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Chapter 15

ENVIRONMENT

Our Environment is our immediate surroundings. It is composed of both Biotic

and Abiotic components which interact with each other. Different materials are

cycled in the environment in separate biological cycles to maintain the

environment.

In these cycles essential nutrients like nitrogen, carbon, oxygen, and water are

changed from one form to the other.

But man is destroying the balance in the environment today. In our daily

activities, we generate a lot of waste materials. We dump them in to the

environment. Some of these wastes breakdown and decompose without harmingthe environment. They are called Biodegradable substances. But there are also

substances which do not decompose. They are called Non-Biodegradable

substances. They remain in the environment for a long time and cause harm to

the environment.

Bio degradable Non-Biodegradable

It can be broken down in to harmlesssubstances by the action of

microorganisms like bacteria.

Eg. Kitchen waste, waste papers, leaves,

flowers, new kind of plastics made out

of polymers of carbohydrates and

proteins.

They cannot be broken down in toharmless substances by biological

process.

Eg. DDT, polythene bags, soft drink

cans, radioactive pollutants.

Impact: they do not pollute the

environment unless their volume is too

large.

Impact: they cause major pollution

They persist in the environment for

long time and harm the members of theecosystem.

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Ecosystem

An ecosystem is composed of living organisms in area with nonliving

constituents. That is, it consists of Biotic components comprising living organisms

and abiotic component factors like temperature, rain fall, wind, soil, minerals etc.

for example a garden, pond, grass land.

The organisms in an ecosystem can be classified as producers, consumers and

decomposers.

All green plants, algae etc can produce food by photosynthesis. Hence they are

called producers.

All those organisms which depend on producers directly or indirectly for their

food are called consumers.

Consumers can be classified as herbivores, carnivores, and omnivores etc.

The ecosystem has another important group called decomposers.

Decomposers comprise of microorganisms, bacteria, and fungi etc. which help to

breakdown dead remains and waste products of organisms in to simple inorganic

substances. These inorganic substances settle down in the soil and become

nutrients for the pants.

Ecosystem

Biotic components

Producers Consumers

Herbivores

Carnivores

Omnivores

Parasites

Decomposers

Abiotic components

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FOOD CHAIN:

A series of organisms belonging to different trophic levels where one organism

forms the food of another is called food chain.

Pants Deer Lion.

The first member of the series is always green plants or algae which actively

prepare food by photosynthesis.

The food products are then transferred to the next member who feed on them.

This group is called herbivore.

The third level includes animals which feed on the herbivores. That is, they arecarnivores.

The fourth level includes larger carnivores. In all these cases food acts like energy.

Thus in an ecosystem interaction of various components involves flow of energy

from one component to another. This energy supports all activities of the living

world.

The flow of energy starts from autotrophs which absorb and convert solar energy

in to chemical energy.

The chemical energy is then transferred to the trophic levels below it. In this

process only 10% of the energy is transferred to the next level.

The remaining energy is lost to the environment. The energy lost to the

environment will be in unusable form.

Thus, in an ecosystem green plants will manufacture the food and are called

producers.

In a food web, each organism will form the food for 2 or more members

belonging to different levels, so instead of straight line, the members which form

food will form a web. This is known as food web.

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.

Transfer of energy through an ecosystem. At each trophic level only a small

proportion of energy (approximately 10 percent) is transferred to the next level.

Main concept of energy flow through food chain:

1. Flow of energy is unidirectional that is the energy that is captured byautotrophs doesnt revert back to solar input and the energy which

passes to the next level, it is no longer available to the previous level.

Amount of energy goes on decreasing.

2. Since little energy is available to the next level of consumers, the foodchain generally consists of only 3 or 4 steps. The loss of energy at eachstep is so great that very little useable energy remains after 4 trophic

levels.

3. There are generally greater numbers of individuals at the lower trophiclevels of an eco system; the greatest number is of the producers.

4. Some harmful chemicals enter our bodies through food chain .Amount ofchemicals go on increasing.

Biological Magnification:

These days, due to various human activities, some harmful chemicals enter our bodies through

food chain. These chemicals come in the form of pesticides, fertilizers, etc. chemicals are

washed in to the soil and from the soil they are absorbed by the plants which are the4n

transferred progressively. Some of the chemicals are not degradable. As such they get

accumulated progressively at each trophic level. The maximum concentration of these

chemicals is collected at the top trophic level (Human bodies). This phenomenon is known as

Biological magnification.

1% of the sunlight is captured by the

leaves & 99% of energy will be lost to

the environment.

10% of energy is made available for

next trophic level &90% lost to the

environment .

10% of energy is made available for

next trophic level &90% lost to the

environment .

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Environmental problems:

1. Depletion of Ozone layer.

2. Waste disposal.

Ozone layer and its depletion:

Role of ozone layer :

Ozone is formed by three atoms of oxygen.

Ozone is formed at higher levels. UV radiation split apart oxygen molecules in to

free oxygen atoms. These atoms then combine with molecular oxygen to formozone.

O2+UV----- O+ O ; O+O2 ------ O3

It is a deadly poison at lower level but at the higher level of atmosphere, ozone

filters the ultraviolet radiation from the sun. Thus, ozone protects us from

UVradiation which would otherwise cause skin cancer in human beings.

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These days chemicals like Chloro Fluoro Carbons (CFC) which are used

as refrigerants and fire extinguishers, aerosols in shaving gels, sprays

deplete ozone layer.

Controlling measures:

1. By reducing the use of CFCs. Many countries have already banned the use of

CFCs.

2. By developing some substitutes to replace CFCs which are ozone friendly.

Waste disposal and its management:

A lot of waste material is generated by human beings in their daily activities which

pollute the soil, water and air.

Reasons for generation of large volumes of waste:

1. Changed /improved life style.2. Change in ones attitude with use of .more and more disposable items.3. Changes in packaging methods.

Modes of waste disposal:

1. More and more use of non disposable things/ biodegradable substances2. Sorting domestic waste in to biodegradable and non biodegradable items

before disposal.

3. Recycling4. Preparation of compost.