This chapter highlights the impact of human activities on the environment. It explains the structure and function of ecosystems, including producers, consumers, and decomposers. Students learn about food chains, food webs, and the flow of energy in an ecosystem.

The chapter also discusses environmental issues such as pollution, waste generation, and the harmful effects of non-biodegradable substances. It emphasizes the importance of sustainable living and the need to protect our environment for future generations.

Class 10 Science Ch 15 Our Environment – Textbook

Page Number: 260

Question 1
What are trophic levels ? Give an example of food chain and state the different trophic levels in it.
Answer:
Trophic Levels : The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.
Example : A food chain operating in a grassland is given below :
Grass → Insects → Frog → Birds
NCERT Solutions for Class 10 Science Chapter 15 Our Environment Intext Questions Page 260 Q1
In this food chain

  1. Grass represents first trophic level.
  2. Grasshopper represents second trophic level.
  3. Frog represents third trophic level.
  4. Eagle represents fourth tropic level.

Question 2
What is the role of decomposers in the ecosystem ?
Answer:
(i) Decomposers help in decomposing the dead bodies of plants and animals and hence act as cleansing agents of the environment.
(ii) Decomposers also help in putting back the various elements of which dead plants and animals are made, back into the soil, air and water for reuse by the producers like crop plants.
(iii) They help in recycling of the nutrients.
(iv) They decompose dead remains thereby providing space for new life to settle in the biosphere.

Page Number: 262

Question 1
Why are some substances biodegradable and some non-biodegradable ?
Answer:
The microorganism like bacteria and other decomposer organisms (called saprophytes) present in our environment are specific in their action. They break down the materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable, whereas others are non-biodegradable.

Question 2
Give any two ways in which biodegradable substances would affect the environment.
Answer:
(i) Biodegradable substances are decomposed by the action of microorganisms and decomposed materials are recycled through geo-chemical cycle.
(ii) These substances keep the environment clean.

Question 3
Give any two ways in which non-biodegradable substances would effect the environment.
Answer:
(i) They cause air, water and soil pollution.
(ii) They may cause bio-magnification in the food chain and end up in humans.

Page Number: 264

Question 1
What is ozone and how does it affect any ecosystem ?
Answer:
Ozone (O3) is an isotope of oxygen, i.e., it is a molecule formed by three atoms of oxygen.
At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organisms. Ultraviolet rays can cause skin cancer.

Question 2
How can you help in reducing the problem of waste disposal ? Give any two methods.
Answer:
(i) Recycling : The solid wastes like paper, plastics and metals, etc. are recycled.
(ii) Preparation of Compost: Biodegradable domestic wastes such as left over food, fruit and vegetable peels and leaves of potted plants, etc. can be converted into compost by burying in a pit dug into ground.

NCERT Solutions for Class 10 Science Chapter 15 Textbook Chapter End Questions

Question 1
Which of the following groups contain only biodegradable item ?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit peels, cake and lime juice
(d) Cake, wood and grass
Answer:
(a) Grass, flowers and leather.

Question 2
Which of the following constitutes a food-chain ?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Grass, goat and human.

Question 3
Which of the following are environment friendly practices ?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop on her scooter
(d) All of the above
Answer:
(d) All of the above.

Question 4
What will happen if we kill all the organisms in one trophic level ?
Answer:
The food chain would end and ecological balance would be affected.

  1. If the herbivores are killed, then the carnivores would not be able to get food and would die.
  2. If carnivores are killed, then the population of herbivores would increase to unsustainable level.
  3. If producers are killed, then the nutrient cycle in that area would not be completed.

Question 5
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 ?
Answer:
Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, on removing producers; herbivores would not be able to survive or they would migrate and ecosystem would collapse. If herbivores are removed, producers would grow unchecked and carnivores would not get food. If carnivores are removed, herbivores would increase to unsustainable levels and could destroy the producers. If decomposers are removed, the dead animals would pile up due to which the environment would become polluted.

In addition to this, if dead animals will not decompose, the recycling of nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the balance of the ecosystem the presence of organisms is necessary at each trophic level.

Question 6
What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ?
Answer:
Biological magnification : The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification.
Yes, levels of bio-magnification would increase as the trophic level increases and would be the highest for topmost trophic level. It would affect their biological process such as growth, reproduction, etc.

Question 7
What are the problems caused by the non-biodegradable wastes that we generate ?
Answer:
The problems caused by the non-biodegradable wastes are :

  1. If the quantity of non-biodegradable matter increases in the nature then bio-magnification of poisonous chemicals in our body increases.
  2. If the non-biodegradal waste keeps on increasing there will not be left any substance for new organisms.
  3. The increasing quantity of non-biodegradable waste will cause imbalance of ecosystem.

Question 8
If all the waste we generate is biodegradable, will this have no impact on the environment ?
Answer:
If all the waste we generate is biodegradable, it will also have impact on the environment. If it is disposed off properly, the problem of air, water and soil pollution can be lessened to an extent. There would be less health problems and humans would be disease-free.
But if it is not disposed off properly, it will affect the environment adversely.

