Ecosystem – Ecosystem-Structure and Function: NEET MCQs with Answers

15 free questions on Ecosystem – Ecosystem-Structure and Function for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Ecosystem-Structure and Function, Patterns, components;

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Question 1

Previous-year question
Secondary succession takes place on/in [AIPMT 2015]
  1. a degraded forest
  2. a newly created pond
  3. newly cooled lava
  4. bare rock
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Answer: (A) a degraded forest
Explanation: Secondary succession begins in areas where a community previously existed but was destroyed by fire, flood, felling or cultivation. Soil, seeds and other propagules are still present, so the process is far faster than primary succession. Newly created ponds, freshly cooled lava and bare rock have no pre-existing soil or community and therefore support primary succession.

Question 2

Previous-year question
The term 'ecosystem' was coined by [NEET 2016]
  1. E.P. Odum
  2. A.G. Tansley
  3. E. Haeckel
  4. E. Warming
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Answer: (B) A.G. Tansley
Explanation: The British ecologist Sir Arthur G. Tansley coined the term 'ecosystem' in 1935. E.P. Odum later defined it as a functional unit of nature; Ernst Haeckel coined the term 'ecology', and Eugene Warming is regarded as a founder of plant ecology.

Question 3

Previous-year question
Which of the following is a characteristic feature of a cropland ecosystem? [NEET 2016]
  1. Absence of soil organisms
  2. Least genetic diversity
  3. Absence of weeds
  4. Ecological succession
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Answer: (B) Least genetic diversity
Explanation: A cropland is a man-made ecosystem in which a single high-yielding variety is grown over a large area (monoculture), so its genetic diversity is the lowest among ecosystems. Soil organisms and weeds are certainly present in croplands, and continuous human management prevents natural ecological succession from proceeding.

Question 4

Previous-year question
Vertical distribution of different species occupying different levels in a biotic community is known as [AIPMT 2015]
  1. stratification
  2. zonation
  3. pyramid
  4. divergence
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Answer: (A) stratification
Explanation: Stratification is the arrangement of the species of a community into distinct vertical layers; for example, in a forest the tall trees occupy the top canopy, shrubs form the middle storey and herbs and grasses the ground layer. Zonation is horizontal distribution along an environmental gradient.

Question 5

Previous-year question
An association of individuals of different species living in the same habitat and having functional interactions is called [AIPMT 2015]
  1. biotic community
  2. ecosystem
  3. population
  4. ecological niche
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Answer: (A) biotic community
Explanation: A biotic community is an assemblage of populations of different species that live together in a common habitat and interact functionally through food chains, competition, predation and mutualism. A population consists of individuals of only one species; an ecosystem is the community plus its abiotic environment; and a niche is the functional role of a species.

Question 6

Previous-year question
Most of the animals that live in deep oceanic waters are [AIPMT 2015]
  1. tertiary consumers
  2. secondary consumers
  3. detritivores
  4. primary consumers
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Answer: (C) detritivores
Explanation: Sunlight does not penetrate to the deep sea, so photosynthesis and hence producers are virtually absent there. Deep-sea animals therefore survive mainly on the dead organic matter, faecal pellets and carcasses that rain down from the productive surface layers; such organisms that feed on detritus are called detritivores.

Question 7

Previous-year question
Decomposers are organisms that [AIPMT 1994]
  1. elaborate chemical substances, causing death of tissues
  2. operate in a living body, simplifying organic substances of cells step by step
  3. attack and kill plants as well as animals
  4. operate in relay terms, simplifying step by step the organic constituents of a dead body
Show answer
Answer: (D) operate in relay terms, simplifying step by step the organic constituents of a dead body
Explanation: Decomposers (fungi, bacteria and actinomycetes) are microconsumers or saprotrophs that secrete digestive enzymes on to dead organic remains and absorb the simple products. They act in a relay, one group breaking down what the previous group has partly digested, thus converting complex organic constituents of dead bodies and wastes into simple soluble inorganic forms that re-enter the nutrient pool.
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Question 8

Previous-year question
Which of the following is the most stable ecosystem? [AIPMT 1995]
  1. Forest
  2. Desert
  3. Mountain
  4. Ocean
Show answer
Answer: (D) Ocean
Explanation: The ocean is regarded as the most stable ecosystem because of its enormous size, its resilience to disturbance and its ability to maintain ecological balance over long periods. Ocean stability is a major regulator of global climate, controlling heat, carbon, nutrients and dissolved gases exchanged between the upper and lower layers of water.

