Ecosystem

Previous Years' CBSE Board Questions

12.1 Ecosystem - Structure and Function

VSA (1 mark)

How is 'stratification' represented in a forest ecosystem? (Delhi 2014) R

LA (5 marks)

2 (a) Taking an example of a small pond, explain how the four components of an ecosystem function as a unit.

1. Name the type of food chain that exists in a pond. (Al 2016) (Cr

(2023) U

12.2 Productivity

MCO

1. The primary productivity in an ecosystem is expressed as
2. gm^-2yr^-1 (b) gm^-2yr
3. K cal m-2 yr-1 (d) K cal m^-2. (2023) R

VSA (1 mark)

What does 'R' represent in the given equation for productivity in an ecosystem? <math>GPP - R = NPP</math>. (Delhi 2014 C)

(2019)

SAI (2 marks)

1. Write the relationship between productivity, gross primary productivity, net primary productivity and secondary productivity. (Al 2019)

OR How are productivity, gross productivity, net primary productivity and secondary productivity interrelated? (Delhi 2015)

SAII (3 marks)

1. How would you differentiate between gross primary productivity from net primary productivity and

secondary productivity of an ecosystem. (2020)

OR IX

Describe the inter-relationship between productivity, gross primary productivity and net productivity.

(AI 2017) VII

1. (a) What is the primary productivity of an ecosystem and how is it expressed?

1. Explain what does the equation given below show: NPP = GPP - R (2019)
2. (a) What is primary productivity? Why does it vary in different types of ecosystems?

IV

1. State the relation between gross and net primary productivity. (Delhi 2014)

12.3 Decomposition

MCQ

1. Assertion (A): Decomposition process is slower if detritus is rich in lignin and cutin. Reason (R): Decomposition is largely an oxygen- requiring process.
2. Both (A) and (R) are true and (R) is the correct explanation of (A).
3. Both (A) and (R) true, but (R) is not the correct explanation of (A).
4. (A) is true, but (R) is false.
5. (A) is false, but (R) is true.

SAI (2 marks)

10. How is humus formed? Mention any three

characteristics of humus. (2020)

SA II (3 marks)

1. (a) Name the type of detritus that decomposes faster. List any two factors that enhance the rate of decomposition.
2. Write the different steps taken in humification and mineralisation during the process of decomposition.
3. Why is earthworm considered a farmer's friend? Explain humification and mineralisation occurring in a decomposition cycle. (Foreign 2015)
4. How does a detritivore differ from a decomposer? Explain with an example each. (Delhi 2015C) R

12.4 Energy Flow

MCQ

14. In the illustration given below of a simplified food

web on an island, the arrows indicate the direction

of energy flow and the Roman numbers indicate

species within the food web.

At which trophic level or levels does the species VIII function?

1. 2^nd and 3^rd consumer (b) 1^st consumer
2. Producer (d) 3rd and 4th consumer

(2020)

VSA (1 mark)

1. "Man can be a primary as well as a secondary consumer." Justify this statement. (Foreign 2015)

SA II (3 marks)

1. Justify the importance of decomposers in an ecosystem. (Foreign 2015)

12.5 Ecological Pyramids

MCQ

1. Given below is a diagram of an ecological pyramid of numbers. Choose the correct food chain from the list of food chain given, that represent the given pyramid.

1. <math>Grass \rightarrow Goat \rightarrow Fox \rightarrow Tiger</math>
2. Mice → Cat → Hyena → Cheetah
3. <math>Grass \rightarrow Rabbit \rightarrow Fox \rightarrow Flea</math>
4. Grass → Insects → Sparrow → Snake (2023) Ap

SAI (2 marks)

Given below is a food web that involves nine organisms.

1. Identify two producers and two carnivores shown in the food web.
2. Is it possible to make an ecological pyramid depicting this food web? Give reason in support of your answer. (2023) [An]

Name the type of ecological pyramid that can exist as upright as well as inverted. Explain how does it happen. (2020)

1. (a) How many primary producers do you think will be needed to support six tertiary consumers in a grassland ecosystem?
2. Draw a grassland pyramid to substantiate your answer. (2020)

SA II (3 marks)

1. (a) Name an ideal pyramid existing in an ecosystem. Construct it upto its three trophic levels along with their names.
2. The sun provides 1,000,000 J of sunlight (solar energy) to an ecosystem. Write the amount of energy that is available to the first and third trophic levels.

(2020) (AD

Explain giving reasons that pyramid of energy is

always upright. (2019 C)

"In a food chain, a trophic level represents a

functional level, not a species". Explain.

(Delhi 2016) 🕕

LA (5 marks)

1. (a) Construct a pyramid of biomass of grassland ecosystem. How is the pyramid of biomass in sea different from it?
2. Name the primary producer and primary consumer in sea.
3. What is standing crop? (2020 C)
4. (a) 'The pyramid of energy is always upright'. Explain.
5. Explain with the help of labelled diagrams, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.

(Al 2019)

1. (a) What does an ecological pyramid represent? State any two limitations that these pyramids have.
2. Describe an inverted pyramid of biomass with the help of an example. (2019)
3. (a) What is a trophic level in an ecosystem? What is 'standing crop' with reference to it?
4. Explain the role of the 'first trophic level' in an ecosystem.
5. How is the detritus food chain connected with the grazing food chain in a natural ecosystem? (2018)
6. (a) What is an ecological pyramid? Compare the pyramids of energy, biomass and numbers.
7. Write any two limitations of ecological pyramids. (NCERT Exemplar, Al 2017) III

"It is often said that the pyramid of energy is always

upright. On the other hand, the pyramid of biomass

can be both upright and inverted." Explain with the

help of examples and sketches. (AI 2015)

1. (a) With suitable examples, explain the energy flow through different trophic levels. What does each bar in this pyramid represent?
2. Write any two limitations of ecological pyramids. (AI 2014C)