Inorganic substances: Inorganic substances, e.g., carbon, nitrogen, oxygen, calcium, phosphorus etc. and their compounds (water, carbon dioxide, etc.) constitute the main abiotic components. These occur either in the form of compounds dissolved in water, in the soil or in free state in air.
2. Organic compounds: These include carbohydrates, proteins, lipids, nucleic acids etc. These are present in living organisms and dead organic matter. The dead organic matter is broken down by the action of decomposers (e.g., bacteria, fungi) into inorganic substances for their recycling.
3. Climatic factors: These include light, temperature, humidity, wind, rainfall, water etc. and also edaphic factors (e.g., soil, topography, minerals, pH etc.).Structure of an Ecosystem :
   • The characteristic structure of an ecosystem is obtained by the systematic physical organisation of the abiotic and biotic components of that particular ecosystem.
   • The two main structural features of any ecosystem are its ‘species composition’ and ‘stratification’.
   • An ecosystem can be represented by depicting the producers – consumers relationship in the given ecosystem.
   • This is also called the ‘Trophic structure’ of an ecosystem, wherein each animal population forms the various trophic levels.
   • The producers (green plants) always form the first trophic level. Herbivores, which feed on producers, are at the second trophic level followed by secondary consumers, tertiary consumers and so on.
   • Trophic structure of an ecosystem can be described in terms of its total amount of nutrients or the amount of living material.
   • The amount of nutrients in the soil at any given time is referred as ‘standing state’ whereas the amount of living material is referred as ‘standing crop’.
4. Functions of an Ecosystem: The main functions of an ecosystem are :Energy flow :
   • From sun to producers
   • Producers to consumers
   • Consumers to decomposers

Energy flow in an ecosystem is a key function of an ecosystem. It determines the following two laws of Thermodynamics:

(A) First law : It states, that energy can neither be created nor destroyed, but can be transferred from one form to other.

(B) Second law : It states, that every energy change involves the degradation or dissipation of energy, from concentrated to the dispersed form due to metabolic functions, so that only a small part of energy is stored in the biomass.

Productivity: Ecosystem helps to maintain the productivity, of the system. The rate of organic matter or biomass production is called as productivity. The study of biomass production in the ecosystem is called as production ecology.

Nutrient cycles: All living organisms get matter from the biosphere component i.e. lithosphere, hydrosphere and atmosphere. Essential elements or inorganic substances are provided by earth and are required by organisms for their body building and metabolism, they are known as biogeochemical or biogenetic nutrients.

Development and stabilization: This function is necessary for the development and giving stability to various life forms, by undergoing certain modifications.

Mineral cycling (Biogeochemical cycles) : The chemical elements composing the abiotic components are circulated in an ecosystem starting from nutrient pool (soil) to producers, producers to consumers, consumers to decomposers and then back to the nutrient pool.

Food Chain

The chain of organisms which involves the transfer of energy from one trophic level to the next trophic level is called a food chain.

• The flow of food or energy in an ecosystem is called a food chain. Those organisms which join with the food chain are termed as Trophic levels.
• Usually, there are four trophic levels present in the ecosystem because the level of energy decreases during the flow of energy from one trophic level to another trophic level.

1. First trophic level [T1] – Producers
2. Second trophic level [T2] – Primary consumers
3. Third trophic level [T3] – Secondary consumers
4. Fourth trophic level [T4] – Top consumers

The flow of energy occurs in an ecosystem from the first trophic level to the fourth trophic level in the food chain, There are five trophic levels also found in a highly complex ecosystem in which tertiary consumers are present in between the secondary consumers and top consumers, then fifth trophic level (T5) formed by the top consumers.

Food Chain Examples

A food chain represents a single directional transfer of energy. For example:

Food Chain in a forest

In this food chain, the grass is the producer organism that uses sunlight energy to prepare food like carbohydrates by the process of photosynthesis. This grass is then consumed by a herbivore like deer, and the deer is consumed by a carnivore like lion.

Food chain in grassland

In this food chain, grass is the producer. The insects (herbivores) are the primary consumer, the frog (small carnivore) and snakes are the secondary consumers whereas the bird (top carnivore or large carnivore) is the tertiary consumer.

Grass → Insects → Frog → Snake → Birds

Food chain in a water

The food chain operates in the aquatic ecosystem (water ecosystem) like a pond, lake, or sea (ocean).

In this aquatic food chain, Phytoplankton algal is the producer. The Zooplankton is the primary consumer, small fish is the secondary consumer. And bigger fish is the tertiary consumer.

