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

Discuss briefly about Ultraviolet B.

Name the pollutant attributed to be the cause of ‘ozone-hole’ over the Antarctica region.

Answer the following question.
Name the layer of the atmosphere that is associated with ‘good ozone’.

Answer the following question.
Name the layer of the atmosphere that is associated with 'good ozone'.

Justify the need for the signing of the 'Montreal Protocol' by the participating nations in 1987.

Choose the incorrect statement:

What do you understand by Snow-blindness?

It is generally observed that the children who had suffered from chickenpox in their childhood may not contract the same disease in their adulthood. Explain, giving reasons, the basics of such immunity in an individual. Name this kind of immunity.

A heavily bleeding and bruised road accident victim was brought to a nursing home. The doctor immediately gave him an injection to protect him against a deadly disease.

1. Write what did the doctor inject into the patient’s body.
2. How do you think this injection would protect the patient against the disease?
3. Name the disease against which this injection was given and the kind of immunity it provides.

State the cause of adenosine deaminase enzyme deficiency.

Name any two types of cells that act as ‘cellular barriers’ to provide innate immunity in humans.

When and where do chorionic villi appear in humans?

How have human activities caused desertification? Explain.

Highlight the role of thymus as a lymphoid organ.

Comment on the role of placenta as an endocrine gland.

During the reproductive cycle of a human female, when, where and how does a placenta develop? What is the function of placenta during pregnancy and embryo development?

Why is secondary immune response more intense than the primary immune response in humans?

Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.

Differentiate the following and give examples of Active and passive immunity

Suggest a method to ensure an anamnestic response in humans.