Question Bank — How Nature Works in Harmony

Section A — MCQs (10 questions, 1 mark each)

1. Which of the following correctly defines a population?
   (a) All living organisms in a pond
   (b) A group of organisms of the same kind living together in a habitat at a given time
   (c) Different populations sharing the same habitat
   (d) All biotic and abiotic components of a forest

2. In the study of two ponds, Pond A (with fish) had more flowering plants around it than Pond B (without fish). This is because:
   (a) Fish increase the amount of sunlight reaching the plants
   (b) Fish eat dragonfly larvae, reducing dragonflies that eat pollinators
   (c) Fish directly pollinate the flowers
   (d) Absence of fish increases oxygen for plants

3. Which statement about producers and consumers is correct?
   (a) Producers are heterotrophs that depend on other organisms for food
   (b) Consumers include herbivores, carnivores and omnivores
   (c) Decomposers are also called autotrophs
   (d) Only carnivores occupy the first trophic level

4. Assertion (A): Decomposers are essential for recycling nutrients in an ecosystem.
   Reason (R): Bacteria and fungi break down dead matter into simpler substances that return to the soil.
   (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 but R is false
   (d) A is false but R is true

5. The overlap of a river (aquatic) with forests and farmland (terrestrial) shows that:
   (a) Ecosystems are always isolated from each other
   (b) Different ecosystems can interact at a given place
   (c) Only human-made ecosystems exist in nature
   (d) Abiotic components do not influence biotic components

6. Assertion (A): Competition among organisms helps maintain balance in an ecosystem.
   Reason (R): Without competition, one species may multiply excessively and disturb the ecosystem.
   (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 but R is false
   (d) A is false but R is true

7. In a food chain, grass → grasshopper → frog → snake, the trophic level occupied by the frog is:
   (a) First trophic level
   (b) Second trophic level (herbivore)
   (c) Third trophic level (small carnivore)
   (d) Fourth trophic level (large carnivore)

8. Which interaction is shown when an orchid grows on a tree branch?
   (a) Mutualism
   (b) Commensalism
   (c) Parasitism
   (d) Competition

9. Human activities such as cutting mangroves in the Sundarbans mainly lead to:
   (a) Increase in biodiversity
   (b) Disruption of natural balance and loss of habitat protection during storms
   (c) Decrease in pollution levels
   (d) Automatic formation of new protected areas

10. Which of the following is an example of a human-made ecosystem?
    (a) A natural pond
    (b) A fish pond or agricultural farm that requires human management
    (c) A dense forest with overlapping ecosystems
    (d) A river flowing through grasslands

Section B — Very Short Answer (6 questions, 2 marks each)

1. Differentiate between biotic and abiotic components of a habitat with one example of each from a pond.

2. What is a community? How is it different from a population?

3. State two ways in which plants (biotic components) influence abiotic components in an ecosystem.

4. Define decomposers. Why are they also called saprotrophs?

5. List any two differences between a food chain and a food web.

6. What is the role of protected areas such as national parks in maintaining ecosystem balance?

Section C — Short Answer (5 questions, 3 marks each)

1. Describe the observations from the pond study (Pond A with fish and Pond B without fish). Explain how the presence of fish indirectly affects seed production in nearby plants.

2. Draw a simple labelled diagram of a grassland food chain involving at least four organisms. Mark the trophic levels.

3. Explain any three types of interactions among biotic components (mutualism, commensalism and parasitism) with one example of each from the chapter.

4. How do changes in rainfall and temperature, along with cutting of trees, lead to elephants entering human habitats? Link this to loss of habitat and corridors.

5. What is monoculture? State two harmful effects of practising monoculture and excessive use of synthetic pesticides on soil and biodiversity.

Section D — Long Answer (3 questions, 5 marks each)

1. Define an ecosystem. Describe the different types of interactions (between biotic–abiotic, abiotic–abiotic, and biotic–biotic components) that occur in a habitat. Support your answer with at least three examples from a pond or forest ecosystem. (Include a labelled diagram showing one example of each type of interaction.)

2. What is a trophic level? With the help of a labelled pyramid diagram, explain the positions of producers, herbivores, small carnivores and large carnivores in a food chain. Why is the number of organisms usually highest at the base of the pyramid?

3. “One small change in an ecosystem can lead to many other changes.” Explain this statement using the example of pollution in a pond or the decline of frog populations due to export. Describe the cascading effects on other organisms and the environment.

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1: In several states, elephants enter farms when forests shrink due to tree cutting and changes in rainfall. Wildlife corridors have been marked to allow safe movement of elephants between forest patches.

(a) What are biotic and abiotic factors responsible for elephants moving into human areas?
(b) How do corridors help reduce conflict between wildlife and humans?
(c) Name two states mentioned where this problem is common.
(d) How does this situation show interconnection between nature’s elements?

Case 2: Researchers observed that ponds with fish had fewer dragonflies but more bees and butterflies, leading to better pollination and seed production in nearby plants compared to ponds without fish.

(a) What is the direct effect of fish on dragonfly larvae?
(b) How does reduction in dragonflies benefit pollinators?
(c) Name the type of interaction between fish and dragonflies.
(d) If humans overfish in such ponds, predict one possible effect on the surrounding plants.

Section F — HOTS and Application (4 questions, 3 marks each)

1. Predict-and-justify: What would happen to the populations of grasshoppers, frogs and snakes if all the grass in a grassland ecosystem suddenly died due to drought? Justify your answer.

2. Analyse an unexpected observation: In a school garden, students observed that after introducing fish in a small pond, the number of mosquitoes decreased but the number of flowering plants around the pond increased. Analyse the possible chain of events that led to this observation.

3. Apply to an unfamiliar real-life situation: A village near a river notices that after large-scale removal of trees on the riverbank, the river water becomes muddy during rains and fish catches decline. Apply your understanding of biotic–abiotic interactions to explain these changes.

4. Compare two situations: Compare the effect on soil health and pest population when a farmer practises (i) monoculture with heavy pesticide use versus (ii) mixed cropping with natural predators present. Justify which situation is more likely to maintain ecological balance.