51. Underground rivers are called:
Answer: C. aquifers
Biology Class 11 Unit 15: Ecology MCQs
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52. Bodies of living organisms are roughly ... water:
Answer: C. 70 percent
53. The percolation of water into the soil refers to:
Answer: B. water sinking into the ground
54. Nitrogen is needed for the synthesis of:
Answer: C. amino acids, nucleic acids and proteins
55. The processes of the nitrogen cycle include:
Answer: B. ammonification, nitrification, nitrogen fixation, assimilation and denitrification
56. The production of ammonia from decomposition of organic matter is:
Answer: B. ammonification
57. Ammonification is done by:
Answer: B. saprophytic soil bacteria and fungi
58. Nitrification is the conversion of ammonia to:
Answer: C. nitrates
59. Nitrosomonas converts:
Answer: B. ammonia to nitrites
60. Nitrobacter converts:
Answer: B. nitrites to nitrates
61. Nitrification takes place in:
Answer: B. well aerated soils, as the bacteria are aerobic
62. Nitrogen gas is chemically unreactive due to:
Answer: B. a very strong triple bond between two atoms
63. Fixation of nitrogen by lightning is:
Answer: C. atmospheric fixation
64. Atmospheric fixation accounts for about:
Answer: B. 5 to 8 percent
65. Synthesis of nitrogen fertilizers is:
Answer: C. industrial fixation
66. Biological nitrogen fixation fixes about:
Answer: C. 60 percent of nitrogen
67. Nitrogen-fixing bacteria convert atmospheric nitrogen to:
Answer: C. ammonia
68. A free-living aerobic nitrogen fixing bacterium is:
Answer: C. Azotobacter
69. A free-living anaerobic nitrogen fixing bacterium is:
Answer: B. Clostridium
70. A symbiotic nitrogen fixer in legumes is:
Answer: C. Rhizobium
71. Assimilation in the nitrogen cycle is:
Answer: B. utilization of nitrogen compounds in living bodies
72. Plants obtain nitrogen mostly as:
Answer: C. nitrates
73. Animals obtain nitrogen from:
Answer: C. eating plants or other animals
74. Denitrification is the:
Answer: B. conversion of nitrates back to nitrogen gas by denitrifying bacteria
75. A denitrifying bacterium is:
Answer: C. Pseudomonas
76. Denitrification occurs in the:
Answer: B. absence of oxygen
77. The sequence of replacement of one community by another in an area is:
Answer: B. ecological succession
78. Primary succession occurs on:
Answer: B. an area not previously inhabited, like bare rock or new lava
79. Secondary succession occurs where:
Answer: B. soil is already present after a disturbance, like fire or flood
80. An abandoned field reverting to forest is an example of:
Answer: B. secondary succession
81. Succession in water bodies, such as ponds and lakes, is:
Answer: B. hydrarch (hydrosere)
82. Succession on bare rock, sand dunes and dry areas is:
Answer: A. xerarch (xerosere)
83. The first species to colonize a bare area are called:
Answer: B. pioneer species
84. The intermediate communities in succession are called:
Answer: C. seral communities
85. The final stable community is the:
Answer: C. climax community
86. The pioneer stage of xerarch succession on bare rock is:
Answer: C. crustose lichen stage
87. Crustose lichens help in succession by:
Answer: B. secreting acids that decompose the rock and forming soil
88. The second stage of xerarch succession is the:
Answer: B. foliose lichen stage
89. Which are crustose lichens?
Answer: C. Lecanora and Rhizocarpon
90. The stage following the lichen stages is the:
Answer: C. moss stage
91. The correct sequence in xerarch succession is:
Answer: B. crustose lichen, foliose lichen, moss, herb, shrub, tree
92. Which stage precedes the shrub stage in xerarch succession?
Answer: B. Herb stage
93. In the climax stage of xerarch succession on a rock, the final trees are:
Answer: B. mesophytic
94. Population dynamics studies:
Answer: B. changes in numbers and structure of populations over time
95. Population size increases by:
Answer: B. births and immigration
96. Population size decreases by:
Answer: C. predation, natural deaths, culling, accidents and emigration
97. The characteristics of a population are:
Answer: B. growth, density, distribution, carrying capacity and viable size
98. An increase in the number of individuals of a population is:
Answer: B. population growth
99. A population with unlimited resources shows:
Answer: B. exponential growth after a lag phase
100. Population density is:
Answer: B. number of individuals per unit area or volume
About Biology Class 11 Unit 15 MCQs (Federal Board)
These 196 Biology MCQs cover Class 11 Unit 15: Ecology of the Federal Board (FBISE) HSSC-I (1st Year / Class 11) syllabus. They are SLO-based MCQs as per the new pattern for FBISE exams. Each question has four options and the correct answer is shown, so you can practise for the annual examination and find the topics you still need to revise. The questions are split over 4 pages of 50. Use the Print button to save this chapter as a PDF.