CDS Practice questions for Ecology and Environment Part 13

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78. Which among the following are capable of fixing atmospheric nitrogen into ammonium ions?

1. Aerobic Azatobacter

2. Rhizobium

3. Nitrobacteria

4. Nitrosamines bacteria

Select the correct answer using the code given belowΛa) 1 and 2 only

(b) 3 and 4 only

© 1, 2 and 3 only

(d) 1, 2, 3 and 4

Answer: A

79. Consider the following pairs:

Aquatic Characteristics


1. Neutrons : Live at air- water


2. Periphytons : Ferr swimming


3. Nektons : Ferr floating

Organisms with

Limited powers of


4. Benthos : Live at the bottom

Of the water bodies

Which of the pairs given above is/are correct matched?

(a) 1, 2 and 3 only

(b) 1 and 4 only

(c) 2, 3 and 4 only

(d) 1, 2, 3 and 4

Answer: B

80. With reference to Stockholm Convention on persistent Organic Pollutants, co insider the following statements:

1. The convention is applicable only to twelve persistent organic pollutants referred to ‘Dirty Dozen’

2. It is under the framework of Intergovernmental Panel on Climate Change

3. It is legally binding its signatories. Which of the statements given above is/are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 3 only

(d) 1, 2 and 3

Answer: C

81. With reference to Keystone species, consider the following statements:

1. A. Keystone species exhibits disproportionably large effect on its environment. Relative to its abundance.

2. Figs in tropical rainforests are keystone species as they produce large quantity of fruits.

Select the correct answer using the code given below.

(a) 1only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: C

82. Arrange the following ecosystem sin the increasing order of their mean net primaaryproductivity.

1. Estuaries

2. Desert scrub

3. Open Ocean

4. Alpine ecosystem

Select the correct answer using the code given below

(a) 3-2-4-1

(b) 2-3-4-1

(c) 2-4-3-1

(d) 2-3-1-4

Answer: B

83. In which of the following season (s), growth of Phytoplankton is maximum in a fresh water lake?

(a) Winter

(b) Autumn

(c) Spring

(d) Both (b) and (c)

Answer: D

84. Which of the following best defines “edge effect”?

(a) It refers to the changes in population or community structures that occur at the boundary of two habitats.

(b) It refers to the changes in species composition at boundary between a terrestrial and aquatic habitat.

(c) It refers to the reduction in species variety at the edge of the Earth’s polar areas.

(d) It refers to the near extinction of a particular species owing to imbalances in a food web.

Answer: A