Biology Class 12 NCERT Solutions: Chapter 14 Ecosystem Part 1

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Q.1 Fill in the blanks.

(a) Plants are called as_________ because they fix carbon dioxide.

(b) In an ecosystem dominated by trees, the pyramid (of numbers) is _________ type.

(c) In aquatic ecosystems, the limiting factor for the productivity is _________.

(d) Common detritivores in our ecosystem are_________.

(e) The major reservoir of carbon on earth is_________.

Answer:

(a) Plants are called as autotrophs because they fix carbon dioxide.

(b) In an ecosystem dominated by trees, the pyramid (of numbers) is of inverted type.

(c) In aquatic ecosystems, the limiting factor for productivity is light.

(d) Common detritivores in our ecosystem are earthworms.

(e) A major reservoir of carbon on Earth is oceans.

Q.2 Which one of the following has the largest population in a food chain?

(a) Producers

(b) Primary consumers

(c) Secondary consumers

(d) Decomposers

Answer:

(d) Decomposers

  • Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals.

Image of Food Chain

Image of Food Chain

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Q.3 The second trophic level in a lake is

(a) Phytoplankton

(b) Zooplankton

(c) Benthos

(d) Fishes

Answer:

(b) Zooplankton

  • Zooplankton are primary consumers in aquatic food chains that feed upon phytoplankton. Therefore, they are present at the second trophic level in a lake.

Image of Zooplankton

Image of Zooplankton

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