Evolution — BIOLOGY STD 12 Science — Question

An organic farmer relies on natural predation for controlling plant pests and diseases. Justify giving reasons why this is considered to be a holistic approach.

A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.

1. Why in your opinion the female partner is often blamed for such situations in India? Mention any two values that you as a biology student can promote to check this social evil.
2. State any two reasons responsible for the cause of infertility.
3. Suggest a technique that can help the couple to have a child where the problem is with the male partner.

Differentiate between vaccination and immunisation. Describe the two types of vaccines with suitable examples?

What are the various routes by which transmission of human immunodeficiency virus takes place?

Define and design a test-cross###Explain the test cross by example.

In pea plants, the colour of the flower is either violet or white, whereas human skin colour shows many gradations. Explain giving reasons, how it is possible.

Enumerate the complications that untreated STDs can lead to.

What is artificial hybridisation? How is it useful in plant breeding?

Define the following :
(i) Immunity (ii) Antigen (iii) Antibody (iv) Toxide (v) Immune system.