Question 1 What are the materials that remain unchanged over long periods of time? Solution
ilk packets, empty cartons, empty medicine bottles/ strips/ bubble packs and broken footwear remain unchanged for a long time. Question 2 What are the materials which change the form and structure over time? Solution
Spoil food, vegetables peels, used tea leaves, empty cartons, old and torn clothes change their form and structure over time.
Question 3 Of these materials that are changed which once change the fastest? Solution
Vegetables peels change fastest.
Question 4 Why are some substances biodegradable and some non – biodegradable? Solution
Some substances can be acted upon by the microorganism and broken down into simple substances. Such substances are called biodegradable.
Some substances are inert and cannot upon by the microorganisms and do not breakdown into simple substances. Such substances are called non – biodegradable.
Question 5 Give any two ways in which biodegradable substances would affect the environment. Solution
Biodegradable substances affect the environment in the following ways:
(i) These substances are decomposed by the action of microorganisms. This causes fowl smell.
(ii) During the process of decaying of biodegradable substances, various types of gases are released which cause air pollution.
Question 6 Give any two ways in which non biodegradable substances would affect the environment. Solution
The non – biodegradable substances affect environment in the following ways:
(i) they persist in the environment for a long time and thus damage the environment.
(ii) Such substances cause land pollution and water pollution. Question 7 What are the trophic levels? Give an example of a food chain and state the different trophic level in it. Solution
There are various series of organisms feeding of one another. These series of organisms taking part in various biotic level form food chain. the steps or levels of the food chain are called trophic levels.
An example of food chain:
Grass → Deer → Lion.
Various trophic levels are:
(i) First trophic level is grass. It is producer.
(ii) Second trophic level is deer. It is primary consumer (or herbivores).
(iii) Third trophic level is lion. It is larger carnivores. Question 8 What is the role of decomposers in the ecosystem? Solution
Decomposers are called natural cleaning agent. They act on biodegradable substances and break them into simple substances. In this way, decomposers create a balance in the environment and play an important role in the environment. Question 9 What is ozone and how does it affect any ecosystem? Solution Ozone is a molecule formed by three atoms of oxygen. Ozone is formed by the reaction of three molecules of oxygen in presence of ultraviolet (UV) rays.
Ozone performs an essential function. It shields the surface of the earth from ultraviolet radiation of the sun. If this radiation enters in the atmosphere, it could cause various disorders. So, ozone protects the ecosystem from damaging. Question 10 How can you help in reducing the problem of waste disposal? Give any two methods. Solution
(i) There are two types of wastes; biodegradable and non – biodegradable. We should use more and more substances that leave biodegradable wastes.
(ii) Biodegradable wastes are converted into manure. Non – biodegradable wastes should be sent to the factories for recycling. Question 11 What will happen if we kill all the organisms in one trophic level? Solution
Each and every trophic level depends for its energy needs on its previous trophic level. If all organisms of any of the trophic levels in a food chain are damages, the organisms of other trophic levels will also be destroyed because energy flow is stopped from one trophic level to other trophic level. Question 12 Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem? Solution
No, the impact of removing all the organisms in a trophic level is same for different trophic levels. the removal of organisms of any trophic level is damaging and it causes various disorder in ecosystem. Question 13 What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem? Solution
When any harmful chemical like DDT enters in a food chain, its concen – tration increases gradually at each trophic level. This phenomenon is called biological magnification.
The levels of this magnification will be different at different levels of the ecosystem. Question 14 What are the problems caused by the non – biodegradable wastes that we generate? Solution
The non – biodegradable wastes persist in the environment for a long time and cause various problems. Non – biodegradable wastes cause:
(i) water pollution so that water becomes unfit for drinking.
(ii) They cause land pollution and due to it land loses its beauty.
(iii) They cause stoppage of flow of water in drain.
(iv) They also cause air pollution and make the air poisonous. Question 15 If all the waste we generate is biodegradable, will this have no impact on the environment? Solution
The biodegradable wastes do not persist for a long time in the environment. However, they also cause harmful effects but these effects are only for some time. These wastes can be converted into useful substances and broken into simple substances by the action of microorganism. So, there will be impact of biodegradable waste but for a short time. Question 16 Why is the damage to the ozone layer a cause for concern? What steps are being taken to limit this damage? Solution
Enlargement of ozone hole will cause more ultraviolet rays to reach on the earth’s surface. This is very harmful for us, animals and microorganisms in the following ways:
(i) Ultraviolet radiations may cause skin disease, especially skin cancer.
(ii) Plant life will be disturbed due to retarded growth and destruction of pigments.
(iii) UV – rays may kill microorganisms, decomposers and other useful microbes. It may lead to ecological imbalance.
Steps to prevent damage of ozone layer:
(i) Judicious use of aerosol sprays propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
(ii) Limited use of supersonic plains.
(iii) Control over large scale nuclear explosions.
Question 17 What are the structural components of an ecosystem? Solution
An ecosystem consists of a non – living environment and a living biological community.
The non – living environment of an ecosystem consists of the componenets like water, carbon dioxide, oxygen, nitrogen, phosphorus and the other elements.
The living community is made up of plants, animals.
Question 18 What will happen to grass – lands if all the grazers are removed from there? Solution
If all the grazers are removed from grass lands, grass will grow unchecked. It may help the growth of some organisms harmful to the animals. Further the animals which feed on the grazers will die of starvation. Biogeochemical cycle will stop, and ultimately whole biosphere will get disturbed. Question 19 Suggest some methods of safe disposal of wastes. Solution
(i) The waste should be classified into biodegradable and non-biodegradable.
(ii) Biodegradable wastes should be converted into manure.
(iii) Non-biodegradable waste should be sent in the factories for recycling.
(iv) Plastics should be melt and mixed with asphalt to make road surface.
(v) Garbage should be thrown away in the land fill areas. Question 20 Give some examples of terrestrial and aquatic ecosystems. Solution
(i) Terrestrial ecosystem: A natural forest, a crop field, etc.
(ii) Aquatic ecosystem: A pond, a lake and an aquarium. Question 21 Describe the structure of an ecosystem. Solution
An ecosystem consists of a non – living (a biotic) environment and a living (biotic) biological community.
The non – living environment of an ecosystem consists of the components like water, carbon dioxide, oxygen, nitrogen, phosphorus and other elements.
The living community is made up of plants, animals. Question 22 How the biotic components further are categorized? Solution
The biotic component of an eco – system includes the following three types of organisms:
(i) Producers: The organisms that make their own food are called producers. All green plants are producers. Producers are also called as autotrophy.
(ii) Consumers: Consumers are the organisms that cannot make food of their own and depend upon others for the same. All animals are consumers. Consumers are also termed as heterotrophy.
(iii) Decomposers: Decomposers are the organisms that decompose the dead remains of plants and animals. decomposers are also termed as saprotrophs. Question 23 Give two examples each of producers, consumers and decomposers. Solution Producers: green plants such as sugarcane plant, wheat plant, etc.
Consumers: Animals such as cow, goat, etc.
Decomposers: certain bacteria and fungi are decomposers.
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