Ecosystem: MCQ Test

1. Which of the following best describes an ecosystem as a functional unit of nature?

• A collection of different species living in the same geographical area.
• Living organisms interacting exclusively among themselves.
• Living organisms interacting among themselves and also with the surrounding physical environment.
• Only the physical environment affecting living organisms.

2. Which of the following are examples of man-made ecosystems?

• Forest and grassland
• Pond and lake
• Crop fields and an aquarium
• River and estuary

3. The entire biosphere is often regarded as a global ecosystem. For convenience in study, this vast system is divided into which two basic categories?

• Tropical and polar
• Terrestrial and aquatic
• Mountain and plain
• Desert and forest

4. Which of the following aspects are considered when the components of an ecosystem are seen to function as a unit?

• Solar input and temperature cycles
• Species composition and stratification
• Productivity, decomposition, energy flow, and nutrient cycling
• Biotic and abiotic factors

5. The vertical distribution of different species occupying different levels in an ecosystem, such as trees, shrubs, and herbs in a forest, is called:

• Species composition
• Biodiversity
• Stratification
• Ecological succession

6. In a pond ecosystem, which group represents the autotrophic components?

• Zooplankton and free swimming forms
• Fungi, bacteria, and flagellates
• Phytoplankton, some algae, and floating plants
• Fish and insects

7. Where are decomposers (fungi, bacteria, and flagellates) especially abundant in a pond ecosystem?

• Near the surface
• In the middle water column
• At the edges where plants grow
• In the rich soil deposit at the bottom

8. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of:

• gm⁻² only
• kcal m⁻² only
• gm⁻² or kcal m⁻²
• gm⁻² yr⁻¹ or kcal m⁻² yr⁻¹

9. The rate of biomass production is called productivity. To compare the productivity of different ecosystems, it is expressed in terms of:

• gm⁻² only
• kcal m⁻² only
• gm⁻² or kcal m⁻²
• gm⁻² yr⁻¹ or (kcal m⁻²) yr⁻¹

10. Which of the following equations accurately represents Net Primary Productivity (NPP)?

• NPP = GPP + R
• NPP = R - GPP
• NPP = GPP - R
• NPP = GPP / R

11. Net primary productivity (NPP) is the available biomass for consumption by:

• Producers
• Autotrophs
• Heterotrophs (herbivores and decomposers)
• Only primary carnivores

12. Secondary productivity is defined as the rate of formation of new organic matter by which group of organisms?

• Producers
• Consumers
• Decomposers
• Photosynthetic bacteria

13. The annual net primary productivity of the entire biosphere is approximately 170 billion tons (dry weight) of organic matter. What percentage of this comes from the oceans?

• Approximately 70%
• Approximately 32%
• Approximately 50%
• Approximately 10%

14. Decomposition involves the breakdown of complex organic matter into inorganic substances. Which of the following is the raw material for this process?

• Living organisms
• Humus
• Detritus
• Water-soluble nutrients

15. Which step in the decomposition process involves detritivores (e.g., earthworms) breaking down detritus into smaller particles?

• Leaching
• Catabolism
• Fragmentation
• Mineralisation

16. What is the process called when water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts?

• Catabolism
• Humification
• Leaching
• Mineralisation

17. Humification leads to the accumulation of humus, which is characterized as a dark-coloured amorphous substance that is:

• Easily degraded by microbial action
• Highly resistant to microbial action
• A crystalline substance that releases nutrients rapidly
• Non-colloidal in nature

18. The process by which microbes further degrade humus and release inorganic nutrients is known as:

• Fragmentation
• Leaching
• Catabolism
• Mineralisation

19. Which of the following conditions would generally inhibit the rate of decomposition?

• Warm temperature and moist environment
• High nitrogen and sugar content in detritus
• Low temperature and anaerobiosis
• Presence of abundant earthworms

20. Decomposition rate is slower if detritus is rich in which chemical compositions?

• Nitrogen and water-soluble sugars
• Lignin and chitin
• Proteins and carbohydrates
• Fats and lipids