Question 21:
Which of the following is not a component of the detritus food chain?
(A) Fungi
(B) Earthworms
(C) Herbivores
(D) Bacteria
Answer: (C) Herbivores
Explanation:
The detritus food chain consists of organisms that feed on dead organic matter (detritus), such as fungi, earthworms, and bacteria. Herbivores, on the other hand, are part of the grazing food chain because they feed directly on living plants (producers).
Question 22:
The relationship between a remora fish and a shark, where the remora benefits by attaching itself to the shark for transportation and food scraps, without harming the shark, is an example of:
(A) Parasitism
(B) Commensalism
(C) Mutualism
(D) Predation
Answer: (B) Commensalism
Explanation:
Commensalism is a type of symbiotic relationship where one organism benefits, and the other is neither harmed nor helped. In this case, the remora fish benefits from the shark by gaining food and transportation, while the shark is unaffected.
Question 23:
Secondary productivity in an ecosystem refers to:
(A) The total biomass produced by primary producers
(B) The biomass produced by herbivores and carnivores
(C) The amount of energy captured from the sun
(D) The rate of organic matter production by decomposers
Answer: (B) The biomass produced by herbivores and carnivores
Explanation:
Secondary productivity refers to the generation of biomass by consumers (herbivores, carnivores) through feeding on primary producers or other consumers. It represents the flow of energy from one trophic level to the next in an ecosystem.
Question 24:
In which of the following biogeochemical cycles is nitrogen fixation a key process?
(A) Water cycle
(B) Carbon cycle
(C) Nitrogen cycle
(D) Phosphorus cycle
Answer: (C) Nitrogen cycle
Explanation:
Nitrogen fixation is a process in which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds, making it available for uptake by plants. It is a key step in the nitrogen cycle.
Question 25:
Which of the following ecosystems has the highest net primary productivity?
(A) Desert
(B) Tropical rainforest
(C) Tundra
(D) Open ocean
Answer: (B) Tropical rainforest
Explanation:
Tropical rainforests have the highest net primary productivity due to their favorable climate, which supports year-round photosynthesis and high biodiversity. Deserts, tundras, and open oceans have comparatively lower primary productivity.
Question 26:
In ecological terms, which of the following is an example of a “carbon sink”?
(A) Animals
(B) Forests
(C) Oceans
(D) Both (B) and (C)
Answer: (D) Both (B) and (C)
Explanation:
A carbon sink is any system that absorbs more carbon than it releases. Forests and oceans are significant carbon sinks, as forests absorb CO₂ through photosynthesis, and oceans dissolve CO₂ and store it in various forms.
Question 27:
During nitrogen fixation, which of the following organisms play a major role?
(A) Cyanobacteria
(B) Fungi
(C) Earthworms
(D) Phytoplankton
Answer: (A) Cyanobacteria
Explanation:
Cyanobacteria, also known as blue-green algae, are a group of microorganisms that can fix atmospheric nitrogen into a form that plants can use. They play a significant role in the nitrogen cycle.
Question 28:
Which of the following is an abiotic component of an ecosystem?
(A) Algae
(B) Bacteria
(C) Soil
(D) Grass
Answer: (C) Soil
Explanation:
Abiotic components of an ecosystem are non-living factors that influence the environment, such as soil, water, temperature, and light. Algae, bacteria, and grass are living (biotic) components.
Question 29:
In the pyramid of biomass, which type of ecosystem typically shows an inverted pyramid?
(A) Grassland ecosystem
(B) Marine ecosystem
(C) Forest ecosystem
(D) Desert ecosystem
Answer: (B) Marine ecosystem
Explanation:
In a marine ecosystem, the pyramid of biomass is often inverted because the biomass of phytoplankton (producers) is very small compared to the biomass of consumers such as fish. Despite their small biomass, phytoplankton reproduce rapidly and support large populations of consumers.
Question 30:
Which of the following is an example of an autotroph?
(A) Fungi
(B) Deer
(C) Algae
(D) Wolf
Answer: (C) Algae
Explanation:
Autotrophs are organisms that produce their own food through processes like photosynthesis. Algae, like plants, are autotrophs because they use sunlight to synthesize their own food. Fungi, deer, and wolves are heterotrophs, relying on other organisms for food.
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