Ecosystem Structure, Food Chains and Energy Flow

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.In an ecosystem, green plants are called:

   • A.consumers
   • B.decomposers
   • C.producers✓ Correct Answer
   • D.scavengers

   Explanation: They make food by photosynthesis.

2. Q2.Herbivores are known as:

   • A.secondary consumers
   • B.producers
   • C.decomposers
   • D.primary consumers✓ Correct Answer

   Explanation: They feed directly on producers.

3. Q3.Which organisms break down dead matter and return nutrients to the soil?

   • A.Producers
   • B.Herbivores
   • C.Decomposers✓ Correct Answer
   • D.Carnivores

   Explanation: Bacteria and fungi are the main decomposers.

4. Q4.A food chain always begins with:

   • A.a herbivore
   • B.a producer✓ Correct Answer
   • C.a carnivore
   • D.a decomposer

   Explanation: Producers capture solar energy.

5. Q5.The ultimate source of energy for almost all ecosystems is:

   • A.the Sun✓ Correct Answer
   • B.Soil
   • C.Water
   • D.Wind

   Explanation: Plants convert sunlight into chemical energy.

6. Q6.Which of these is a terrestrial ecosystem?

   • A.Pond
   • B.River
   • C.Ocean
   • D.Forest✓ Correct Answer

   Explanation: A forest is a terrestrial ecosystem, whereas ponds, rivers and oceans are aquatic.

7. Q7.According to the 10 per cent law, how much energy passes from one trophic level to the next?

   • A.About 50 per cent
   • B.About 10 per cent✓ Correct Answer
   • C.About 90 per cent
   • D.About 100 per cent

   Explanation: The rest is lost mainly as heat.

8. Q8.The term "ecosystem" was coined by:

   • A.Ernst Haeckel
   • B.Eugene Odum
   • C.A. G. Tansley✓ Correct Answer
   • D.Charles Elton

   Explanation: He used it in 1935.

9. Q9.Which ecological pyramid is always upright?

   • A.Pyramid of numbers
   • B.Pyramid of biomass
   • C.Pyramid of age
   • D.Pyramid of energy✓ Correct Answer

   Explanation: Energy decreases at each higher trophic level.

10. Q10.Interlinked food chains in an ecosystem form a:

    • A.food web✓ Correct Answer
    • B.food pyramid
    • C.trophic cycle
    • D.nutrient web

    Explanation: A web is more stable than a single chain.

11. Q11.Which bacteria fix atmospheric nitrogen in the root nodules of legumes?

    • A.Nitrosomonas
    • B.Rhizobium✓ Correct Answer
    • C.Nitrobacter
    • D.Pseudomonas

    Explanation: They live symbiotically in nodules.

12. Q12.Which gas is the major reservoir of nitrogen in the atmosphere?

    • A.Ammonia
    • B.Nitrous oxide
    • C.Nitrogen (N2)✓ Correct Answer
    • D.Nitric oxide

    Explanation: About 78 per cent of air is nitrogen.

13. Q13.The main process that removes carbon dioxide from the atmosphere is:

    • A.photosynthesis✓ Correct Answer
    • B.respiration
    • C.combustion
    • D.decomposition

    Explanation: Plants use CO2 to build sugars.

14. Q14.In aquatic ecosystems the pyramid of biomass is usually:

    • A.upright
    • B.spindle-shaped
    • C.inverted✓ Correct Answer
    • D.absent

    Explanation: Phytoplankton have small standing biomass but high turnover.

15. Q15.The largest functional unit of ecological organisation is the:

    • A.biosphere✓ Correct Answer
    • B.community
    • C.population
    • D.ecosystem

    Explanation: It includes all ecosystems of the Earth.

16. Q16.The scientific study of the relationship between organisms and their environment is called:

    • A.ethology
    • B.embryology
    • C.ecumenics
    • D.ecology✓ Correct Answer

    Explanation: Ernst Haeckel coined the term ecology.

17. Q17.Net primary productivity is equal to gross primary productivity minus:

    • A.decomposition
    • B.herbivory
    • C.photosynthesis
    • D.respiratory losses✓ Correct Answer

    Explanation: NPP = GPP - R.

18. Q18.The transition zone between two ecosystems is called the:

    • A.ecocline
    • B.ecotone✓ Correct Answer
    • C.niche
    • D.biome

    Explanation: Mangroves lie in an ecotone between sea and land.

19. Q19.The greater species diversity found at an ecotone is known as the:

    • A.bottleneck effect
    • B.edge effect✓ Correct Answer
    • C.founder effect
    • D.greenhouse effect

    Explanation: Species of both adjoining ecosystems occur there.

20. Q20.The trophic-dynamic concept of ecosystems was proposed by:

    • A.Raymond Lindeman✓ Correct Answer
    • B.A. G. Tansley
    • C.Ernst Haeckel
    • D.Eugene Odum

    Explanation: His 1942 paper introduced energy transfer between trophic levels.