Chapter 14: Ecosystem

Q1. What is an ecological pyramid? Name three types.

Solution

Pyramid of numbers: Number of organisms at each level
Pyramid of biomass: Total biomass at each level
Pyramid of energy: Energy flow at each level (always upright)

Q2. What is the 10% law of energy transfer?

Solution

Only about 10% of energy is transferred from one trophic level to the next. The rest is lost as heat through respiration.

Q3. What is ecological succession? Name its types.

Solution

Primary succession: On bare/uninhabited land (e.g., lava, sand)
Secondary succession: On previously inhabited but disturbed land (e.g., abandoned farmland)

Q4. What are biogeochemical cycles? Name two types.

Solution

Gaseous: Carbon cycle, Nitrogen cycle (atmosphere as reservoir)
Sedimentary: Phosphorus cycle, Sulphur cycle (rocks/soil as reservoir)

Q5. What is biodiversity? Why is it important?

Solution

Importance: (1) Ecological services (2) Food and medicine (3) Industrial products (4) Aesthetic value (5) Ecosystem stability

Q6. What are the components of an ecosystem?

Solution

Abiotic: Light, temperature, water, soil, minerals
Biotic: Producers, Consumers (herbivores, carnivores), Decomposers

Q7. What is the carbon cycle?

Solution

Pathways: (1) Photosynthesis - CO₂ absorbed by plants (2) Respiration - CO₂ released (3) Decomposition (4) Combustion (5) Ocean absorption

Q8. What is the nitrogen cycle? Describe nitrogen fixation.

Solution

Steps: (1) Biological fixation - Rhizobium, Azotobacter (2) Atmospheric fixation - Lightning (3) Industrial fixation - Haber process (4) Symbiotic fixation (5) Free-living fixation - Clostridium

Q9. What are ecosystem services?

Solution

1. Provisioning: Food, water, timber
2. Regulating: Climate regulation, flood control
3. Cultural: Recreation, aesthetic values
4. Supporting: Soil formation, nutrient cycling

Q10. How does energy flow in an ecosystem?

Solution

Sun → Producers (1% solar) → Primary consumers (10%) → Secondary (10%) → Tertiary (10%)
Energy lost as heat at each level (90% lost through respiration)

Q11. What is primary succession? Describe the stages.

Solution

Stages: (1) Pioneer species (lichens) (2) Soil formation (3) Small plants (4) Shrubs (5) Trees (6) Climax community
Time: Hundreds to thousands of years

Q12. What are the differences between food chain and food web?

Solution

Food chain: Linear sequence, single pathway
Food web: Interconnected chains, multiple pathways, more stable

Q13. What is the phosphorus cycle?

Solution

Called sedimentary because: (1) Main reservoir is rocks/soil (2) No gaseous phase (3) Enters through weathering (4) Absorbed by plants (5) Returns through decomposition

Q14. Which ecological pyramid is always upright?

Solution

Pyramid of numbers: Can be upright or inverted
Pyramid of biomass: Can be inverted (aquatic)
Pyramid of energy: Always upright (10% law)

Q15. What is the significance of studying ecosystem ecology?

Solution

1. Understanding energy flow and nutrient cycling
2. Conservation of biodiversity
3. Managing natural resources sustainably
4. Predicting environmental changes
5. Planning for sustainable development

← Chapter 13: Organisms and Populations Chapter 15: Biodiversity and Conservation →

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