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

What characteristics make a community stable?

According to David Tilman, greater the diversity, greater is the primary productivity. Can you think of a very low diversity man-made ecosystem that has high productivity?

Elaborate how invasion by an alien species reduces the species diversity of an area.

Can you think of a scientific explanation, besides analogy used by Paul Ehrlich, for the direct relationship between diversity and stability of an ecosystem?

Explain briefly the ‘rivet popper hypothesis’ of Paul Ehrlich.

The figure below shows the structure of a plasmid.

A foreign DNA was ligated at BamH1. The transformants were then grown in a medium containing antibiotics tetracycline and ampicillin.

Choose the correct observation for the growth of bacterial colonies from the given table.

Study the given diagram of the Sewage Treatment  Plant (S.T.P.) and answer the question that follows:

1. Which one of the two 'S.T.P.' (A) or (B) will be more effective in treating the human excreta in municipal waste?
2. Write the steps followed in carrying the treatment of the sewage in step (Z), once the BOD of sewage is reduced significantly till it is passed on to the "anaerobic sludge digesters".

The primary productivity in an ecosystem is expressed as ______.

1. gm^-2 yr^-1
2. gm^-2 yr
3. Kcal m^-2 yr^-1
4. Kcal m^-2

The wall layer of microsporangium, which nourishes the pollen grain, is ______.

Use the information provided in the table given below to answer the following questions:

1. Calculate the gross primary productivity.
2. Analyze the trend in the Net Production from Producers to Top Carnivore. Give a reason for your observation.

The aeration tank of a sewage treatment plant is not functioning properly. Explain in detail the impact of this on the treatment of sewage and BOD of the effluent.

What is biopiracy?

Why must a cell be made ‘competent’ in biotechnology experiments? How does calcium ion help in doing so?

What are methanogens?

Explain co-evolution with reference to parasites and their hosts.

Mention the type of host cells suitable for the gene guns to introduce an alien DNA.

How did Darwin explain adaptive radiation ? Give another example exhibiting adaptive radiation.

Explain adaptive radiation with the help of a suitable example.

Why are analogous structures a result of convergent evolution?

Cite an example where more than one adaptive radiations have occurred in an isolated geographical area. Name the type of evolution your example depicts and state why it is so named.