Types of Food Chain

There are three types of food chains which are found in nature.

• Predator food chain
• Parasitic food chain
• Saprophytic food chain

Predator food chain extends from producers through herbivores to carnivores, parasitic food chain starts from producers but ends with parasites and saprophytic food chain starts with decomposers. Producers are autotrophic organisms which synthesize organic food from simple inorganic raw material through photosynthesis by utilizing solar energy. A part of food synthesized by the producers is used in their body building, while the rest is utilized in providing energy for various life activities.

• Some common predator food chains are given below:
• Vegetation → Grasshoppers → Shrew → Hawk
• Vegetation → Rabbit → Wolf →Tiger
• Vegetation → Frog → Snake → Peacock
• Plant → Rat → Snake → Hawk.

Aquatic food chains

• Phytoplanktons→ Zooplanktons → Small crustacians→ Predator insect → Small fish → Large fish → Crocodile
• Phytoplanktons→ Zooplanktons → Small fish → Large fish → Shark
• Phytoplanktons→ Zooplanktons → Fish → Crane → Hawk.

Trophic Level:

Each step or level of the food chain forms a trophic level.

• The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers.
• The herbivores or the primary consumers come at the second trophic level.
• The small carnivores or the secondary consumers are at the third trophic level.
• The larger carnivores or the tertiary consumer form the fourth trophic level.

Food chain operating in the grassland, which is:

Grass → Insects → Frog → Birds

In this food chain, grass represents the 1st trophic level; insect represents the 2nd trophic level; frog represents the 3rd trophic level, whereas bird represents 4th trophic level.

Food Web:

A food web(or food cycle) depicts feeding connections (what eats what) in an ecological community and hence is also referred to as a consumer-resource system.

Ecologists can broadly lump all life forms into one of two categories called trophic levels:

1. The autotrophs, and
2. The heterotrophs.

• To maintain their bodies, grow, develop, and to reproduce, autotrophs produce organic matter from inorganic substances, including both minerals and gases such as carbon dioxide.
• These chemical reactions require energy, which mainly comes from the sun and largely by photosynthesis, although a very small amount comes from hydrothermal vents and hot springs.
• A gradient exists between trophic levels running from complete autotrophs that obtain their sole source of carbon from the atmosphere, to mixotrophs(such as carnivorous plants) that are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete heterotrophs that must feed to obtain organic matter.
• The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs.
• The food web is a simplified illustration of the various methods of feeding that links an ecosystem into a unified system of exchange.
• There are different kinds of feeding relations that can be roughly divided into herbivory, carnivory, scavenging and parasitism. Some of the organic matter eaten by heterotrophs, such as sugars, provides energy.
• Autotrophs and heterotrophs come in all sizes, from microscopic to many tonnes- from cyanobacteria to giant redwoods, and from viruses and bdellovibrio to blue whales.

Characteristics Of A Food Web:

1. Unlike food chains, food webs are never straight. Instead, each food web is formed by interlinking of food chains.
2. A food web provides alternative pathways of food availability. For example, if a particular species of producer is destroyed by a disease in the ecosystem, the herbivores of that area can feed on other species of producers. Similarly, Secondary consumers (e.g., predatory birds) may feed on rats or mice in the event of decrease in population of rabbits in that area on which they also commonly feed.
3. Greater alternatives available in a food web make the ecosystem more stable.
4. Food webs also help in checking the overpopulation of highly fecundive species of plants and animals.
5. Food webs also help in ecosystem development.

Difference Between Food Chain And Food Web:

Food chain	Food web
Food chain is the straight single path of transfer of food energy in the ecosystem	It consists of a number of inter−connected food chains through which food energy is passed in the ecosystem
Members of higher trophic level feed upon a single type of organisms of lower trophic level.	Members of higher trophic level can feed as a number of alternative organisms of the lower trophic level.
It does not have any effect on improving the adaptability or stability of the ecosystem.	Presence of food web increases the stability of the ecosystem

Ecological Pyramids

An ecological pyramid is a graphical representation of an ecological parameter like number of individuals or amount of biomass or amount of energy present in various trophic levels of a food chain with producers forming the base and top carnivores from the tip. Ecological pyramids could be upright, inversed or spindle shaped. There are three important parameters of each trophic level in a food chain i.e. number of individuals, amount of biomass and amount of energy.

