Bihar Board - Class 12 Biology - Chapter 14: Ecosystem Short Answer Question

1. What is the 10 law? 

Ans. At each trophic level 90  of energy is degraded into heat and only 10  is transferred to the next trophic level. This rule is known as the 10  law.

2. What is the shape of the pyramid of biomass in the sea? Why? 

Ans. The shape of the pyramid of biomass in the sea is inverted. This is because the amount of biomass is maximum at the apex of the pyramid and least at the bottom of the pyramid.

3. Give an example of an ecological pyramid that is always upright. Justify your answer. 

Ans. The pyramid of energy is always upright and can never be inverted because some energy is always lost as heat as energy flows from one trophic level to the next.

4. Gaseous nutrient cycles and sedimentary nutrient cycles have their reservoir. Name them. Why is a reservoir necessary? 

Ans. The atmosphere serves as a reservoir for the gaseous nutrient cycle, while the Earth's crust serves as a reservoir for the sedimentary nutrition cycle. The reservoir is required to meet the deficit caused by an imbalance in the influx and efflux. 

5. What are the limitations of ecological pyramids? 

Ans. The following are the limitations of ecological pyramids: 

i. Does not account for the equivalent species belonging to two or more trophic levels.

ii. Assumes a simple food chain and does not account for a food web.

iii. Saprophytes have been excluded from ecological pyramids

6. Name any four ecosystem services. Who gave the price tags on nature’s life support services? Which is the most important ecosystem service provider? 

Ans. Four ecosystem services provided by the natural ecosystem are: - 

i. Drought and flood mitigation.

ii. Offer aesthetic, cultural, and spiritual values.

iii. Cycling nutrients and generating fertile soil.

iv. Providing habitat for wildlife, pollinating flowers, and maintaining Biodiversity.

Robert Constanza have price tags to nature's life support services. Soil formation is the most important ecosystem services provider.

7. Why is secondary succession faster than primary succession? 

Ans. Secondary succession is the development of a community on a site that was previously occupied by well-developed communities where the environment is both organic and inorganic. Secondary succession is faster than primary succession because these bare areas have suitable soil for proper growth.

8. “Energy flow in an ecosystem is always unidirectional”. Justify the statement. 

Ans. Energy flow in an ecosystem is always unidirectional, which means that it is always transferred from one trophic level to the next and is never reverted. Example: - Energy from the sun is captured by producers, which is then consumed by the primary consumer, and energy is transferred to the next trophic level.

9. Explain why the pyramid of energy of an ecosystem is always upright and never inverted?

Ans. The pyramid of energy represents the total amount of energy utilized by the different trophic level organisms in a unit area. The pyramid of energy of the ecosystem is always upright and can never be inverted. This is because when energy flows from one trophic level to the next, some energy is always degraded as heat at each step. 

10. Why is the productivity of coral reefs maximum? 

Ans. The productivity of coral reefs is maximum because of the availability of good light, enough warmth, water, and abundant nutrients.