NEETAceToday's NEET Daily

Ecosystem patterns, components, productivity, decomposition, energy flow and pyramids: NEET MCQs with answers

106 questions on this topic of Ecology and Environment (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

Practise Ecology and Environment freeAll Ecology and Environment questions

Free with a Google sign-in; NEET Daily needs no sign-in at all.

easy

1. An ecosystem can be described as:

  1. A group of individuals of one species
  2. Only the non-living components of an area
  3. A single food chain
  4. A functional unit of nature where organisms interact among themselves and with their physical environment
Show answer and explanation

Answer: (D) A functional unit of nature where organisms interact among themselves and with their physical environment

An ecosystem is a functional unit of nature in which living organisms interact among themselves and with the surrounding physical environment. Crop fields and aquaria are man-made ecosystems.

NCERT Class 12

medium

2. Why is the measurement of biomass in terms of dry weight considered more accurate than fresh weight in ecological studies?

  1. Dry weight includes inorganic mineral ash that contributes directly to trophic energy transfer
  2. Fresh weight fluctuates drastically with continuous changes in water content
  3. Fresh weight cannot be measured using standard analytical laboratory balances
  4. Dry weight remains constant across different trophic levels within a food web
Show answer and explanation

Answer: (B) Fresh weight fluctuates drastically with continuous changes in water content

Biomass measured as dry weight is preferred because fresh weight varies widely with fluctuating moisture levels and environmental humidity. Dry weight reflects the actual organic matter synthesized and accumulated.

hard

3. If 1,000,000 J of incident sunlight falls on a forest canopy, what is the maximum amount of energy likely trapped as Net Primary Productivity (NPP), assuming plants capture 2% of incident solar radiation and consume 20% of GPP in respiration?

  1. 20,000 J
  2. 16,000 J
  3. 4,000 J
  4. 8,000 J
Show answer and explanation

Answer: (B) 16,000 J

Incident solar radiation = 1,000,000 J. Energy captured by plants (GPP) = 2% of 1,000,000 J = 20,000 J. Autotrophic respiration (R) = 20% of 20,000 J = 4,000 J. Therefore, NPP = GPP - R = 20,000 J - 4,000 J = 16,000 J.

medium

4. Read the following two statements: Statement I: The pyramid of biomass in sea is generally inverted because the biomass of fishes far exceeds that of phytoplankton. Statement II: Phytoplankton have a very high rate of turnover and short lifespan compared to predatory fishes. Choose the correct option:

  1. Both Statement I and Statement II are correct and Statement II explains Statement I.
  2. Statement I is correct but Statement II is incorrect.
  3. Statement I is incorrect but Statement II is correct.
  4. Both Statement I and Statement II are incorrect.
Show answer and explanation

Answer: (A) Both Statement I and Statement II are correct and Statement II explains Statement I.

The pyramid of biomass in the sea is generally inverted because the standing crop of phytoplankton (producers) at any given time is low compared to consumers (fishes), supported by the extremely high reproductive turnover and short life cycle of phytoplankton.

easy

5. If Autotrophs trap 9000 J of energy, the 10% law predicts the energy passed on to herbivores is about:

  1. 900 J
  2. 4500 J
  3. 90 J
  4. 8100 J
Show answer and explanation

Answer: (A) 900 J

By the 10% law, approximately 10% of producer energy is transferred: 0.1×9000 = 900 J.

Quick tip: About 10% is transferred to the next trophic level.

hard

6. Which of the following combinations of environmental factors will maximally promote the rate of decomposition of fallen litter?

  1. Submerged water-logged condition, cool temperature, and cellulose-rich detritus
  2. Anaerobic condition, low temperature (<10 °C), and lignin-rich detritus
  3. Dry soil condition, high temperature (>30 °C), and chitin-rich detritus
  4. High moisture, warm temperature (>25 °C), and nitrogen-rich detritus
Show answer and explanation

Answer: (D) High moisture, warm temperature (>25 °C), and nitrogen-rich detritus

Decomposition is an oxygen-requiring process. Warm and moist environments strongly favour decomposition, whereas low temperature and anaerobiosis inhibit it. Moreover, detritus rich in nitrogen and water-soluble substances decomposes much faster than detritus rich in lignin and chitin.

easy

7. Producers in an ecosystem fix 20000 J of energy. Following the 10% law, the energy available to tertiary consumers is:

  1. 200 J
  2. 2 J
  3. 20 J
  4. 5000 J
Show answer and explanation

Answer: (C) 20 J

Only about 10% passes to each higher trophic level. tertiary consumers are 3 transfers away: 20000 × 0.1³ = 20 J.

easy

8. Energy fixed by Autotrophs is 9000 J. Applying the 10% law, the energy available at the next trophic level (herbivores) is roughly:

  1. 900 J
  2. 90 J
  3. 8100 J
  4. 4500 J
Show answer and explanation

Answer: (A) 900 J

By the 10% law, approximately 10% of producer energy is transferred: 0.1×9000 = 900 J.

Quick tip: About 10% is transferred to the next trophic level.

easy

9. Identify the mismatched pair with respect to trophic levels in a terrestrial grassland ecosystem:

  1. Primary producer - Grasses
  2. Primary consumer - Grasshopper
  3. Tertiary consumer - Rabbit
  4. Secondary consumer - Frog
Show answer and explanation

Answer: (C) Tertiary consumer - Rabbit

In a terrestrial grassland ecosystem, rabbit is a herbivore and therefore occupies the second trophic level (primary consumer). Tertiary consumers are top carnivores such as snakes or hawks in this food chain.

hard

10. The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter. Of this, the oceans contribute only about:

  1. 120 billion tons
  2. 55 billion tons, despite covering about 70 per cent of the surface
  3. 10 billion tons
  4. 150 billion tons
Show answer and explanation

Answer: (B) 55 billion tons, despite covering about 70 per cent of the surface

Despite occupying about 70 per cent of the surface, the productivity of the oceans is only about 55 billion tons.

easy

11. If Green plants trap 18000 J of energy, the 10% law predicts the energy passed on to primary consumers is about:

  1. 16200 J
  2. 180 J
  3. 9000 J
  4. 1800 J
Show answer and explanation

Answer: (D) 1800 J

By the 10% law, approximately 10% of producer energy is transferred: 0.1×18000 = 1800 J.

Quick tip: About 10% is transferred to the next trophic level.

easy

12. Of the total incident solar radiation falling on the Earth, what proportion constitutes photosynthetically active radiation (PAR)?

  1. More than 80%
  2. Exactly 100%
  3. Between 60% and 75%
  4. Less than 50%
Show answer and explanation

Answer: (D) Less than 50%

NCERT states that of the total incident solar radiation, less than 50 per cent of it is photosynthetically active radiation (PAR). From this PAR, plants capture only 2-10 per cent.

Keep going with Ecology and Environment. All 340 questions with instant answers, your mistakes saved for revision and your accuracy by topic.
Start practising

Other topics in Ecology and Environment