EXERCISES

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_________.

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

(a) Producers

(b) Primary consumers

(c) Secondary consumers

(d) Decomposers

3. The second trophic level in a lake is

(a) Phytoplankton

(b) Zooplankton

(c) Benthos

(d) Fishes

4. Secondary producers are

(a) Herbivores

(b) Producers

(c) Carnivores

(d) None of the above

5. What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?

(a) 100%

(b) 50 %

(c) 1-5%

(d) 2-10%

6. Distinguish between

(a) Grazing food chain and detritus food chain

(b) Production and decomposition

(c) Upright and inverted pyramid

(d) Food chain and Food web

(e) Litter and detritus.

7. Describe the components of an ecosystem.

8. Define ecological pyramids and describe with examples, pyramids of number and biomass.

9. What is primary productivity? Give brief description of factors that affect primary productivity.

10. Define decomposition and describe the processes and products of decomposition.

11. Give an account of energy flow in an ecosystem.

12. Write important features of a sedimentary cycle in an ecosystem.

13. Outline salient features of carbon cycling in an ecosystem.

Q.1 Decomposers like fungi and bacteria are

(i) autotrophs     (ii) heterotrophs
(iii) saprotrophs  (iv) chemo-autotrophs

Choose the correct answer

(a) (i) and (iii)

(b) (i) and (iv)

(c) (i) and (iii)

(d) (i) and (ii)

Q.2 The process of mineralization by microorganisms helps in the release of

(a) inorganic nutrients from the humus

(b) both organic and inorganic nutrients from detritus

(c) organic nutrients from the humus

(d) inorganic nutrients from detritus and formation of humus.

3 Productivity is the rate of production of biomass expressed in terms of

$$\begin{gathered} \left(\mathrm{i}\right) \left(\mathrm{kcal} {\mathrm{m}}^{-3}\right) {\mathrm{yr}}^{-1} \left(\mathrm{ii}\right) {\mathrm{g}}^{-2} {\mathrm{yr}}^{-1} \\ \left(\mathrm{iii}\right) {\mathrm{g}}^{-1} {\mathrm{yr}}^{-1} \left(\mathrm{iv}\right) \left(\mathrm{kcal} {\mathrm{m}}^{-2}\right) {\mathrm{yr}}^{-1} \end{gathered}$$

(a) (ii)

(b)(iii)

(c) (ii) and (iv)

(d) (i) and (iii)

4 An inverted pyramid of biomass can be found in which the ecosystem?
Marine

(a) Forest

(b) Marine

(c) Grassland

(d) Tundra

5 Which of the following is not a producer?

(a) Spirogyra

(b) Agaricus

(c) Volvox

(d) Nostoc

Q.6 Which of the following ecosystems is most productive in terms of net primary production?

(a) Deserts

(b) Tropical rain forests

(c) Oceans

(d) Estuaries

Q.7 Pyramid of numbers is

(a) Always upright

(c) Either upright or inverted

(b) Always inverted

(d) Neither upright nor inverted

Q.8 Approximately how much of the solar energy that falls on the leaves of the plant is converted to chemical energy by photosynthesis?

(a) Less than 1%

(b) 2-10%

(c) 30%

(d) 50%

Q.9 Among the following where do you think the process of decomposition would be the fastest?

(a) Tropical rain forest

(b) the Antarctic

(c) Dry arid region

(d) Alpine region

Q.10 How much of the net primary productivity of a terrestrial ecosystem eaten and digested by herbivores?

(a) 1%

(b) 10%

(c) 40%

(d) 90%