Basics of Ecosystems MCQs

1. What is an ecosystem?

a) Only living organisms in an area b) Interaction between biotic and abiotic components c) A single species population d) Non-living elements like rocks and water

Correct Answer: b) Interaction between biotic and abiotic components

Explanation:
An ecosystem is a dynamic complex of plant, animal, and microorganism communities interacting with their non-living environment (air, water, soil) as a functional unit. This definition emphasizes the interconnectedness of living and non-living components.

2. The functional unit of an ecosystem includes:

a) Only plants and animals b) Energy flow and nutrient cycling c) Only climatic conditions d) Human activities

Correct Answer: b) Energy flow and nutrient cycling

Explanation:
The two fundamental functional processes that characterize ecosystems are: (1) Energy flow through food chains (unidirectional), and (2) Biogeochemical cycling of nutrients (cyclic). These processes maintain the ecosystem's structure and function.

3. Which is an abiotic component of an ecosystem?

a) Trees b) Bacteria c) Sunlight d) Birds

Correct Answer: c) Sunlight

Explanation:
Abiotic components are non-living physical and chemical factors like sunlight, temperature, water, minerals, and gases. These provide the energy and materials needed by biotic components (living organisms) to survive and reproduce.

4. The term "ecosystem" was first introduced by:

a) Charles Darwin b) Rachel Carson c) Sir Arthur Tansley d) Alexander von Humboldt

Correct Answer: c) Sir Arthur Tansley

Explanation:
British ecologist Arthur Tansley coined the term "ecosystem" in 1935 to describe the complex interactions between organisms and their environment. His concept integrated earlier ideas about communities and their physical surroundings.

5. The word "ecology" was coined by:

a) Charles Darwin b) Earnest Haeckel c) Gregor Mendel d) Carl Linnaeus

Correct Answer: b) Earnest Haeckel

Explanation:
German biologist Ernst Haeckel introduced the term "ecology" (from Greek "oikos" meaning house/habitat) in 1866 to describe the study of organisms' relationships with each other and their environment. He defined it as "the comprehensive science of the relationship of the organism to the environment."

6. The smallest unit of the biosphere is:

a) Ecosystem b) Community c) Population d) Organism

Correct Answer: a) Ecosystem

Explanation:
The hierarchy of ecological organization progresses from individual organisms → populations → communities → ecosystems → biosphere. An ecosystem is the smallest unit that contains both biotic and abiotic components and can function independently within the biosphere.

7. Ecology studies:

a) Environment only b) Living components only c) Non-living components only d) All the above (environment, living/non-living components, organisms)

Correct Answer: d) All the above (environment, living/non-living components, organisms)

Explanation:
Ecology is the interdisciplinary scientific study of: (1) Organisms' relationships with each other (biotic factors), (2) Their physical environment (abiotic factors), and (3) The flows of energy and matter through these systems. It integrates biology, chemistry, physics, and earth sciences.

8. The region of Earth where life exists is called:

a) Atmosphere b) Biosphere c) Hydrosphere d) Lithosphere

Correct Answer: b) Biosphere

Explanation:
The biosphere extends from about 8 km above Earth's surface to 11 km below ocean surfaces, encompassing all living organisms and their environments. It includes parts of the atmosphere (air), hydrosphere (water), and lithosphere (land) where life exists.

9. In the biosphere, energy is primarily received from:

a) The Sun b) Geothermal sources c) Chemical reactions d) Tidal forces

Correct Answer: a) The Sun

Explanation:
Solar radiation provides 99.9% of Earth's surface energy. Plants capture ~1-2% of incident sunlight via photosynthesis, which then flows through food chains. Other sources contribute minimally (geothermal: 0.013%, tidal: 0.002% of Earth's energy budget).

10. Organic components of an ecosystem include:

a) Carbohydrates b) Proteins c) Fats d) All the above

Correct Answer: d) All the above

Explanation:
Organic compounds in ecosystems contain carbon and are produced by living organisms. These include: (1) Carbohydrates (sugars, cellulose), (2) Proteins (enzymes, structural components), (3) Lipids (fats, oils), and (4) Nucleic acids (DNA, RNA). They form the biochemical basis of life.

1. Ecosystem Fundamentals

Your Score: /10