NCERT Solutions for Class 10 Science Chapter 15 Our Environment

Q1 ) 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 (d) Cake, wood and grass

Q2 ) 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

Q3 ) 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

Q4 ) What will happen if we kill all the organisms in one trophic level?

Answer :

If we kill all the organisms of one trophic level it will create an imbalance in the ecosystem. As an Example, In a food chain Grass ,\(\rightarrow \) Dear \(\rightarrow \) Lion, If we remove all lions then population of deer will increase which will cause over-grazing. This will lead to deforestation. It may even lead to soil erosion causing further conversion of fertile land into barren desert.

Q5 ) 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 :

Impact of removing all organisms of a trophic level is different for different trophic levels.

For example, if we remove producers from a food chain, no organism will get food, if we remove herbivores from a food chain then carnivores will die and producers will also die due to competition for space and nutrients. If all the organisms of a trophic level are removed it will create an imbalance in the ecosystem. Removing any trophic level from a food chain will cause imbalance in an ecosystem.

Q6 ) What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer :

Biological magnification is defined as the phenomena of accumulation or increase in the concentration of some toxic substances at each trophic level. The levels of biomagnification will be different at different trophic levels. For example, in a pond of water, DDT was sprayed and the producers were found to have 0.04 ppm concentration of DDT. Since many types of planktons are eaten by some fishes and clams, their body accumulates 0.23 ppm of DDT. Sea gull that feeds on clams accumulates more DDT as one sea gull eats many clams. Hawk, the top carnivore, has the highest concentration of DDT.

Q7 ) What are the problems caused by the non-biodegradable wastes that we generate?

Answer :

Following are some problems caused by non-biodegradable wastes:
(a) They cause biomagnification.
(b) They increase pollution.
(c) They make environment unclean.
(d) They kill useful microorganisms.

Q8 ) If all the waste we generate is biodegradable, will this have no impact on the environment?

Answer :

If all the waste generated would be biodegradable this will also create problem. As the numbers of decomposers will be quite low so wastes cannot be broken down into harmless simpler substance at right time. It will became breeding ground for flies causing spread of diseases. It will also emits foul smell which makes the life of people miserable.

Q9 ) 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 a cause for concern because:

\(\Rightarrow \) It causes skin darkening, skin cancer, ageing, and corneal cataracts in human beings.

\(\Rightarrow \) It can result in the death of many phytoplanktons that leads to increased global warming.

To limit the damage to the ozone layer, the release of CFCs into the atmosphere must be reduced. CFCs used as refrigerants and in fire extinguishers should be replaced with environmentally-safe alternatives. Also, the release of CFCs through industrial activities should be controlled.