Science (English Medium) कक्षा १२ - CBSE Important Questions for Biology

Write two differences between Homo erectus and Homo habilis

Answer the following question.
Write the characteristics of Ramapithecus, Dryopithecus, and Neanderthal man.

According to the Hardy-Weinberg principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population?

How does the Hardy-Wienberg equation explain genetic equilibrium?

At a particular locus, the frequency of allele A is 0.8, and that of allele a is 0.2. What would be the frequency of heterozygotes in a random mating population at equilibrium?

The graphs below show three types of natural selection. The shaded areas marked with arrows show the individuals in the population who are not selected. The dotted vertical lines show the statistical means.

character Graph A	character Graph B	character Graph C

1. What names are given to the types of selection shown in graphs A, B and C?
2. After the selection has operated for several generations in the above populations indicated as, Graph A, B and C, graphically illustrate the probable results.

Explain the various types of cancer

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.

State the cause of adenosine deaminase enzyme deficiency.

How does smoking tobacco in human lead to oxygen deficiency in their body?

Highlight the role of thymus as a lymphoid organ.

The following is well-known abbreviation, which have been used in this chapter. Expand to its full form:

MALT

A group of youth were having a ‘rave party’ in an isolated area and was raided by police. Packets of ‘smack’ and syringes with needles were found littered around.

1. Why is taking ‘smack’ considered an abuse?
2. Write the chemical name of ‘smack’ and the name of its source plant.
3. Syringes and needles used by the youth for taking the drug could prove to be very fatal. Why?

What are interferons?

Mention role of interferons

Name the cells that are released from the above-mentioned gland. Mention how they help in immunity.

You have attended a birthday party hosted by one of your classmates. You found some guests at the party sitting in a corner making a lot of noise and consuming 'something'. After a while one of the boys from the group started screaming, behaving abnormally and sweating profusely. On enquiry you found that the group members were taking drugs.

(a) Would you inform your parents/school authorities ? Yes/No. Give reasons in support of your answer.

(b) Prepare a note to be circulated amongst the schoolmates about the sources and dangers of any two drugs.

(c) Write any two ways that you will suggest to your school principal so as to promote awareness amongst the youth against the use of these drugs.

Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.

(a) What is a vaccine? Explain how does it impart immunity to the child against the disease.
(b) With the help of an example each, differentiate between active and passive immunity.

Explain the relationship between B-lymphocytes and T-lymphocytes developing an immune response.

Where in the human body are its specific receptors located ? How do opioids affect the human body ?