Ecosystem Chapter-Wise Test 23

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the primary function of decomposers in an ecosystem?

Fixing carbon dioxide
Breaking down organic matter into inorganic substances
Providing energy to herbivores
Capturing solar energy
2

Decomposers break down dead organic matter into simpler inorganic nutrients, making them available for uptake by producers.

Which of the following ecosystems has the lowest net primary productivity?

Tropical rainforest
Grassland
Desert
Wetland
3

Deserts have the lowest net primary productivity due to limited water availability and extreme climatic conditions.

Which of the following is NOT an example of a man-made ecosystem?

Crop field
Forest
Aquarium
Garden
2

Forests are natural ecosystems, whereas crop fields, aquariums, and gardens are human-made ecosystems.

Which of the following statements about the nitrogen cycle is incorrect?

Nitrogen fixation converts atmospheric nitrogen into usable forms
Denitrification releases nitrogen gas into the atmosphere
Plants directly absorb atmospheric nitrogen
Decomposers release nitrogen from organic matter into the soil
3

Plants cannot absorb atmospheric nitrogen directly; they rely on nitrogen-fixing bacteria to convert it into a usable form.

Which of the following is an example of a producer in an aquatic ecosystem?

Phytoplankton
Zooplankton
Fish
Crab
1

Phytoplankton are primary producers in aquatic ecosystems, performing photosynthesis to produce energy.

Which of the following statements about detritus food chains is correct?

It starts with living producers
It begins with dead organic matter
It does not involve decomposers
It is independent of the grazing food chain
2

The detritus food chain begins with dead organic matter, which is broken down by decomposers before being passed on to consumers.

Which of the following statements about biogeochemical cycles is incorrect?

They involve both living and non-living components
They help recycle essential elements
Nutrients are lost permanently from the ecosystem
Microorganisms play a role in nutrient cycling
3

Nutrients are not lost permanently; they are continuously recycled in ecosystems.

Which of the following statements about the nitrogen cycle is correct?

Plants directly absorb atmospheric nitrogen
Denitrification converts nitrates into nitrogen gas
Nitrogen fixation releases nitrogen gas into the air
Decomposers are not involved in the nitrogen cycle
2

Denitrification is the process by which nitrates are converted back into nitrogen gas by bacteria, releasing it into the atmosphere.

Why is the detritus food chain important in a terrestrial ecosystem?

It reduces the number of primary consumers
It recycles nutrients into the ecosystem
It produces more energy than the grazing food chain
It increases the biomass of herbivores
2

The detritus food chain plays a vital role in nutrient recycling by decomposing dead organic matter into usable forms.

Which of the following best defines standing crop in an ecosystem?

Total biomass of living organisms in a given area at a given time
Total energy produced by an ecosystem per year
Total number of consumers in an ecosystem
Total amount of decomposed organic matter
1

Standing crop refers to the total biomass of living organisms in a particular trophic level at a given time.

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