Principles of Inheritance and Variations — BIOLOGY STD 12 Science — Question

Make a labelled diagram of an RNA dinucleotide showing its 3' → 5' polarity.

Explain why using tobacco in any form is injurious to health.

Name the group of cells the HIV enters after getting into the human body. What happens in these cells and what are these cells subsequently referred to as? Name the next group of cells the HIV attacks from here.

Briefly mention the contribution of T.H. Morgan in genetics.

"Crystals of Bt. toxic protein synthesized by some bacteria, kill the insect but not kill them-selves." Explain the statement with reason.

Since the origin of life on earth, there were five episodes of mass extinction of species.

1. How is the 'Sixth Extinction', presently in progress, different from the previous episodes?
2. Who is mainly responsible for the 'Sixth Extinction?
3. List any four points that can help to overcome this disaster.

Why are nutrient cycles in nature called biogeochemical cyles?

What is biotechnology? Describe its two applications in the field of Agriculture.

How do mycorrhizae act as biofertilisers? Explain. Name a genus of fungi that forms a mycorrhizal association with plants

State the role of T lymphocytes and B lymphocytes in developing acquired immunity against certain diseases.

OR

Name the different types of cells that are responsible for producing the acquired immune response in a human body. How do these cells respond when a pathogen enters the body?

OR

 Name the two special types of lymphocytes in humans. How do they differ in their roles in immune response?