Human Health and Disease — BIOLOGY STD 12 Science — Question

Explain the process of secondary treatment given to the primary effluent up to the point it shows significant change in the level of biological oxygen demand (BOD) in it.

Can a disease be detected before its symptoms appear? Explain the principle involved.

How many sperms and ova will be produced by 25 primary spermatocyte and 25 primary oocyte. Give reason also.

Name the blank spaces a, b, c and d in the table given below:

S. No.	Name of the drug	Plant source	Organ system affected
(i)	a	Poppy plant	b
(ii)	Marijuana	c	d

How pollen grains are used, except in fertilisation?

Define seed dormancy. Give the causes and significance of seed dormancy.

A mother of one-year-old daughter wanted to space her second child. Her doctor suggested CuT. Explain its contraceptive actions.

Draw a labelled diagram of:

1. An apocarpous pistil and.
2. A syncarpous pistil. Name an example for each.

Certain attributes of innate immunity are given in the table below. Identify A, B, C, D, E and Frespectively in it.

S.No.	Type of barrier	Example of the barrier	Function
(і)	А	B	Prevent microbial growth
(ii)	C	Polymorpho nuclear leucocytes	D
(iii)	Cytokine	E	F

What will happen to an ecosystem if:
All top carnivore population is removed.