Free Man and His Environment MCQs with Answers

91. Which of the following is correct for r­-selected species?

• A. Large number of progeny with small size.
• B. Large number of progeny with large size.
• C. Small number of progeny with small size.
• D. Small number of progeny with large size.

Explanation: Organisms that are r-­selected (r­-strategists) are able to colonize a habitat rapidly, utilizing the food and other resources before other organisms are established and begin to compete. The r­-strategists tend to be relatively small organisms with short life spans (e.g., bacteria) and often live in temporary or unstable environments; characteristically their survival depends on their ability to produce large numbers of offspring rather than on their ability to compete.

92. If a '+' sign is assigned to a beneficial interaction, a '-' sign to a detrimental and an 'O' sign to a neutral interaction, then the population interaction represented by '+' '-' refers to

• A. Mutualism
• B. Amensalism
• C. Commensalism
• D. Parasitism

Explanation: Parasitism is an association in which one organism (the parasite) lives on (ectoparasitism) or in (endoparasitism) the body of another organism (host), from which it obtains its nutrients. This association is beneficial for the parasites as they get continuous supply of nutrients from their host and are able to rapidly multiply their numbers. But it is detrimental for the host organism as parasitic infection leads to various complications and diseases in the host body may also be fatal to him under certain circumstances.

93. It is much easier for a small animal to run uphill than for a large animal, because:

• A. Small animals have a lower O2 requirement
• B. The efficiency of muscles in large animals is less than in the small animals.
• C. It is easier to carry a small body weight
• D. Smaller animals have a higher metabolic rate

Explanation: The small animals have a smaller surface area to body volume ratio. They have higher metabolic rates than larger animals. Therefore, it is much easier for small animals to move uphill than large animals. The ease of running uphill also depends on the animal's energy efficiency. Smaller animals may have an advantage in terms of energy expenditure, but larger animals can compensate with their strength and endurance.

94. The principle of competitive exclusion was stated by:

• A. C. Darwin
• B. G.F. Gause
• C. Mac Arthur
• D. Verhulst and Pearl

Explanation: Two or more species with closely similar niche requirements cannot exist indefinitely in the same area as sooner or later they come into competition for possession of it. This is called Gause's competitive exclusion principle, which states that an ecological niche cannot be simultaneously and completely occupied by established populations of more than one species. Two species can live in the same habitat but not in the same niche. The more similar the two niches are, the more severe the competition is.

95. Gause's principle of competitive exclusion states that:

• A. No two species can occupy the same niche indefinitely for the same limiting resources.
• B. Larger organisms exclude smaller ones through competition
• C. More abundant species will exclude the less abundant species through competition.
• D. Competition for the same resources exclude species having different food preferences.

Explanation: Two or more species with closely similar niche requirements cannot exist indefinitely in the same area as sooner or later they come into competition for possession of it. This is called Gause's competitive exclusion principle, which states that an ecological niche cannot be simultaneously and completely occupied by established populations of more than one species. Two species can live in the same habitat but not in the same niche. The more similar the two niches are, the more severe the competition is.

96. In which of the following interactions both partners are adversely affected?

• A. Parasitism
• B. Mutualism
• C. Competition
• D. Predation

Explanation: Competition in ecology refers to the interaction between two or more species that share a common limiting resource, such as food, territory, or other essential resources. This interaction can have significant effects on the populations and ecological dynamics of the competing species.

97. An association of individuals of different species living in the same habitat and having functional interactions is:

• A. Ecosystem
• B. Population
• C. Ecological niche
• D. Biotic community

Explanation: Biological or biotic community is an assemblage of populations of different species of plants, animals, bacteria and fungi which live in a particular area and interact with one another through competition, predation, mutualism, etc. Each biotic community has a specific composition and structure,e.g., pond community.

98. The following graph depicts changes in two populations (A and B) of herbivores in a grassy field. A possible reason for these changes is that:

• A. Population A produced more offspring than population B.
• B. Population A consumed the members of population B.
• C. Both plant populations in this habitat decreased.
• D. Population B competed more successfully for food than population A.

Explanation: Both the populations are herbivorous, thus they cannot affect each other. If the food sources for these populations A and B have decreased, then both the populations A and B would have declined. If population A has produced more offspring, then the graph of A should have increased. Based on the graph, population B is more successful in competing with population A, that is why the number of organisms in population B increased while that in population A decreased, as they get access to limited resources.

99. Besides paddy fields, cyanobacteria are also found inside the vegetative part of the:

• A. Equisetum
• B. Psilotum
• C. Pinus
• D. Cycas

Explanation: Coralloid roots of Cycas have a symbiotic association with blue­-green algae like Nostoc and Anabaena. Coralloid roots are irregular, negatively geotropic, dichotomously branched coral-like roots which do not possess root hairs and root caps.

100. A sedentary sea anemone gets attached to the shell lining of a hermit crab. This association is known as:

• A. Commensalism
• B. Amensalism
• C. Ectoparasitism
• D. Symbiosis

Explanation: Sea anemone gets associated with the shell of a hermit crab. It provides camouflage and protection to the crab due to the presence of stinging cells in the sea anemone. In turn, the sea anemone is transported to new places reaching new food sources.This is symbiosis as both the organisms are benefitted.