NCERT Exemplar problems for Class 10 Science Chapter 15 Our Environment

Short Answer Questions

Question 1. Why is improper disposal of waste a curse to environment?
Answer. Improper disposal of waste is a curse to environment because it pollutes the environment, air, water, soil and cause harmful effects on living organisms.
For example, passage of sewage into water body cause eutrophication, killing of animals and source of water-borne pathogens.

Question 2. Write the common food chain of a pond ecosystem.
Answer. Phytoplanktons and aquatic plants ———–> Zooplanktons and small aquatic animals and larvae, insects, etc. ———–> Fish ———–>Bird.

Question 3. What are the advantages of cloth bags over plastic bags during shopping?
Answer. Advantages of cloth bags:

1. They are made of biodegradable material.
2. They can be recycled and reused.
3. They do not pollute the environment.
4. They are strong and more durable than plastic bags.
5. They are capable of carrying more things.
6. They are washable.

Question 4. Why are crop fields known as artificial ecosystems?
Answer. Crop fields are known as artificial ecosystems because they are man-made and some biotic and abiotic components are maintained, nourished and reaped by human beings.

Question 5. We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?
Answer. An aquarium is an artificial and incomplete ecosystem compared to pond or lakes which are natural, self-sustaining and complete ecosystem where there is a perfect recycling of materials. Therefore, it needs to be cleaned.

Long Answer Questions

Question 6. Suggest any four activities in daily life which are eco-friendly.
Answer.

1. Use of cloth bags instead of plastic bags.
2. Gardening.
3. Harvesting of rainwater and preventing wastage of resources.
4. Use of compost.

Question 7. Indicate the flow of energy in an ecosystem. Why is it unidirectional ? Justify.
Answer. The flow of energy generally is as follows:
Sun ———>Producers ———> Herbivores ———> Carnivores
Since, flow is progressively from one trophic level to another and does not revert back, it is said to be unidirectional, i.e. from sun to plants, plants to animals,
animals to other animals and organic remains to decomposers. Thus, the available energy decreases in the higher trophic levels making impossible for energy flow in reverse direction.

Question 8. Name the wastes which are generated in your house daily. What measures would you take for their disposal?
Answer. The wastes generated daily are kitchen wastes, paper wastes like newspapers, bags, envelopes, plastic bags, vegetable and fruit peels, dust and empty cartons, etc. Measures for disposal are:

1. Separation of biodegradable and non-biodegradable recyclable and non-recyclable wastes.
2. Safe disposal of plastic bags.
3. Preparation of compost from kitchen wastes for home garden or given to waste collector for disposal.
4. Paper waste can be given for recycling.

Question 9. Explain some harmful effects of agricultural practices on the environ-ment.
Answer. Some harmful effects of agricultural practices on the environment are as follows:

1. Use of fertilisers change the chemistry of soil and kills useful microbes.
2. Use of non-biodegradable pesticides leads to bio-magnification.
3. Extensive cropping causes loss of soil fertility.
4. Use of ground water for agriculture ‘ has resulted in lowering water table,
5. Natural ecosystems and habitat have been damaged during clearing of land for agriculture.