Question 71:
What is the primary role of detritivores in an ecosystem?
(A) They decompose dead organisms
(B) They fix nitrogen in the soil
(C) They convert sunlight into chemical energy
(D) They recycle nutrients by breaking down dead organic matter
Answer: (D) They recycle nutrients by breaking down dead organic matter
Explanation:
Detritivores, such as earthworms and fungi, break down dead organic material and recycle nutrients back into the ecosystem. This process is vital for maintaining nutrient cycles in ecosystems.
Question 72:
Which of the following factors directly affects the rate of primary productivity in an ecosystem?
(A) Number of herbivores
(B) Solar energy input
(C) Availability of carnivores
(D) Population density
Answer: (B) Solar energy input
Explanation:
Primary productivity is directly influenced by the amount of solar energy available to plants for photosynthesis, along with other factors like nutrient availability and water. Herbivores, carnivores, and population density have an indirect effect on primary productivity.
Question 73:
Which of the following is an example of a carbon sink?
(A) Combustion of fossil fuels
(B) Burning of forests
(C) Oceans absorbing atmospheric CO₂
(D) Volcanic eruptions
Answer: (C) Oceans absorbing atmospheric CO₂
Explanation:
Carbon sinks are natural systems that absorb and store carbon from the atmosphere. Oceans are major carbon sinks, as they absorb large amounts of atmospheric CO₂. Forests and soils also act as carbon sinks by storing carbon in plant biomass and organic matter.
Question 74:
In an ecosystem, which of the following is a producer?
(A) Algae
(B) Deer
(C) Eagle
(D) Snake
Answer: (A) Algae
Explanation:
Producers are organisms that produce their own food through photosynthesis. Algae, along with plants, are primary producers in ecosystems. Deer, eagles, and snakes are consumers.
Question 75:
Which of the following ecosystems has the highest biodiversity?
(A) Desert
(B) Tropical rainforest
(C) Arctic tundra
(D) Freshwater lake
Answer: (B) Tropical rainforest
Explanation:
Tropical rainforests have the highest biodiversity of any terrestrial ecosystem due to their warm, stable climate, high levels of rainfall, and abundant energy and nutrient availability. Deserts and tundras have lower biodiversity due to harsher environmental conditions.
Question 76:
Which of the following processes releases carbon dioxide into the atmosphere?
(A) Photosynthesis
(B) Respiration
(C) Nitrogen fixation
(D) Transpiration
Answer: (B) Respiration
Explanation:
Respiration, carried out by both plants and animals, releases carbon dioxide (CO₂) into the atmosphere as a byproduct of breaking down glucose for energy. Photosynthesis absorbs CO₂, while nitrogen fixation and transpiration do not involve CO₂ release.
Question 77:
What is the role of mycorrhizae in ecosystems?
(A) Nitrogen fixation
(B) Helping plants absorb water and nutrients
(C) Decomposing dead organic matter
(D) Transpiration
Answer: (B) Helping plants absorb water and nutrients
Explanation:
Mycorrhizae are symbiotic associations between fungi and plant roots. They enhance the plant’s ability to absorb water and essential nutrients, such as phosphorus, from the soil, thus benefiting plant growth and productivity.
Question 78:
Which of the following ecosystems is considered a “carbon sink”?
(A) Coral reefs
(B) Urban areas
(C) Forests
(D) Agricultural fields
Answer: (C) Forests
Explanation:
Forests act as carbon sinks because trees absorb CO₂ during photosynthesis and store carbon in their biomass. Urban areas and agricultural fields generally do not serve as significant carbon sinks.
Question 79:
Which of the following human activities is the leading cause of deforestation?
(A) Reforestation programs
(B) Industrialization
(C) Slash-and-burn agriculture
(D) Wildlife conservation
Answer: (C) Slash-and-burn agriculture
Explanation:
Slash-and-burn agriculture is one of the major causes of deforestation, especially in tropical regions. This practice involves clearing forests to create farmland, leading to habitat destruction, loss of biodiversity, and disruption of carbon and water cycles.
Question 80:
Which of the following is an example of a density-independent factor affecting population growth?
(A) Competition for food
(B) Predation
(C) Drought
(D) Parasitism
Answer: (C) Drought
Explanation:
Density-independent factors, like drought, affect population size regardless of the population’s density. In contrast, density-dependent factors (such as competition, predation, and parasitism) have a greater impact as population density increases.
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