Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Mention the various seral stages of xero sere.

What do you mean by foetal ejection reflex?

How has the study of biotechnology helped in developing pest resistant cotton crop? Explain.

Or

One of the major contribution of biotechnology is to develop pest resistant varieties of cotton plants. Explain how it has been made possible.

What is artificial hybridisation? How it can be achieved?

Identify 'a', 'b', 'c', 'd', 'e' and 'f' in the table given below:

No.	Syndrome	Cause	Characteristics of affected individual	Sex Male/Female/Both
1	Down’s	Trisomy of 21	‘a’ (i) (ii)	'b'
2	‘c’	XXY	Overall masculine development	‘d’
3	Turner’s	45 with OX	‘e’ (i) (ii)	‘f’

Given below is a list of autotrophs and heterotrophs. With your knowledge about food chain, establish various linkages between the organisms on the principle of ‘eating and being eaten’. What is this inter-linkage established known as?
Algae, hydrilla, grasshopper, rat, squirrel, crow, maize plant, deer, rabbit, lizard, wolf, snake, peacock, phytoplankton, crustaceans, whale, tiger, lion, sparrow, duck, crane, cockroach, spider, toad, fish, leopard, elephant, goat, Nymphaea, Spirogyra.

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

Expand 'BAC' and 'YAC'. Explain how they were used in sequencing of human genomes.

State what is apomixis. Comment on its significance. How can it be commercially used?

In the figure given below label the following parts: male gametes, egg cell, polar nuclei, synergid and pollen tube,