Q. 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
  • Ans. (d) All of the above
 Explanation :

Being eco-friendly refers to a way of life that is better for the environment. It involves taking little measures towards ensuring that the Earth’s environment is properly maintained for current and future generations. Carrying cloth bags to put purchases in while shopping, switching off unnecessary lights and fans, walking to school instead of getting your mother to drop you on her scooter are all examples of environment friendly practices.

Q. Excessive exposure of humans to UV rays results in :

(i) damage to immune system

(ii) damage to lungs

(iii) skin cancer

(iv) peptic ulcers

(a) (i), (ii)

(b) (ii), (iv)

(c) (i), (iii)

(d) (iii), (iv)

Ans. (c) (i), (iii)

 Explanation :

UV rays are extremely hazardous to humans, animals, and even plants. It can cause skin cancer, cataracts in the eyes, and immune system damage by reducing the body’s response to infections.

Q. Why is damage to the ozone layer a cause of concern? What steps are being taken to limit this damage?

Ans. Ozone layer is found in stratosphere which prevents the harmful UV rays of sun from entering earth’s surface. Various ozone depleting substances like CFCs cause a great damage to ozone layer thus leading to its depletion. So harmful UV rays from sun can easily pass through this layer and cause various genetic disorders, mutations, cancer, eye diseases etc., in humans. UV rays also affect plants and animals.
In 1987, UNEP [United Nations Environment Programme] succeeded in forging an agreement called Montreal Protocol which states the significance and measures to reduce the use of CFCs and replace CFCs with other alternatives.

Q. Why are some substances biodegradable and some non-biodegradable?

Ans. There are various types of waste substances released into our environment. Those substances which are degraded into simpler form naturally by the action of microbes like bacteria or fungi are called biodegradable substances. Examples–Vegetables and fruits peels, paper, agricultural wastes etc.
Those substances which cannot be degraded into simpler forms naturally by the action of microbes are called non-biodegradable substances. Examples–Aluminium foils, plastic bottles, glass apparatus etc.

Q. What is the role of decomposers in the ecosystem?

Decomposers act upon dead and decay organisms and convert them into simpler forms. These simple substances get mixed up in the soil and are used as nutrients by the producers. From producers it goes to consumers and so on. They maintain the balance in the ecosystem and provide space for new life in ecosystem.

Q. What will happen if we kill all the organisms in one trophic level?

Ans. If we kill all the organisms of one trophic level, it will lead to an increase in the number of organisms at the lower trophic level and decrease in the number of organisms at the higher trophic level. This will result in disruption in the food web and hence the ecosystem.

Q. How can you help in reducing the problem of waste disposal? Give any two methods.

Ans. We can help in reducing the problem of waste disposal by the following two methods:

  • 1. By separating biodegradable substances from non-biodegradable substances.
  • 2. By putting the biodegradable organic waste into compost pits dug in the ground and preparing compost.

Q. 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?

Ans. Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, If all producers will be removed then all herbivores will die of starvation. The various categories of carnivores which depend on herbivores for food will also be affected. Similarly if we will remove all organisms of higher trophic level the number of organisms in lower trophic level will increase thus creating imbalance in the ecosystem. So if organisms of any trophic level would be removed it will cause damage to the ecosystem.

Q. What are trophic levels? Give an example of food chain and state the different trophic levels in it?

Ans. The distinct sequential steps or levels in the food chain where transfer of energy occurs are referred to as trophic levels.

  • Example of a food chain is:
  • Grass → Grasshopper → Lizard → Snake → Hawk Grass is producer, it belongs to first trophic level.
  • Grasshopper is primary consumer, it belongs to second trophic level. Lizard is secondary consumer, it belongs to third trophic level. Snake is tertiary consumer and it belongs to fourth trophic level and hawk is quaternary consumer, it belongs to fifth trophic level.

Q. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

  • Ans. The increase in concentration of harmful toxic substances in the body of organisms at each trophic level of a food chain is called biological magnification. Yes, the levels of this magnification will be different at different levels of the ecosystem because the concentration of chemicals goes on increasing at different trophic levels. It is maximum at higher trophic levels and minimum at lower trophic levels. Suppose a food chain is Grass → Rabbit → Eagle, it will be the highest in eagle and minimum in grass.

Q. What is ozone and how does it affect any ecosystem?

  • Ans. Ozone is a triatomic molecule made of three oxygen atoms. It is present as a layer in stratosphere which prevents the harmful UV radiations of sun from entering the earth’s surface, thus protecting us from skin cancers, genetic mutations, eye diseases like cataract etc. Ozone is a molecule made from three atoms of oxygen. Th e harmful chemicals like CFCs which are used as coolants in refrigerators, air conditioners when released into atmosphere break down the ozone thus leading to depletion of ozone layer. Hence harmful UV rays can easily pass through ozone layer and cause various types of disorders in humans, plants and animals.

Q. Suggest any four activities in daily life which are ecofriendly?

  • Ans.The four activities in daily life which are ecofriendly are:
  • 1. Carrying paper bags instead of polythene bags for shopping.
  • 2. Use of compost and biofertilizers, biopesticides instead of chemical fertilizers and pesticides.
  • 3. Segregating biodegradable and non-biodegradable substances and putting them in separate dustbins.
  • 4. Rain water harvesting.

Q. Give any two ways in which biodegradable substances would affect the environment.

  • Ans. The two ways in which biodegradable substances would affect the environment are:
  • 1. Decomposition of biodegradable substances results in production of foul smell.
  • 2. The area where biodegradable wastes are accumulated serves as a good breeding place for mosquitoes, flies etc. which are the main carriers of germs for diseases like cholera, jaundice, typhoid etc.

Q. What are the problems caused by the non-biodegradable wastes that we generate?

  • Ans. The problems caused by the non-biodegradable wastes are:
  • 1. As non-biodegrdable substances cannot be degraded naturally so they accumulate in the soil causing pollution and also reduces the fertility of the soil.
  • 2. Some pesticides like DDT, mercury etc., which are non-biodegradable undergo biological magnification by entering into food chain.
  • 3. If these substances do not undergo proper disposal techniques they will accumulate in soil thus will reduces a the fertility of soil.
  • 4. Some harmful non-biodegradable substances may cause diseases in living organisms.

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

  • Ans. If all the waste we generate is biodegradable then their decomposition at right time will not be possible as number of decomposers would be less as compared to the amount of biodegradable substances. It will get accumulated in the environment causing foul smell and will form a good breeding place for flies, mosquitoes etc., which will carry many disease causing germs. Thus various diseases like cholera, typhoid, jaundice, malaria, dengue etc., will be spread.