Ecology and Environment — NEET Botany MCQs with answers

Ecology and Environment is a Botany chapter in the NEET (UG) syllabus. NEET720 has 321 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.

Topics covered

Organisms and Populations · Ecosystem · Biodiversity and Conservation · Ecology and Environment · Organisms and Environment · Population Ecology · Community Ecology · Ecological Succession · Biogeochemical Cycles · Environmental Issues

8 free Ecology and Environment practice questions with answers

Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.

1. Question 1 · medium · Organisms and Populations

   Consider the following statements: (I) Exponential growth follows dN/dt = rN and gives a J-shaped curve. (II) Logistic growth follows dN/dt = rN(1-N/K), K being carrying capacity. (III) Logistic growth assumes unlimited resources. (IV) At N=K, dN/dt becomes zero. How many statements are correct?

   • A.One
   • B.Two
   • C.Three
   • D.Four
   Show answer and explanation

   Answer: C. Three

   I, II, IV correct; III is wrong — logistic growth assumes limited resources.

   Exponential growth (unlimited resources) gives a J-curve. Logistic growth is realistic with limited resources; at N=K, (1-N/K)=0 so dN/dt=0.

   Common mistake: Confusing resource assumptions of the two models

2. Question 2 · medium · Organisms and Populations

   Match the interactions with their effect notation (+ beneficial, - harmful, 0 neutral): Column I: (a) Commensalism (b) Amensalism (c) Parasitism (d) Protocooperation Column II: (i) +,+ (ii) +,0 (iii) -,+ (iv) -,0

   • A.a-ii, b-iv, c-iii, d-i
   • B.a-i, b-ii, c-iii, d-iv
   • C.a-iv, b-ii, c-i, d-iii
   • D.a-ii, b-iii, c-iv, d-i
   Show answer and explanation

   Answer: A. a-ii, b-iv, c-iii, d-i

   Commensalism +,0; Amensalism -,0; Parasitism -(host),+(parasite); Protocooperation +,+.

   Standard ecological interaction sign conventions place commensalism as (+,0), amensalism as (-,0), parasitism as (-,+), and protocooperation as (+,+).

   Common mistake: Confusing commensalism with mutualism signs

3. Question 3 · easy · Organisms and Populations

   Clownfish gain protection from predators among sea anemone tentacles while the anemone benefits from food scraps and improved water circulation caused by the fish. This is best classified as:

   • A.Mutualism
   • B.Commensalism
   • C.Parasitism
   • D.Amensalism
   Show answer and explanation

   Answer: A. Mutualism

   Both partners benefit, so it is mutualism.

   Since both the clownfish (protection) and anemone (food scraps, water circulation) benefit, the relationship is mutualism, not one-sided commensalism.

   Common mistake: Overgeneralizing this pair as commensalism without checking mutual benefit

4. Question 4 · medium · Organisms and Populations

   An age pyramid that is broad at the base and narrows sharply toward the top, with a small pre-reproductive base compared to reproductive and post-reproductive groups, indicates a population that is:

   • A.Declining
   • B.Expanding
   • C.Stable
   • D.Undergoing exponential growth
   Show answer and explanation

   Answer: A. Declining

   A small pre-reproductive base relative to other groups signals a declining population.

   Age pyramids with a large pre-reproductive base indicate expanding populations; a bell/urn shape with a narrow or small pre-reproductive base indicates declining populations; a pyramid with roughly equal pre-reproductive and reproductive groups indicates stability.

   Common mistake: Assuming all narrow-top pyramids represent growth

5. Question 5 · medium · Organisms and Populations

   Consider these statements about adaptations of organisms to environmental stress: (I) Kangaroo rats in deserts survive without drinking water by producing highly concentrated urine. (II) Seals in polar waters have a thick layer of blubber for insulation. (III) Some desert plants have CAM photosynthesis to reduce water loss. (IV) Amphibians in high mountains regulate body temperature entirely by internal metabolic heat production like mammals. How many statements are correct?

   • A.One
   • B.Two
   • C.Three
   • D.Four
   Show answer and explanation

   Answer: C. Three

   I, II, III correct; IV is wrong since amphibians are ectotherms/poikilotherms, not true endotherms.

   Kangaroo rats concentrate urine to conserve water. Seals use blubber for insulation. Desert plants like Opuntia use CAM pathway to minimize water loss via stomata opening at night. Amphibians are poikilotherms and cannot regulate body temperature internally like mammals; instead they behaviourally regulate (basking, burrowing).

   Common mistake: Assuming all animals can thermoregulate internally

6. Question 6 · medium · Organisms and Populations

   Succulent desert plants like Opuntia keep their stomata closed during the day and open at night. This adaptation primarily helps in:

   • A.Reducing transpirational water loss
   • B.Increasing the rate of photorespiration
   • C.Maximizing direct daytime CO2 fixation via Rubisco
   • D.Enhancing nitrogen fixation
   Show answer and explanation

   Answer: A. Reducing transpirational water loss

   Nocturnal stomatal opening in CAM plants minimizes water loss in hot, dry daytime conditions.

   CAM (Crassulacean Acid Metabolism) plants open stomata at night to fix CO2 into organic acids, storing it for use during the day when stomata remain closed, thereby drastically reducing daytime transpirational water loss — a key desert adaptation.

   Common mistake: Confusing CAM plants with C4 plants

7. Question 7 · medium · Ecosystem

   Gross Primary Productivity (GPP) of an ecosystem minus respiratory losses (R) by producers gives:

   • A.Net Primary Productivity
   • B.Secondary Productivity
   • C.Standing crop
   • D.Net Community Productivity
   Show answer and explanation

   Answer: A. Net Primary Productivity

   NPP = GPP − R (respiration by producers).

   Net Primary Productivity is the rate of biomass storage remaining after producers use some fixed energy for their own respiration, expressed as NPP = GPP − R.

   Common mistake: Confusing NPP with standing crop

8. Question 8 · medium · Ecosystem

   Arrange the steps of decomposition in the correct sequence: (I) Catabolism (II) Fragmentation (III) Leaching (IV) Humification (V) Mineralisation

   • A.II, III, I, IV, V
   • B.I, II, III, IV, V
   • C.III, II, I, V, IV
   • D.II, I, III, IV, V
   Show answer and explanation

   Answer: A. II, III, I, IV, V

   Correct order: fragmentation, leaching, catabolism, humification, mineralisation.

   Decomposition proceeds through detritivore-mediated fragmentation, water-soluble leaching, microbial catabolism (enzymatic breakdown), humification (formation of dark humus), and finally mineralisation (release of inorganic nutrients).

   Common mistake: Misordering catabolism relative to leaching

Questions about Ecology and Environment for NEET

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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (321 active practice questions in this chapter today).