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

Is there a relationship between the size of an organism and its life span? Give two examples in support of your answer.

Given below are the events in human reproduction. Write them in correct sequential order.

Insemination, gametogenesis, fertilisation, parturition, gestation, implantation

What is artificial selection? Do you think it affects the process of natural selection? How?

Diseases are broadly grouped into infectious and non-infectious diseases. In the list given below, identify the infectious diseases.

1. Cancer
2. Influenza
3. Allergy
4. Small pox

What is secondary metabolism?

Diseases like dysentery, cholera, typhoid etc., are more common in overcrowded human settlements. Why?

What are three options to increase food production? Discuss each giving the salient features, merits and demerits.

A patient was advised to have a kidney transplant. To suppress the immune reaction, the doctor would administer him ______.

Retroviruses have no DNA. However, the DNA of the infected host cell does possess viral DNA. How is it possible?

Rearrange the following in the correct sequence to accomplish an important biological reaction:

(a) In vitro synthesis of copies of DNA of interest

(b) Chemically synthesized oligonucleotides

(c) Enzyme DNA-polymerase

(d) Complementary region of DNA

(e) Genomic DNA template

(f) Nucleotides provided

(g) Primers

(h) Thermostable DNA-polymerase (from Thermus aquaticus)

(i) Denaturation of ds-DNA

Identify 'a' and 'b' in the figure given below representing proportionate number of major vertebrate taxa.

Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule

Name the type biodiversity represented by the following: 

(a) 50,000 different strains of rice in India.

(b) Estuaries and alpine meadows in India

Describe the asexual and sexual phases of life cycle of Plasmodium that causes malaria in humans

State the role of DNA ligase in biotechnology.

Name of parasite the causes filariasis in humans. Mention its two diagnostic symptoms. How is this transmitted to others?

Explain the work carried out by Cohen and Boyer that contributed immensely in biotechnology.

Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain.

Study a part of the life cycle of malarial parasite given below. Answer the questions that follow:

(a) Mention the roles of ‘A’ in the life cycle of the malarial parasite.

(b) Name the event ‘C’ and the organ where this event occurs.

(c) Identify the organ ‘B’ and name the cells being released from it.

Mention the kind of biodiversity of more than a thousand varieties of mangoes in India represent. How is it possible?