Science Class- 10
Class 10 - Chapter 13: Our Environment
Q1. Which of the following groups contain only biodegradable items?
Answer: (a) Grass, flowers and leather.
Biodegradable substances are those that can be broken down by microorganisms into simpler substances. Grass, flowers and leather are all biodegradable materials.
Q2. Which of the following constitute a food-chain?
Answer: (b) Grass, goat and human.
A food chain shows the transfer of food and energy from one organism to another.
Grass → Goat → Human
This is a correct food chain because the goat feeds on grass and humans can consume goat products.
Q3. Which of the following are environment-friendly practices?
Answer: (d) All of the above.
The following practices help in protecting the environment:
- Using cloth bags instead of plastic bags.
- Switching off unnecessary lights and fans.
- Walking short distances instead of using vehicles.
Therefore, all the given practices are environment-friendly.
Q4. What will happen if we kill all the organisms in one trophic level?
Each trophic level plays an important role in maintaining ecological balance.
If all organisms of one trophic level are removed:
- The food chain will be disturbed.
- Organisms at the next higher trophic level may starve due to lack of food.
- The population of organisms at the lower trophic level may increase excessively.
- The balance of the ecosystem may be seriously affected.
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?
Yes, the impact will be different for different trophic levels because each level performs a specific function in the ecosystem.
For example:
- Removal of producers will affect the entire food chain because they are the primary source of food and energy.
- Removal of herbivores or carnivores will disturb the population balance of other organisms.
No trophic level can be removed completely without causing damage to the ecosystem.
Q6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Biological magnification is the gradual increase in the concentration of harmful chemicals such as pesticides in the bodies of organisms at successive trophic levels of a food chain.
Yes, the level of magnification increases at higher trophic levels.
This happens because these harmful substances are not broken down easily and accumulate in the bodies of organisms.
Example:
Water → Small Fish → Large Fish → Bird
The concentration of harmful chemicals is highest in the bird.
Q7. What are the problems caused by the non-biodegradable wastes that we generate?
Non-biodegradable wastes remain in the environment for long periods because microorganisms cannot decompose them.
Problems caused are:
- Environmental pollution.
- Soil and water contamination.
- Harm to animals that may swallow plastic materials.
- Accumulation of toxic substances in food chains.
- Reduction in the aesthetic beauty of surroundings.
Q8. If all the waste we generate is biodegradable, will this have no impact on the environment?
No, even biodegradable waste can affect the environment if produced in large quantities.
Excessive biodegradable waste may:
- Produce foul smell during decomposition.
- Become a breeding ground for disease-causing organisms.
- Cause pollution if not managed properly.
- Consume large amounts of oxygen during decomposition.
Therefore, proper waste management is necessary even for biodegradable waste.
Q9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
The ozone layer acts as a protective shield around the Earth by absorbing harmful ultraviolet (UV) radiations from the Sun.
Damage to the ozone layer allows more UV radiations to reach the Earth's surface.
Harmful effects include:
- Skin cancer.
- Cataract and other eye diseases.
- Weakening of the immune system.
- Damage to plants and marine life.
Steps taken to limit ozone depletion:
- Reducing the use of chlorofluorocarbons (CFCs).
- Using ozone-friendly refrigerants and aerosols.
- Implementing international agreements such as the Montreal Protocol.
- Creating awareness about environmental protection.