Question 9

Previous-year question
What is true of an ecosystem? [AIPMT 1998]
  1. Primary consumers are least dependent upon producers
  2. Primary consumers out-number producers
  3. Producers are more numerous than primary consumers
  4. Secondary consumers are the largest and most powerful
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Answer: (C) Producers are more numerous than primary consumers
Explanation: In most ecosystems the producers (green plants and algae) are far more numerous and possess much more biomass than the primary consumers (herbivores). Producers form the base of the food chain and support the entire ecosystem, because only about 10% of the energy at one trophic level passes to the next.

Question 10

Previous-year question
Which one of the following is NOT a functional unit of an ecosystem? [AIPMT 2012]
  1. Energy flow
  2. Decomposition
  3. Productivity
  4. Stratification
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Answer: (D) Stratification
Explanation: The four functional aspects of an ecosystem are productivity, decomposition, energy flow and nutrient cycling. Stratification — the vertical distribution of different species occupying different levels, such as trees, shrubs and herbs in a forest — is a structural, not a functional, attribute.

Question 11

Previous-year question
Which one of the following is a characteristic feature of a cropland ecosystem? [NEET 2016, Phase-II]
  1. Least genetic diversity
  2. The absence of weeds
  3. Ecological succession
  4. The absence of soil organisms
Show answer
Answer: (A) Least genetic diversity
Explanation: A cropland is the largest man-made (anthropogenic) ecosystem, characterised by a monoculture of a single crop variety and hence by very low species and genetic diversity, coupled with high productivity. Weeds and soil organisms are certainly present, and succession is prevented by continuous human management.

Question 12

Previous-year question
The term 'ecosystem' was coined by [NEET 2016, Phase-I]
  1. A.G. Tansley
  2. E. Haeckel
  3. E. Warming
  4. E.P. Odum
Show answer
Answer: (A) A.G. Tansley
Explanation: The term ecosystem was coined by A.G. Tansley in 1935. An ecosystem is a self-regulating and self-sustaining structural and functional unit of nature consisting of all the living beings of an area together with their physical environment. Haeckel coined the term 'ecology' and Odum popularised ecosystem ecology.

Question 13

Previous-year question
Quercus species are the dominant component of [2008]
  1. scrub forests
  2. temperate deciduous forests
  3. tropical rainforests
  4. alpine forests
Show answer
Answer: (B) temperate deciduous forests
Explanation: The oaks dominate the temperate deciduous forests of the northern hemisphere, shedding their leaves before winter to avoid frost damage and water loss when the soil water is frozen.

Question 14

Previous-year question
Which of the following is the most stable ecosystem? [1995]
  1. Mountain
  2. Forest
  3. Ocean
  4. Desert
Show answer
Answer: (C) Ocean
Explanation: The ocean is vast, ancient and buffered against fluctuation, its temperature, salinity and chemistry altering only slowly. This constancy makes it the most stable of the major ecosystems, while deserts are subject to extreme variation.

Question 15

Previous-year question
A lake near a village suffered heavy mortality of fishes within a few days. Which is the most likely explanation? [2008]
  1. The lake water turned green and stinking
  2. Large amounts of urea and phosphate fertiliser were used in the fields nearby
  3. Phytoplankton populations in the lake declined initially
  4. The area was sprayed with DDT from an aircraft
Show answer
Answer: (A) The lake water turned green and stinking
Explanation: The key selects the observation of green stinking water, which indicates a dense algal bloom whose decay has stripped the water of oxygen. The fertiliser run-off named in option (2) is the underlying cause of that bloom.

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