Pyramid of Number: In this type of pyramid the number of individual organisms in various trophic levels is shown. These pyramids may be upright or inverted. The number of organisms of any trophic level depends upon the availability of organisms which are used as food on lower level so that availability of food is the main factor. These producers are of two types:

(i) Phytoplanktons: They are the inactive floating plants, because they do not have locomotory organs e.g. Diatoms.

(ii) Phytonektons: These plants swim actively in water, because in them locomotory organs are present. Usually flagella are present in these plants. e.g. Chlamydomonas and dinoflagellates. The number of phytoplanktons and phytonektons are higher per unit area of water because they are unicellular.

In a tree ecosystem the pyramid of number is inverted. This is called as parasitic ecosystem because birds depend upon tree and parasites depend upon birds. Therefore with the increase in the number of trophic levels, the number of the organisms increases sequentially.

• Pyramid of number shows biotic potential of an ecosystem.
• The number of members of any particular species in a favourable condition is called as their biotic potential.
• When the number of the members of any species increases then it is called as population explosion.

Pyramid of Biomass:

The biomass of each trophic level is shown by this pyramid. Mostly these pyramids are also upright (erect). e.g. Tree ecosystem.

• Pyramid of biomass in aquatic ecosystem is inverted, because in this producers are micro organisms and their biomass is lesser than other trophic levels.
• Pyramids of biomass show the standing crop of ecosystem. It means total amount of living matter at a particular time in an ecosystem is called as standing crop.
• Total amount of nonliving matter in an ecosystem is called as standing state.

Pyramid of Energy :

It always remains erect, because flow of energy is not cyclic. i.e. during the flow of energy at each trophic level goes on decreasing.

Biodiversity :

Biodiversity represents the variety and variability of all animals, plants and organisms.

The term biological diversity or refers to the variety of life forms and habitats found in a defined area. Biodiversity can be defined “as the variety and variability of all animals, plants and micro­organisms and the ecological complexes of which they are a part”.

Diversity characterizes most living organisms, the our earth supports something like 5 to 10 million species of plants and animals (IUCN, 1980) which have been the result of 3 billion years of evolution involving mutation, recombination and natural selection.

Levels Or Components Or Form Of Biodiversity :

Biodiversity is said ions in the sequence of four base pairs in DNA.

Ecosystem: Indian ecosystem diversity is described at each of the three levels (biogeographical region, biotic province and biome). Largest of identified ecosystems has been the biogeographical zone. The vast area covered by biogeographical zone contains a wide diversity of smaller units called biotic provinces. Finally, within each biotic province, various kinds of biomes are distinguished. Biome classification broadly follows commonly used terminology distinguishing between forests, grasslands, wetlands, deserts and other such ecosystem on the basis of their physical appearance and dominant biotic or biotic element.

Species: Species are the most commonly used unit describing biodiversity. Comparisons of the diversity found in different countries or ecosystems, for instance, are almost always based on species number. According to investigations into Amazonian rainforest canopy (Wilson, 1988), worldwide, some 5 to 30 million species are believed to exist. Nearly 1.7 million have so far been described (Myers, 1993). Species diversity has frequently been used as an indicator of the conservation significance of an area.

Genes: The genetic diversity within a species is expressed by many terms, subspecies, breeds, races, varieties and forms. This diversity arises from ‘‘variations in the sequence of four base pairs in DNA’’  

Present Status Of Biodiversity

India is one of the 12 megadiversity countries of the world for its great diversity of plant life, especially the angiosperms.

India’s biological diversity is one of the most significant in the world. About 48,000 species of plants (about 11% of worlds flora) and 81,000 species of animals (about 6.4% of world’s fauna) are estimated to occur in the country.

The floral diversity includes about 17,000 species of angiosperms; 64 of gymnosperms, 1022 of pteridophytes, 2,843 of bryophytes, 1,940 of lichens, 13,000 of fungi and 12,480 of algae. While about 35% of the flowering plants and about 18% of the total flora is endemic to the country, the endemism amongst the animals is as high as 62% in groups like amphibia.

Some of the biological rich areas of India are either unexplored or under-explored, the recorded biodiversity may be first only a part of the biological wealth that might actually exist.

Range of diversity in plants and animals genetic resources is highly significant. The Indian subcontinent is known as “Hindustan Centre” – one of the 12 centres of origin and diversity of crop plants.

About 166 species of domesticated agri-horticultural crop plants, and over 320 species of wild progenitors of these, occur in India. This rich diversity of living resources notwithstanding, about 10% of the country’s recorded higher group of plants and a large segment of its wild fauna today belong to different “Red data” categories.

