Question 41:
What is “ecological efficiency”?
(A) The ability of an ecosystem to recover after a disturbance
(B) The percentage of energy transferred from one trophic level to the next
(C) The rate of primary productivity in an ecosystem
(D) The biomass produced at each trophic level
Answer: (B) The percentage of energy transferred from one trophic level to the next
Explanation:
Ecological efficiency refers to the percentage of energy transferred from one trophic level to the next in an ecosystem. Typically, only about 10% of the energy at one level is passed on to the next, while the rest is lost as heat or used in metabolism.
Question 42:
What is the primary function of nitrifying bacteria in the nitrogen cycle?
(A) Fixing atmospheric nitrogen
(B) Converting ammonia into nitrites and nitrates
(C) Denitrification of nitrates into nitrogen gas
(D) Decomposition of dead organisms
Answer: (B) Converting ammonia into nitrites and nitrates
Explanation:
Nitrifying bacteria play a crucial role in the nitrogen cycle by converting ammonia (NH₃) into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), which plants can absorb and use. This process is called nitrification.
Question 43:
Which of the following is an example of secondary succession?
(A) A forest growing in an area after a volcanic eruption
(B) The formation of a pond in a barren land
(C) Regrowth of vegetation in a forest after a fire
(D) Lichens growing on bare rock
Answer: (C) Regrowth of vegetation in a forest after a fire
Explanation:
Secondary succession occurs in areas where a disturbance (like fire, flood, or human activity) has removed the existing vegetation but left the soil intact. The regrowth of vegetation in a forest after a fire is a classic example. Primary succession, on the other hand, occurs in areas without preexisting soil, such as after a volcanic eruption.
Question 44:
In which of the following ecosystems would you expect to find the highest species diversity?
(A) Desert
(B) Tundra
(C) Tropical rainforest
(D) Temperate grassland
Answer: (C) Tropical rainforest
Explanation:
Tropical rainforests have the highest species diversity of any ecosystem due to their warm, moist climate and consistent energy input from sunlight, which supports a wide variety of organisms. Deserts, tundras, and grasslands have less favorable conditions for such biodiversity.
Question 45:
Which of the following is an example of biological magnification?
(A) An increase in the size of fish populations in a lake
(B) Accumulation of DDT in the tissues of top-level predators
(C) The gradual buildup of minerals in the soil
(D) Growth of bacteria in water due to pollution
Answer: (B) Accumulation of DDT in the tissues of top-level predators
Explanation:
Biological magnification refers to the increasing concentration of toxic substances, such as DDT or mercury, in organisms at higher trophic levels. As top predators consume contaminated prey, the concentration of these toxins becomes higher in their tissues.
Question 46:
What is “gross primary productivity” (GPP)?
(A) The total amount of energy stored in an ecosystem
(B) The total amount of energy captured by photosynthesis in a given time
(C) The energy available to primary consumers
(D) The amount of energy lost as heat in an ecosystem
Answer: (B) The total amount of energy captured by photosynthesis in a given time
Explanation:
Gross primary productivity (GPP) is the total amount of energy captured by plants through photosynthesis. It represents the rate at which producers in an ecosystem convert solar energy into chemical energy.
Question 47:
Which of the following describes net primary productivity (NPP)?
(A) Energy lost as heat by plants
(B) Energy used by plants for respiration
(C) The energy remaining after respiration that is available for growth and reproduction
(D) The total energy captured by plants during photosynthesis
Answer: (C) The energy remaining after respiration that is available for growth and reproduction
Explanation:
Net primary productivity (NPP) is the energy that remains after plants have used some of the captured energy for respiration. NPP represents the amount of energy available for growth, reproduction, and consumption by herbivores.
Question 48:
Which of the following statements about a food web is true?
(A) It shows a linear flow of energy from one trophic level to the next.
(B) It shows the complex interconnections between multiple food chains in an ecosystem.
(C) It involves only producers and consumers.
(D) It does not include decomposers.
Answer: (B) It shows the complex interconnections between multiple food chains in an ecosystem.
Explanation:
A food web represents the interconnected food chains within an ecosystem. It shows how different species interact with one another as they transfer energy, including producers, consumers, and decomposers.
Question 49:
Which of the following organisms is a decomposer in an ecosystem?
(A) Grass
(B) Fungi
(C) Rabbit
(D) Eagle
Answer: (B) Fungi
Explanation:
Decomposers, such as fungi and bacteria, break down dead organic material, recycling nutrients back into the ecosystem. Grass, rabbits, and eagles are not decomposers; they play different roles in the food chain.
Question 50:
Which of the following ecosystems is considered the most productive in terms of biomass production?
(A) Grassland
(B) Desert
(C) Coral reefs
(D) Arctic tundra
Answer: (C) Coral reefs
Explanation:
Coral reefs are among the most productive ecosystems on Earth in terms of biomass production due to their high biodiversity, efficient nutrient cycling, and the vast array of species that contribute to primary and secondary productivity.
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