Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Biology

A plasmid without a selectable marker was chosen as vector for cloning a gene. How does this affect the experiment?

Describe the role of CaCl₂ in the preparation of competent cells?

Name the regions marked A, B and C.

For selection of recombinants, insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.

Describe the role of Agrobacterium tumefaciens in transforming a plant cell.

With respect to understanding diseases, discuss the importance of transgenic animal models.

Name the first transgenic cow. Which gene was introduced in this cow?

Transgenic animals are the animals in which a foreign gene is expressed. Such animals can be used to study the fundamental biological process, phenomenon as well as for producing products useful for mankind. Give one example for each type.

Define transgenic animals. Explain in detail any four areas where they can be utilised.

Productivity is the rate of production of biomass expressed in terms of ______.

Which of the following ecosystems is most productive in terms of net primary production?

Justify the pitcher plant as a producer.

Why are oceans least productive?

Why is the rate of assimilation of energy at the herbivore level called secondary productivity?

Primary productivity varies from ecosystem to ecosystem. Explain?

Justify the following statement in terms of ecosystem dynamics. “Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity”.

Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer. A young forest, a natural old forest, a shallow polluted lake, alpine meadow.

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.