Question 9
Why is damage to the ozone layer a cause for concern ? What steps are being taken to limit this damage ?
Answer:
The damage to the ozone layer is a cause for concern because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals and also damage the plants.
In an attempt to protect the ozone layer, the United Nations Environment Programme (UNEP) unanimously forged an agreement among its member countries to freeze CFC production at 1986 levels.

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Our environment: Eco-system, Environmental problems, Ozone depletion, waste production and their solutions. Biodegradable and non-biodegradable substances.

Question 1.
Why are some substances biodegradable and some non-biodegradable ?
Answer:
Substances that are broken down by biological processes are said to be biodegradable. In our environment, many of the substances are broken easily by decomposers (bacteria and fungi) as they possess specific enzymes for such activity. However, there are other substances also which are not broken down in this manner and are known as non-biodegradable substances. Since these substances are not degraded by bacteria and fungi, so they persist for a long time. These non-biodegradable substances will be acted upon by physical processes like heat and pressure.

Question 2.
Give any two ways in which biodegradable substances would affect the environment.
Answer:

  1. They may produce foul smell during decomposition process.
  2. They may produce some harmful gases such as ammonia, methane, carbon dioxide, etc., which can further-cause global warming.

Question 3.
Give any two ways in which non-biodegradable substances would affect the environment.
Answer:

  1. These inert substances simply persist in the environment. This means that these substances require land area for dumping.
  2. Excess of fertilizers, pesticides and other chemicals changes soil chemistry and also affects aquatic life.
  3. Most of these chemicals and heavy metal are easily absorbed by the organisms. This causes biological magnification.

Page : 261

Question 1.
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer:
Each step or level of the food chain forms a trophic level. Consider the following food chain:

Question 2.
What is the role of decomposers in the ecosystem?
Answer:
Role of decomposers in the ecosystem :

  1. They help in breaking down the complex organic into simple inorganic that go into the soil and are used up by the plants.
  2. They the nutrient pool of the putting In this way, ad as cleansing agents of nature.
  3. They help in maintaining the fertility of by adding humus content to it.

Page : 264

Question 1.
What is ozone and how does it affect any ecosystem?
Answer:
Ozone (O3) is a molecule formed by three atoms of oxygen. At the higher of the atmosphere, it shields the surface of the earth from ultraviolet (UV) radiation from the Sun. It may affect any ecosystem in the following ways :

  1. At the surface of the earth, it is a deadly poison for all lower forms of life.
  2. If this layer gets depleted, then it may cause cancer in human beings including other plants and animals.

Question 2.
How can you help in reducing the problem of waste disposal? Give any two methods?
Answer:

  1. By changing our lifestyle and change in attitude will reduce disposable waste.
  2. Reducing packaging.
  3. Recycling of waste.
  4. Preparing compost of biodegradable waste.

Excercise:

Question 1.
Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer:
(c) Fruit-peels, cake and lime-juice and (d) Cake, wood and grass

Question 2.
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Grass, goat and human

Question 3.
Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer:
(d) All of the above

Question 4.
What will happen if we kill all the organisms in one trophic level?
Answer:
If we kill all the organisms in one trophic level, then transfer of energy as well as matter to next higher level will stop. It will lead to over- population at one particular level causing amongst the individuals. This would seriously disturb the food chain and can cause the collapse of an ecosystem even.

Question 5.
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?
Answer:
Yes, the impact Of removing all the Organisms in a trophic level will be different for different trophic levels. It will not be possible to remove any organism in any trophic level without causing damage to the ecosystem.

Question 6.
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer:
The accumulation of harmful chemicals in the body of living organisms at different trophic levels in a food chain is called biological magnification. Yes, the concentration of these harmful chemicals will be different at different trophic levels. It will be maximum at the last trophic levels which is mostly of the top carnivores (quaternary consumers).

Question 7.
What are the problems caused by the non-biodegradable wastes that we generate?
Answer:
(i) Non-biodegradable wastes persist in the environment for a long time and cause greater harm to the various members of the ecosystem by causing biological magnification.
(ii) Non-biodegradable waste such as fertilizers, pesticides, weedicides, etc., changes the soil chemistry. in turn affects the fertility of soil and subsequently reduces the crop yield.

Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer:
Biodegradable waste will be recycled easily by the decomposers such as bacteria and fungi. It will have only this bad impact on our environment that, many Of the gases released during decomposition process may result in global warming.

Question 9.
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer:
The ozone shields the surface of the earth from ultraviolet (UV) radiation from the sun. These radiations are highly damaging as they can cause cancer in both plants and animals, damage to eyes and immune system. They can also lead to variations in global rainfall, ecological disturbances and dwindling of global food supplies. Due to these reasons, damage to the ozone layer is a major cause for concern.
Steps which are taken to limit this damage :

  1. To decrease the use of synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
  2. In 1987, the United Nations Environment Programme (UNEP) succeeded in reaching an agreement to freeze CFC production at 1986

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