NCERT Solutions Class 10 Science
The NCERT Solutions in English Language for Class 10 Science Chapter – 15 (Our Environment) has been provided here to help the students in solving the questions from this exercise.
Chapter – 15 (Our Environment)
Questions
1. What are trophic levels ? Give an example of a food chain and state the 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
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.
2. What is the role of decomposers in the ecosystem ?
Answer – Decomposers include micro-organisms such as bacteria and fungi that obtain nutrients by breaking down the remains of dead plants and animals. They help in the breakdown of organic matter or biomass from the body of dead plants and animals into simple inorganic raw materials, such as CO2, H2O, and some nutrients.
Questions
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.
2. Give any two ways in which biodegradable substances would affect the environment.
Answer – The following are the ways in which biodegradable substances would affect the environment:
- They keep the environment clean as they are easily decomposed.
- They can easily go through the geochemical cycle with the help of decomposers.
3. Give any two ways in which non-biodegradable substances would affect the environment.
Answer – The following are the ways in which non-biodegradable substances would affect the environment:
- They cause air, soil and water pollution.
- They may cause bio-magnification in the food chain resulting in the end of humans.
Questions
1. What is ozone, and how does it affect the ecosystem?
Answer – Ozone is a molecule formed by the three atoms of oxygen and is known as an isotope of oxygen. The main function of the ozone layer is to provide protection to the earth’s surface from the harmful UV rays of the sun. These rays are harmful to living organisms and may result in skin cancer.
2. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer – The following measures can be adopted for reducing the problem of waste disposal:
- Recycling The solid wastes like paper, plastics and metals, etc. are recycled.
- 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.
Exercises
1. Which of the following groups contains only easily biodegradable items ?
(a) Grass, flower 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.
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
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 the above.
Answer – (d) All the above.
4. What will happen if you kill all the orgainsms in one trophic level ?
Answer – If we kill all the organisms in one trophic level, the food supply to the next level will stop, resulting in an imbalance of the ecosystem. As a result, animals in the higher levels will die, making the growth of animals in the lower trophic level increase in an enormous way. All of this will affect the overall balance in the ecosystem.
5. Will the impact of removing all the organisms in the 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.
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.
7. What are the problems caused by the nonbiodegradable waste we generate ?
Answer – The following are the problems caused by non-biodegradable wastes:
- These substances cannot be decomposed by microorganisms.
- As the quantity increases, dumping becomes a problem.
- Non-biodegradable wastes, like heavy metals, may enter the food chain at the upper trophic levels.
- They may escape to the groundwater, which causes soil infertility and disturbance in the pH of the soil.
8. If all the waste we generate is biodegradable, will this have no impact on the environment ?
Answer – Generation of only biodegradable waste will have a positive impact on the environment. There will not be any pollution caused by the non-biodegradable wastes. The problem associated with waste management and disposal will also not occur. The population of decomposers will increase to breakdown the extra biodegradable waste generated.
9. Why is damage to the ozone layer a cause of 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.