• Expansion of industry and agriculture on prime forest lands.
• Urbanisation and large scale developmental projects.
• Pollution.
• Overutilisation of biological resources.

Living Resources Conservation Has Three Specific Objectives

To maintain essential ecological processes and life support system.

To preserve biological diversity.

To ensure that any utilisation of species and ecosystems is sustainable.

Conservation Of Bio-diversity

There is an urgent need to arrest species extinction. Equally important is the need to prevent the loss of thousands of years of human selection in crop species and domesticated animals for posterity.

In-situ Conservation

In-situ conservation measures are primarily related to the natural, biodiversity within the evolutionary dynamic ecosystems of the original habitat or natural environment. It is the best, easiest, most advantageous, besides being most feasible method to conserve biological diversity.

In-situ conservation includes a comprehensive system of protective areas. These include National parks, Sanctuaries, Nature Reserves, Natural Monuments, Cultural Landscapes, Biosphere reserves and several others.

Geography and Biodiversity

Strong equations have been suggested between various geographical factors and the extent of biodiversity. For instance, as a general rule, the larger the size of an area, the greater the number of species found in it. Indeed, even in the case of the population of a single species, a larger spread is more likely to lead to diverse adaptations among different populations and thereby to speciation.

This is one overwhelming justification for larger-sized conservation areas though of course it is also true that a number of smaller protected areas in more diverse areas could help to conserve a larger biodiversity Other geographical variables include latitude, elevation, and precipitation. Elevation is inversely related, with higher diversities found at lower heights, and very poor diversity at the upper extreme of altitude.

Ex-situ Conservation

Ex-situ conservation is conservation outside their habitats by perpetuating sample population in genetic resource centres, zoos, botanical gardens, culture collections etc., or in the form of gene pools and gamete storage for fish, germplasm banks for seeds, pollen, semen, ova, cells etc.

Plants are more readily maintained than animals, yet zoos have recorded success with captive breeding of animals. e.g., the Pere David’s Deer and the European Bison have lost their wild habitats many decades ago, have been kept alive solely through zoos and similar facilities.

Ex-situ conservation measures for restoration of biodiversity should aim at consolidating the public network of zoological parks and botanical gardens, herbaria, aquaria, gene/seed/embryo banks, in-vitro and cryopreservation facilities.

Ozone Layer And Its Depletion

The global environment is basically formed by three parts – atmosphere, hydrosphere and lithosphere. The atmosphere extends over about 600 km from the earth’s surface. Four layers of atmosphere are – troposphere, stratosphere, mesosphere and thermosphere.

Ozone layer, commonly called ozone blanket, comprises of high concentration of ozone about 18-26 km above in the stratosphere. As per estimates, 90% of the total atmospheric ozone is present in this region.

Formation of ozone:

Ozone is a form of oxygen. Ozone (O₃) is a molecule formed by three atoms of oxygen. While O₂, which we normally refer to as oxygen, is essential for all aerobic forms of life. Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen (O₂) molecule. The higher energy UV radiations split apart some molecular oxygen (O₂) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone.

Function of ozone:

Ozone is a poisonous gas but is not stable nearer to earth’s surface. It performs an essential function where it is found. It absorbs the harmful radiations from the Sun. It shields the surface of the earth from the ultraviolet (UV) radiation of the sun. Absorption of UV radiations by ozone blanket is proportional to its thickness.

Ozone Layer Depletion:

The decline in spring – layer thickness is called ozone hole. Ozone hole is largest over Antarctica and was just short of 27 million sq. km. during September 2003. Main chemicals to be responsible for destruction of ozone-layer are: chlorofluorocarbons (CFCs), halogens (used in fire extinguishers), methane and nitrous oxide. Out of these, most damaging is the effect of CFCs which are a group of synthetic chemicals and are used as coolants in refrigerators and air conditioners; as cleaning solvents, propellants and sterilant etc. These CFCs produce “active chlorine” in the presence of UV-radiations. These active chlorine radicals catalytically destroy ozone and convert it into oxygen.

Effects of Ozone Layer Depletion :The thinning of ozone layer results in increase in the UV radiations (in the range of 290 – 320 nm) reaching the earth’s surface. It is estimated that 5 percent loss of ozone results in 10 per cent increase in UV – radiations. These UV – radiations can:

(i) Increase in incidences of cataract and skin cancer.

