Free Man and His Environment MCQs with Answers

101. A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is

• A. 05
• B. zero
• C. 10
• D. 15

Explanation: Natality and immigration positively contribute to the population growth while mortality and emigration are negative factors. In the given question, The net increase in population is natality + immigration = 250 + 20 = 270 The net decrease in population is mortality + emigration = 240 + 30 = 270 Thus, net increase in population = 270 - 270 = 0

102. An age pyramid with a broad base indicates a:

• A. High percentage of old individuals.
• B. Low percentage of young individuals.
• C. Stable population.
• D. High percentage of young individuals.

Explanation: An age pyramid is a graphic representation of an abundance of individuals of different age groups with pre-­reproductive individuals at the base, reproductive individuals in the middle and post­-reproductive individuals at the top. A triangular age pyramid has a high proportion of pre­-reproductive individuals, moderate number of reproductive individuals and fewer post­-reproductive individuals. It represents a young or rapidly growing population. In a bell­-shaped age pyramid, the number of pre­-reproductive and reproductive individuals is almost equal. Post-reproductive individuals are comparatively fewer. It represents a stable or stationary population where growth rate is nearly zero. In an urn­-shaped age pyramid, the number of reproductive individuals is higher than the number of pre­-reproductive individuals. It represents a declining or diminishing population.

103. Benthic organisms are affected the most by:

• A. Light reaching the forest floor.
• B. Surface turbulence of water.
• C. Sediment characteristics of aquatic ecosystems.
• D. Water­holding capacity of soil.

Explanation: Benthic organisms, which are organisms that live on or near the bottom of aquatic ecosystems (such as oceans, rivers, and lakes) .Benthic organisms are bottom dwelling forms found crawling or attached to the bottom. The sediment characteristics often determine the type of benthic animals that can thrive there.

104. Cuscuta is an example of:

• A. Ectoparasitism
• B. Brood parasitism
• C. Predation
• D. Endoparasitism

Explanation: Cuscuta is a total stem parasite which is a good example of ectoparasitism. It is commonly found growing on hedge plants. It has lost chlorophyll and leaves in the course of evolution. It attaches and wraps itself around the stem of the host plant and produces haustoria that gets inserted into the vascular system of the host. The parasitic plant sucks all the nutrients from the host plant with the help of haustoria. Cuscuta is known to receive even the flower inducing hormone or florigen from the host.

105. What type of human population is represented by the following age pyramid?

• A. Vanishing population
• B. Stable population
• C. Declining population
• D. Expanding population

Explanation: An age pyramid is a graphic representation of an abundance of individuals of different age groups with pre-­reproductive individuals at the base, reproductive individuals in the middle and post­-reproductive individuals at the top. A triangular age pyramid has a high proportion of pre­-reproductive individuals, a moderate number of reproductive individuals and fewer post­-reproductive individuals. It represents a young or rapidly growing population. In a bell­-shaped age pyramid, the number of pre­-reproductive and reproductive individuals is almost equal. Post-reproductive individuals are comparatively fewer. It represents a stable or stationary population where the growth rate is nearly zero. In an urn­-shaped age pyramid, the number of reproductive individuals is higher than the number of pre­-reproductive individuals. It represents a declining or diminishing population.

106. Large woody vines are more commonly found in

• A. Temperate forests
• B. Mangroves
• C. Tropical rainforests
• D. Alpine forests

Explanation: Lianas are large, climbing and woody vines that drape tropical rainforest trees. They have adapted to life in the rainforest by having their roots in the ground and climbing high onto the tree canopy to reach available sunlight. Many lianas start life in the rainforest canopy and send roots down to the ground. Tropical rainforests are lush, dense, and biodiverse ecosystems characterized by high annual rainfall and consistently warm temperatures. They are found near the equator in regions of Central and South America, Africa, Southeast Asia, and the Pacific Islands. Tropical rainforests are some of the most complex and ecologically rich environments on Earth.

107. Which one of the following is categorised as a parasite in its true sense?

• A. The female Anopheles bites and sucks blood from humans.
• B. Human foetus developing inside the uterus draws nourishment from the mother.
• C. Head louse living on the human scalp as well as laying eggs on human hair.
• D. The cuckoo (koel) lays its eggs in crow's nest.

Explanation: Parasitism is an association in which one organism (the parasite) lives on (ectoparasitism) or in (endoparasitism) the body of another (the host), from which it obtains its nutrients. They also produce vast numbers of eggs there e.g., head lice living on the human scalp.

108. Which one of the following is one of the characteristics of a biological community?

• A. Stratification
• B. Natality
• C. Mortality
• D. Sex-­ratio

Explanation: The characteristics of a biological community are dominance, species diversity, trophic organization, stratification, dynamism and stability. Organisms are not uniformly distributed throughout a community. They usually occur in definite zones.This spatial arrangement of populations is called stratification. Structurally, a community may be divided horizontally into sub-communities. This horizontal division constitutes the zonation in the community. Natality, mortality, age structure and sex ratio are the basic characteristics of a population.

109. Which one of the following is most appropriately defined?

• A. A host is an organism which provides food to another organism.
• B. An amensalism is a relationship in which one species is benefitted whereas the other is unaffected.
• C. A predator is an organism that catches and kills other organisms for food
• D. A parasite is an organism that always lives inside the body of another organism and may kill it.

Explanation: Predation is an interaction between members of two species in which members of one species capture, kill and eat up members of other species. Host is a term which is specifically related to parasitism. Amensalism is an interspecies interaction in which one species is harmed whereas the other one is unaffected. Parasitic organism can live both over the surface of their host or inside their body.

110. Quercus species are the dominant component in:

• A. Scrub forests
• B. Tropical rain forests
• C. Temperate deciduous forests
• D. Alpine forests.

Explanation: Quercus is the scientific genus name for oak trees, a diverse group of hardwood trees found in various regions around the world. There are over 600 species of oak trees within the Quercus genus, making it one of the most widespread and diverse tree genera. Oak trees are known for their valuable wood, acorns (nuts), and ecological importance. Temperate deciduous forests are ecosystems characterized by a specific type of vegetation and climate. These forests are found in regions with distinct seasons, including warm summers and cold winters. These forests have been historically important for timber production and continue to be harvested for wood products. The dominant trees in temperate deciduous forests are deciduous, which means they lose their leaves in the fall and remain bare during the winter.