Science (English Medium) कक्षा १२ - CBSE Important Questions

Many copepods live on the body surface of marine fish. This relationship is an example of ______.

"Some species of insects and frogs have evolved with various specific features that help them from being detected."

1. Justify the statement giving reasons.
2. Mention any two such features.

Observe the graph given below.

a) Which species is competitively superior? Support it with the data provided in the graph.

b) State the underlying principle for the above result and name the scientist associated with this principle.

c) Explain the mechanism in which two or more species competing with each other can co-exist.

OR

Graphs A and B shown below depict interaction of two species. Which graph indicates Mutualism? Give reason.

A	B

Write the equation that helps in deriving the net primary productivity of an ecosystem.

Why the pyramid of energy is always upright? Explain.

“The pyramid of biomass is not always upright.” Explain the statement.

What is the primary productivity of an ecosystem and how is it expressed?

Explain what does the equation given below show :
NPP = GPP – R

Name the type of detritus that decomposes faster. List any two factors that enhance the rate of decomposition.

Write the different steps taken in humification and mineralisation during the process of decomposition.

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

Answer the following question.
What is an ecological pyramid? Compare the pyramids of energy, biomass, and numbers.

Answer the following question.
Write any two limitations of ecological pyramids.

Write the relationship between productivity, gross primary productivity, net primary productivity, and secondary productivity.

'The pyramid of energy is always upright.' Explain

Explain with the help of labelled diagrams, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.

(a) Given below is a pyramid of biomass in an ecosystem where each bar represents the standing crop available in the trophic level. With the help of an example explain the conditions where this kind of pyramid is possible in nature.

(b) Will the pyramid of energy be also of the same shape in this situation? Give a reason for your response.

(a) Draw a pyramid of numbers where a large number of insects are feeding on the leaves of a tree. What is the shape of this pyramid?

(b) Will the pyramid of energy be also of the same shape in this situation? Give a reason for your response.

Observe the contents 1, 2, 3 and 4 of soil samples A, B and C shown in the graph. If the temperature and soil moisture of all soil samples are identical, which soil sample (s) will show faster decomposition?

1 indicates lignin content, 2 indicates chitin, 3 indicates nitrogen content, and 4 indicates sugar content

The biomass of a standing crop of phytoplankton is 4 kg/m², which supports a large standing crop of zooplankton having a biomass of 11 kg/m². This is consumed by small fishes having a biomass of 25 kg/m², which are then consumed by large fishes with a biomass of 37 kg/m².

Draw an ecological pyramid indicating the biomass at each stage and also name the trophic levels. Mention whether it is an upright or inverted pyramid.