Chapter 15 – Our Environment Solutions
Question - 1 : - What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer - 1 : -
In the food chain, the transfer of food or energy takes place at various levels and these levels are known as trophic levels.
Example:
Grass → Goat → Man
In the food chain,
• Grass represents the first trophic level
• The goat represents the second trophic level
• Man represents the third trophic level
Question - 2 : - What is the role of decomposers in the ecosystem?
Answer - 2 : -
Following is the role of a decomposer in the ecosystem:
• They act as a cleansing agent of the environment by decomposing the dead plants and animals
• They help in recycling the nutrients
• They provide space for new beings in the biosphere by decomposing the dead
• They help in putting back the various elements into water, soil and air for the reuse of producers like crop plants.
Question - 3 : - Why are some substances biodegradable and some non-biodegradable?
Answer - 3 : - The reason why some substances are biodegradable and some non-biodegradable is because the microorganisms like bacteria and decomposers like saprophytes have a specific role to play. They can breakdown only natural products like paper, wood, etc. but they cannot breakdown man-made products like plastics. Based on this, some substances are biodegradable and some non-biodegradable.
Question - 4 : - Give any two ways in which biodegradable substance would affect the environment.
Answer - 4 : -
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.
Question - 5 : - Give any two ways in which non-biodegradable substances would affect the environment.
Answer - 5 : -
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 human.
Question - 6 : - What is ozone and how does it affect the ecosystem?
Answer - 6 : - Ozone is a molecule formed by the three atoms of oxygen and is known as an isotope of oxygen. The main function of 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.
Question - 7 : - How can you help in reducing the problem of waste disposal? Give any two methods.
Answer - 7 : -
Following are the ways to reduce the problem of waste disposal:
• 3 R’s: By following the 3 R’s one can reduce the problem of waste disposal. The 3 R’s are reduce, recycle and reuse. Reducing the usage of their own vehicles and opting for public transport can reduce air pollution. Recycling and reusing of plastics is also a way to reduce waste disposal.
• Preparation of compost: All the biodegradable waste like kitchen waste, can be dumped in the compost.
Question - 8 : - Which of the following groups contain only biodegradable items?
Answer - 8 : -
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
c) Fruit peels, cake and lime juice
d) Cake, wood and grass
Above all are the groups that contain only biodegradable items. Since plastic is not a biodegradable substance, that group cannot be considered as a biodegradable.
Question - 9 : - Which of the following constitute a food-chain?
Answer - 9 : -
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
Here, the goat is the producer, goat is the primary consumer and human is the secondary consumer.
Question - 10 : - Which of the following are environment-friendly particles?
Answer - 10 : -
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