(ii) Decrease in the functioning of immune system.

(iii) Inhibit photosynthesis in most of phytoplanktons so adversely affecting the food chains of aquatic ecosystems.

(iv) Damage nucleic acids of the living organisms.

Saving the ozone layer:

The thinning of ozone layer started in 1980s. In 1987, the United Nations Environment Programme  (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.

What are Our Environment ?

• Environment is everything that is around us which includes both biotic and abiotic components.
• Abiotic components are the non-living components i.e., the physical factors like temperature, light, wind, water, humidity, soil, minerals, etc.
• The biotic components are the living organisms like plants, animals, human beings etc. Both biotic and abiotic components interact with each other to form the environment as a whole.
• An ecosystem includes all living organisms along with the abiotic components which interact with each other to maintain a balance in the nature.
• The term ecosystem was introduced by Tansley in 1935.

• Producers are mainly autotrophs.
• Consumers cannot prepare their own food. They depend on autotrophs directly or indirectly for food. They are primary consumers [which eat plants or plants products], secondary consumers. [Feed upon primary consumers], tertiary consumers [feed upon secondary consumers], quaternary consumers [feed upon tertiary consumers and are at the top most level of food chain].
• Decomposers like bacteria, fungi etc., feed upon the decay of dead producers and consumers.
• The transfer of food energy from plant sources through a series of organisms in an ecosystem is known as food chain.
• The interlinking sequence starting from an autotroph to herbivores, carnivores and top most level consumers is called a food chain.

• A food chain shows one path how energy in form of food flows from producers to consumers.
• A food web shows many paths i.e., it is a network of food chains where an organism eats several types of organisms or eaten by many different organisms.

• The distinct sequential steps in the food chain where transfer of energy occurs are referred to as different trophic level, which is represented as under.

• Energy flow in an ecosystem is unidirectional i.e., it flows from autotrophs to herbivores to secondary consumers, tertiary consumers in one direction.
• At each trophic level some amount of energy is lost. Lindeman suggested a Ten percent rule which states that the rate of transfer of energy from one trophic level to the next trophic level is of the order of 10%.
• For example if energy produced by a green plant is 100 calories only 10 calories is available to herbivores then 1 calorie to secondary consumers and very less energy i.e., 0.1 calorie to tertiary consumers. So at each trophic level the energy goes on decreasing hence a food chain or food web consists of 3-4 levels or maximum 5.
• Biomagnification is the process which involves the progressive increase in the concentration of toxic or harmful substances at different trophic levels. So the organisms that are at the top of food chain have accumulated a maximum concentration of harmful chemicals in their body. Example : Accumulation of pesticides like DDT.

• Ozone layer prevents the harmful UV rays of sun from entering to the earth’s surface.
• CFCs which is the main cause of depletion of ozone layer and is found mainly in aerosol sprayers, refrigerators, air-conditioners etc.
• The depleting ozone layer has many harmful consequences like it causes cancer, causes genetic variations due to mutation, damages our eyes, decline of photosynthesis rate in plants.
• The first ozone hole was discovered over Antarctica.

1. Ecosystem: It is the structural and functional unit of biosphere which comprises of both biotic and abiotic components that interact with each other to form a stable and self-supporting system.	6. Food chain: The sequential interlinking of organisms involving transfer of food energy starting with a producer through a series of organisms
2. Natural ecosystem: The ecosystems which operate themselves in nature without any interference of human beings are called natural ecosystems.	7. Trophic levels: The distinct sequential steps in the food chain where transfer of energy occurs are referred to as trophic levels.
3. Artificial ecosystem: The ecosystem which is maintained by human beings like croplands, aquarium etc. is called artificial ecosystem.	8. Food web: A network of food chains which are interconnected at various trophic levels to form a number of feeding connections among different organisms is called a food web.
4. Abiotic components: The non-living physio-chemical factors like soil, humidity, sunlight, rainfall, temperature etc. are the abiotic components.	9. Biodegradable wastes: The wastes which get degraded in a natural process by the action of microbes into simpler forms are called biodegradable wastes. Example, food waste, human waste, paper waste, manure, sewage etc.
5. Biotic components: The living organisms like autotrophs, heterotrophs form the biotic components.	10. Non-biodegradable wastes: The wastes which cannot be degraded by the action of microbes in a natural way and they persist in environment for a longer period of time are called non-biodegradable wastes. Examples, Glass, metal, batteries, plastic bottles, tetra packs.