How Nature Works in Harmony — Hard

Q1. Consider the following components of a pond habitat: I. Fish II. Soil at the bottom III. Microorganisms in water Which of these are biotic components?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three

Q2. Refer to Fig. 12.19 showing nested circles of population, community and ecosystem. Which of the following statements is WRONG?

• A. A community is larger than a population
• B. A community is smaller than an ecosystem
• C. An ecosystem is part of a community
• D. A population is part of a community

Q3. Look at the food chain: Grass → Grasshopper → Frog → Snake. If frogs disappear from this ecosystem, which is the MOST likely outcome?

• A. Grasshopper population increases and snake population decreases
• B. Both grasshopper and snake populations increase
• C. Grasshopper population decreases and snake population increases
• D. Neither population changes because grass is unaffected

Q4. Assertion (A): In the 1980s, large-scale export of Indian bullfrog legs led to an increase in pesticide use by Indian farmers. Reason (R): Frogs eat insects; with fewer frogs, agricultural pests rose, forcing farmers to use more synthetic pesticides.

• A. Both A and R are true, and R is the correct explanation of A.
• B. Both A and R are true, but R is NOT the correct explanation of A.
• C. A is true, R is false.
• D. A is false, R is true.

Q5. Fig. 12.13 shows: plants die → less oxygen → fish die → more insects → plants damaged by pests. The figure best illustrates that

• A. One small change in an ecosystem can trigger many other changes
• B. Pollution affects only fish in a pond and nothing else
• C. Insects can survive in any pond regardless of oxygen
• D. Plants and fish populations are independent of each other

Q6. Researchers compared Pond A (with fish) and Pond B (without fish). Pond A had MORE flowering plants nearby than Pond B. The reason given in the chapter is

• A. Fish directly fertilise the soil around the pond
• B. Fish eat dragonfly larvae, so fewer dragonflies eat fewer bees and butterflies, so more pollinators visit nearby flowers
• C. Fish chase away herbivores from the plants
• D. Fish add oxygen to the soil through their gills

Q7. If all decomposers suddenly disappeared from a forest ecosystem, which of the following would MOST likely happen?

• A. Plants would grow faster because of less competition
• B. Dead matter would pile up and nutrients would not return to the soil
• C. Producers would automatically take over decomposition
• D. The ecosystem would remain unchanged

Q8. Why is it NOT possible to have a sustainable ecosystem with only producers and no consumers or decomposers?

• A. Producers cannot make their own food without consumers
• B. Producers would compete with each other and die
• C. Dead plant matter would accumulate, nutrients would not be recycled, and energy would not flow up trophic levels
• D. Producers do not need sunlight in this case

Q9. Consider three interactions: I. Honeybee and flower II. Orchid and tree branch III. Tick and dog Which correctly matches each with its type?

• A. I — parasitism, II — mutualism, III — commensalism
• B. I — mutualism, II — commensalism, III — parasitism
• C. I — commensalism, II — parasitism, III — mutualism
• D. I — competition, II — predation, III — mutualism

Q10. Selvam from Cuddalore district, Tamil Nadu, said his village was less affected by the 2004 Tsunami compared to nearby villages. The MOST plausible reason given in the chapter is

• A. Strong concrete walls built by villagers
• B. Presence of mangrove forests near the village
• C. The village being far inland
• D. Use of synthetic fertilisers in nearby fields

Q11. Consider the following statements about excessive use of synthetic fertilisers: I. They can reduce soil fertility by decreasing friendly microorganisms. II. They can lower organic matter (humus) in soil. III. Without enough humus, soil becomes more prone to erosion. Which of these are correct?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three

Q12. In Fig. 12.10a (millet, mouse, eagle in a crop field), if numbers are arranged with the highest at the base and the lowest at the top to form a pyramid, the correct order from base to top is

• A. Eagle → Mouse → Millet
• B. Mouse → Millet → Eagle
• C. Millet → Mouse → Eagle
• D. Millet → Eagle → Mouse

Q13. In a grassland ecosystem, classify the following correctly: I. Grass — producer II. Deer — herbivore (consumer) III. Vulture — decomposer Which of the above are correct?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three

Q14. Assertion (A): Abiotic components in an ecosystem are also influenced by biotic components. Reason (R): Plants release oxygen during photosynthesis, roots hold soil and prevent erosion, and plants retain soil moisture.

• A. Both A and R are true, and R is the correct explanation of A.
• B. Both A and R are true, but R is NOT the correct explanation of A.
• C. A is true, R is false.
• D. A is false, R is true.

Q15. Some pests develop resistance to pesticides over repeated use. As a result

• A. Pests become easier to kill with the same pesticide
• B. Farmers can stop using pesticides immediately
• C. The same pesticide becomes less effective and pests are difficult to control
• D. Pests stop eating crops permanently