Chapter Wise Ecology & Environment MCQ’s With Explanation

Today’s Topic:Ecosystem: Structure and Function

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Today’s Topic:Ecosystem: Structure and Function

Q1. Consider the following statements:

  1. The term ecosystem was coined by Sir Arthur Tansley in 1935.
  2. Ecosystems can be recognized as self-regulating and self-sustaining units of a landscape.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                        d) Neither 1 nor 2

Ans:     C

Ecosystems are parts of nature where living organisms interact amongst themselves and with their physical environment. The term ecosystem was coined by Sir Arthur Tansley in 1935. Ecosystems vary greatly in sizes, such as the small pond or large forest. Ecosystems can be recognized as self-regulating and self-sustaining units of the landscape.

Q2. Which of the following are terrestrial ecosystems?

  1. Forests                      2. Ponds                      3. GrasslandsLakes                      5. Deserts

a) Only 1, 2 and 3                       b) Only 1, 3 and 5                      c) Only 2, 4 and 5                    d) 1, 2, 3 and 4

Ans:     B

Explanation:    In nature two major categories of ecosystems may be distinguished: terrestrial and aquatic. Forests, grasslands, and deserts are examples of terrestrial ecosystems. The aquatic ecosystems can be either fresh water i.e. ponds, lakes, streams or salt-water i.e. marine, estuaries.

Q3. Which of the following are aquatic ecosystems?

  1. Forests                      2. Ponds                      3. Streams                      4. Estuaries

a) Only 1, 2 and 3                      b) Only 1, 4 and 4                      c) Only 2, 3 and 4                      d) 1, 2, 3 and 4

Ans:     C

Explanation:    Ecosystems are parts of nature where living organisms interact amongst themselves and with their physical environment. In nature, two major categories of ecosystems may be distinguished terrestrial and aquatic. Forests grasslands and deserts are examples of terrestrial ecosystems. The aquatic ecosystems can be either freshwater (ponds, lakes, streams) or salt-water (marine, estuaries) type.

Q4. Consider the following statements:

  1. Marine and estuaries are freshwater ecosystems.
  2. Spacecraft and aquariums are man-made ecosystems.

Which of the statements given above is/are correct?

a) Only 1                       b) Only 2                      c) Both 1 and 2                        d) Neither 1 nor 2

Ans:     B

Explanation:    In nature, two major categories of ecosystems, may be distinguished: terrestrial and aquatic. Forests or grasslands and deserts are examples of terrestrial ecosystems. The aquatic ecosystems can be either fresh water or salt-water type. Ponds, lakes, and streams are freshwater ecosystems whereas marine and estuaries are salt-water ecosystems. Human activities may modify or convert natural ecosystems into anthropogenic or man-made ecosystems. Spacecraft and aquariums are considered as man-made ecosystems.

Q5. Consider the following statements:

  1. The food of consumers consists of organic compounds produced by other living organisms.
  2. Bacteria and fungi are decomposers living on dead organic matter or detritus.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                        d) Neither 1 nor 2

Ans:     C

Explanation:    Consumers are heterotrophic organisms mostly animals which generally ingest or swallow their food. The food of consumers consists of organic compounds produced by other living organisms.Decomposers are other heterotrophic organisms consisting mostly of bacteria and fungi which live on dead organic matter or detritus.

Q6. Match the following:

List-I                                        List-II

  1. Producer                                    1. Bacteria
  2. Primary Consumer                     2. Phytoplankton
  3. Secondary Consumer                3. Herbivore
  4. Decomposers                             4. Carnivore

Ans:     D

Explanation:    Producers are autotrophic, produce their own food by fixing light energy in the presence of simple inorganic abiotic substances. In deep aquatic ecosystems, floating microscopic plants called phytoplankton are the major aurotrophs.A consumer which derives nutrition by eating plants is called primary consumer or herbivore. The secondary consumer or carnivore is an animal that devours the flesh of herbivore or other animals.Decomposers are heterotrophic organisms consisting mainly of bacteria and fungi which live on dead organic matter or detritus.

Q7. Consider the following statements:

  1. Carnivores found the first trophic level and producers found the third trophic level.
  2. The biomass of a species is expressed in terms of either fresh or dry weight.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                       d) Neither 1 nor 2

Ans:     B

Explanation:    Ecosystem structure can also be expressed through food relationships of producers and consumers. Trophic (food) structure of an ecosystem is based on the existence of several trophic levels in the ecosystem. The producers form the first trophic level, herbivores the second, and carnivores constitute the third. The trophic structure may be described in terms of the amount of living material, called standing crop, present in different trophic levels at a given time. The standing crop is commonly expressed as the number of the biomass of organisms per unit area. The biomass of a species is expressed in terms of either food or dry weight.

Q8. Consider the following statements:

  1. The amounts of nutrients, such as nitrogen, phosphorous and calcium present in the soil at any given time is referred to as the standing state.
  2. The standing states of nutrients are the same from one ecosystem to another.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                       d) Neither 1 nor 2

Ans:     A

Explanation:    Nutrients necessary for the growth of living organisms are accumulated in the biomass and in abiotic components like soil. The amounts of nutrients, such as nitrogen, phosphorous and calcium present in the soil at any given time is referred to as the standing state. The standing states of nutrients differ from one ecosystem to another, or with seasons even in the same ecosystem.

Q9. Consider the following statements:

  1. Dead plant parts and animal remains are called detritus.
  2. If decomposition is stopped large amounts of a partially decomposed organic matter shall accumulate in the ecosystem.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                        d) Neither 1 nor 2

Ans:     C

Explanation:    Dead plant parts and animal remains are called detritus. Dead plant parts, like leaves, barks, flowers, etc., and dead remains of animals, including fecal matter, drop over the soil and constitute the above ground detritus, with the passage of time decomposing detritus loses weight until it disappears completely. If decomposition is retarded or stopped, large amounts of partially decomposed organic matter shall accumulate in the ecosystem.

Q10. Consider the following statements:

  1. The rate of decomposition of detritus is primarily regulated by the climatic factors and the chemical quality of detritus.
  2. Detritus decomposes gradually in a climate characterized by higher temperatures.

Which of the statements given above is/are correct?

a) Only 1                      b) Only 2                      c) Both 1 and 2                        d) Neither 1 nor 2

Ans:     A

Explanation:    The rate of decomposition of detritus is primarily regulated by the climatic factors and the chemical quality of detritus. Amongst climatic factors, the key role is played by temperature and soil moisture through their regulatory effect on the activities of soil microbes. Detritus decomposes very rapidly within a few weeks or months, in a climate characterized by higher temperature and moist conditions.

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