Our environment

Key learning



1) Our environment is composed of various biotic and abiotic factors which

interact with each other.

2) Human activities have a great impact on the functioning of the environment.

3) The wastes generated by the various human activities may be biodegradable

or non- biodegradable.

4) The enzymes present in the body of decomposers are capable of breaking

down the biodegradable substances, but not the non- biodegradable

materials.

5) The non-biodegradable materials like plastic and synthetic pesticides persist

in the environment for a long duration and may harm its biotic factors.

6) In an ecosystem, the abiotic and biotic factors interact to form a stable unit.

7) The size of an ecosystem ranges in size from as small as a pond or a

backyard garden to as large as an entire rain forest.

8) An ecosystem may be natural (like lakes and forests) or artificial (like cropfields

and aquarium).

9) The biotic factors may be classified as producers, consumers and

decomposers depending on their mode of nutrition.

10) The food manufactured by the producers from simple inorganic substances is

utilized directly or indirectly by the consumers.

11) Herbivores, carnivores, omnivores and parasites are the various types of

consumers.

12) The decomposers break down the dead bodies and wastes of organisms and

help in nutrient recycling.

13) Food chains are present in every ecosystem. Each food chain is composed of

three to five trophic levels.

14) There is flow of energy between the various trophic levels.

15) Producers convert solar energy into chemical energy, which is then utilized

by the consumers and decomposers.

16) About 1% of solar energy falling on leaves is utilized by plants in

photosynthesis to produce food.

17) A large amount of energy loss occurs when the organisms of the higher

trophic level feeds on the lower trophic level organisms.

18) There is only 10% flow of energy from one trophic level to the next higher

level. Due to this energy loss, only 4 or 5 trophic levels are present in each

food chain.

19) The number of individuals in a trophic level decreases as we go up the food

chain.

20) Food webs, consisting of several interconnected food chains, are more

common in mature.

21) Flow of energy is unidirectional and cannot be utilized by the previous trophic

levels.

22) The non-biodegradable chemicals like pesticides and insecticides enter the

food chains in land and aquatic ecosystems and then accumulate

progressively at each trophic level. This is known as biological magnification.

23) Human activities can cause several environmental problems like ozone layer

depletion and waste disposal.

24) Ozone, composed of three oxygen atoms, is a toxic chemical. It is formed by

the combination of free oxygen atom with molecular oxygen.

25) The atmospheric ozone layer prevents the entry of solar ultraviolet rays and

thus protects all organisms on Earth.

26) Use of chemicals like chlorofluorocarbons has greatly depleted the

atmospheric ozone layer, which could endanger the environment.

27) The disposal of large amounts of garbage produced in any human settlement,

especially in cities and towns is causing major environmental problems.

28) Changes in our lifestyle and attitude have created many disposable items,

many of which are non-biodegradable.

29) Effective methods of waste disposal should be found in order to reduce the

harmful effects on our environment.