Science (English Medium) Class 12 - CBSE Question Bank Solutions for Biology

Draw a diagrammatic sketch of biogas plant, and label its various components given below: Gas Holder, Sludge Chamber, Digester, Dung+water chamber.

The process of mineralisation by micro organisms helps in the release of ______.

What is common to earthworm, mushroom, soil mites and dung beetle in an ecosystem?

What could be the reason for the faster rate of decomposition in the tropics?

How do you distinguish between humification and mineralisation?

The rate of decomposition of detritus is affected by the abiotic factors like availability of oxygen, pH of the soil substratum, temperature etc. Discuss.

A farmer harvests his crop and expresses his harvest in three different ways.

1. I have harvested 10 quintals of wheat.
2. I have harvested 10 quintals of wheat today in one acre of land.
3. I have harvested 10 quintals of wheat in one acre of land, 6 months after sowing.

Do the above statements mean one and the same thing. If your answer is yes, give reasons. And if your answer is ‘no’ explain the meaning of each expression.

Match the animals given in column I with their location in column II:

Choose the correct match from the following:

What is common to the following plants: Nepenthes, Psilotum, Rauwolfia and Aconitum?

What could have triggered mass extinctions of species in the past?

What does 'Red' indicate in the IUCN Red list (2004)?

Explain as to how protection of biodiversity hot spots alone can reduce up to 30% of the current rate of species extinction.

What is common to the species shown in figures A and B?

A	B

What is common to the species shown in figures A and B?

A	B

Of the four major causes for the loss of biodiversity (Alien species invasion, habitat loss and fragmentation, over-exploitation and co-extinctions which according to you is the major cause for the loss of biodiversity? Give reasons in support.

Discuss one example, based on your day-to-day observations, showing how loss of one species may lead to the extinction of another.

What criteria should one use in categorizing a species as threatened?

List any two major causes other than anthropogenic causes of the loss of biodiversity.

Explain the concept of "co-extinction" by taking two examples.

How can you, as an individual, prevent the loss of biodiversity?