PAGE NO-212
Q1. What are trophic levels? Give an example of a food chain and identify the different trophic levels in it.
Solution:
Trophic levels are the different stages in a food chain where energy and food transfer occur. Each level represents a position of organisms in the chain.
Example: Grass → Goat → Man
Here,
- Grass is the first trophic level (producer),
- Goat is the second trophic level (primary consumer),
- Man is the third trophic level (secondary consumer).
Q2. What role do decomposers play in the ecosystem?
Solution:
Decomposers break down dead plants and animals, cleaning the environment. They recycle nutrients by returning elements to soil, water, and air, which producers reuse. This process also frees space for new life in the ecosystem.
PAGE NO-214
Q1. Why are some substances biodegradable and others non-biodegradable?
Solution:
Biodegradable substances can be broken down by microorganisms like bacteria and decomposers, typically natural materials like wood or paper. Non-biodegradable substances, such as plastics, resist decomposition because these microbes cannot break them down.
Q2. Give two ways biodegradable substances affect the environment.
Solution:
- They keep the environment clean by decomposing easily.
- They smoothly travel through geochemical cycles, aided by decomposers.
Q3. How do non-biodegradable substances affect the environment?
Solution:
- They cause pollution in air, water, and soil.
- They can lead to biomagnification, accumulating harmful substances up the food chain, impacting humans.
PAGE NO -216
Q1. What is ozone, and how does it affect the ecosystem?
Solution:
Ozone is a molecule of three oxygen atoms, acting as a protective layer in the atmosphere that blocks harmful UV rays from the sun. Without it, living organisms would face health risks such as skin cancer.
Q2. How can you help reduce waste disposal problems? Give two methods.
Solution:
- Follow the 3 Rs: Reduce, Reuse, Recycle. For example, use public transport to reduce pollution and recycle plastics.
- Prepare compost using biodegradable kitchen waste.
EXERCISE
Q1. Which groups contain only biodegradable items?
Solution:
- Grass, flowers, and leather
- Fruit peels, cake, and lime juice
- Cake, wood, and grass
(Note: Groups containing plastic are not biodegradable.)
Q2. Which of the following constitutes a food chain?
Solution:
Grass → Goat → Human
Grass is the producer, goat the primary consumer, and human the secondary consumer.
Q3. Which practices are environment-friendly?
Solution:
All of the following:
- Carrying cloth bags for shopping,
- Switching off unused lights and fans,
- Walking instead of using vehicles.
Q4. What happens if all organisms at one trophic level are killed?
Solution:
The food supply for the next level stops, causing a disturbance: higher levels lose food and die off, and lower levels may grow unchecked, unbalancing the ecosystem.
Q5. Is the impact of removing organisms the same for all trophic levels? Can any be removed without damage?
Solution:
No, impacts vary. Removing any level disrupts the food chain, affecting survival at all levels. No trophic level can be removed without harming the ecosystem.
Q6. What is biological magnification? Does it vary in the ecosystem levels?
Solution:
Biological magnification is the increase of toxic non-biodegradable substances through food chain levels. The concentration rises at higher trophic levels, affecting top consumers more severely.
Q7. What problems do non-biodegradable wastes cause?
Solution:
They do not break down, causing dumping issues, soil infertility, and contamination of groundwater. Toxic substances can enter food chains at upper levels.
Q8. Will only biodegradable waste avoid environmental impact?
Solution:
No. Excess biodegradable waste decomposes slowly, emitting foul odors, breeding harmful organisms, and causing oxygen depletion in water bodies.
Q9. Why is ozone layer damage a concern? What steps limit this damage?
Solution:
The ozone layer protects life from harmful UV rays which cause health problems and harm plants. Ozone depletion, mainly due to CFC pollutants, disrupts this protection. To limit damage, countries follow UNEP guidelines to reduce CFC use.
This rewritten content retains the original explanations and word counts while presenting the information in a natural and clear human style.