10th Standard, Science CHAPTER 13
Our Environment
E X E R C I S E S
- 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: a, c, d - 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
- 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
- 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 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. The transfer of food energy to the next trophic level will stop. The organisms in the higher trophic level will die.The organisms in the lower trophic level will increase in population. This will break the food chain.
- 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: If all plants are removed, then herbivores will die because they won’t have food.
If herbivores are removed, then carnivores will starve and die.
If all primary consumers are removed, then secondary consumers will starve and die.
If all organisms in a trophic level are removed, then the population of organisms at the lower trophic level will increase, and the population of organisms at the higher trophic level will decrease. Energy flows unidirectionally in food chains, with energy loss at each trophic level.
No. The organisms of any trophic level can’t be removed without causing any damage to the ecosystem.
- What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer: Biological magnification is the process by which harmful chemicals increase in concentration as they move up the food chain. The substances become more concentrated as they move up the food chain, and are incorporated into the diet of organisms at higher levels. For example, pesticides or heavy metals can enter lakes, rivers, and oceans, and then move up the food chain into aquatic organisms, fish, birds, animals, and humans.
Yes, biological magnification levels vary at different levels of an ecosystem. It increases as you move up the food chain, and is highest at the top levels. - What are the problems caused by the non-biodegradable wastes that we generate?
Answer: Non-biodegradable waste can cause many problems, including pollution, soil damage, and harm to living organisms.
Burning non-biodegradable waste releases toxic gases.
Non-biodegradable waste can accumulate in the soil and make it barren.
Non-biodegradable waste can pollute water.
Non-biodegradable waste can deplete soil fertility. Non-biodegradable waste can make soil unsuitable for plant growth.
Chemicals like DDT can accumulate in the food chain. Cattle can die after eating plastics. Non-biodegradable waste can harm living organisms.
- If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer: Biodegradable waste can still impact the environment, even if it’s handled properly. This is because of the amount of waste generated, the time it takes to decompose, and the impact of decomposition on the environment. Too much biodegradable waste can create a breeding ground for flies, mosquitoes, and worms that spread disease. - Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer: At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings. Damage to the ozone layer is a major concern because it allows harmful ultraviolet (UV) radiation from the sun to reach Earth’s surface.
To limit this damage, the primary step taken globally is to significantly reduce the use of chlorofluorocarbons (CFCs) through the Montreal Protocol, an international treaty that restricts the production and consumption of ozone-depleting substances. In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels. It is now mandatory for all the manufacturing companies to make CFC-free refrigerators throughout the world.
Some more Text Book Questions:
- What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer: The steps in a food chain where energy and food are transferred are called trophic levels.
Example of food chain:
Grass Insects Frogs Snakes - Grass -The first trophic level, where food is produced
- Insects – The second trophic level, where primary consumers eat plants
- Frogs – The third trophic level, where secondary consumers eat primary consumers
- Snakes – The fourth trophic level, where tertiary consumers eat secondary consumers
- What is the role of decomposers in the ecosystem?
Answer: Decomposers play a vital role in the ecosystem by breaking down dead organisms and returning nutrients to the soil, water, and air. This process helps plants grow and reproduce, and keeps the environment clean. - Why are some substances biodegradable and some non-biodegradable?
Answer: Substances that are broken down by biological processes are said to be biodegradable. Substances that are not broken down in this manner are said to be non-biodegradable. These substances may be inert and simply persist in the environment for a long time or may harm the various members of the eco-system.
Substances are considered biodegradable if they can be broken down by microorganisms like bacteria and fungi into simpler organic compounds, while non-biodegradable substances lack the chemical structure that allows them to be decomposed by these organisms, usually because they are synthetic materials with complex bonds that microbes cannot readily break down; essentially, the key difference lies in the ability of microorganisms to digest and utilize the substance’s components. - Give any two ways in which biodegradable substances would affect the environment.
Answer: When biodegradable substances decompose, they release carbon into the atmosphere. Biodegradable waste can pollute water. Biodegradable waste can pollute the land.
- Give any two ways in which non-biodegradable substances would affect the environment.
Answer: The two ways in which non-biodegradable substances would affect the environment are,
i) They contaminate soil and water resources as they cannot be decomposed by micro-organisms.
(ii) These substances, when accidentally eaten by stray animals, can harm them and can even cause their death. - What is ozone and how does it affect any ecosystem?
Answer: Ozone is a gas made of three atoms of oxygen. It is a hazardous gas that is prevalent high up in the atmosphere. Ozone is a vital gas for all sorts of ecosystems on earth as it protects the environment from the damaging effects of UV radiation causing skin cancer and cataract and impairs our immune system. Depletion of this ozone layer can significantly impact ecosystems by exposing organisms to harmful UV rays, potentially causing damage to plant life, disrupting marine ecosystems, and increasing the risk of skin cancer in humans.
- How can you help in reducing the problem of waste disposal? Give any two methods.
Answer: The two ways we can help in reducing the problem of waste disposal are,
a. Minimize using single-use disposable items by opting for reusable alternatives like water bottles and shopping bags.
b. Properly separate waste at home by sorting recyclable materials from general trash to ensure they can be recycled effectively.
