Reproduction in organisms — BIOLOGY STD 12 Science — Question

How does prey species defend themselves against predators?

Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens? What type of immunity do you observe in this case?

A population of Paramoecium caudatum was grown in a culture medium. After 5 days the culture medium became overcrowed with Paramoeium and had depleted nutrients. What will happen to the population and what type of growth curve will the population attain? Draw the growth curve.

Sketch and label the T. S. of the thyroid gland.

Food chain and Food web.

Pihu told her sister Pari that even after five years of marriage she is not able to bear a child and have to hear sarcastic remarks of her in-laws that make her depressed. Pari told Pihu that she and her husband should get examined by a doctor. After examination, doctor found no abnormalities in Pihu and her husband except low sperm count and some defects in the erection of penis of her husband.

1. What are the possible causes of low sperm counts?
2. What is the use of erection of penis?
3. What are the possible treatments?
4. Mention the values shown by Pari.

What accounts for the greater ecological diversity of India?

What is an operon? Name any four operons in E.coli.

Three microbes are listed below. Name the product produced by each one of them and mention their use:

1. Aspergillus niger.
2. Trichoderma polysporum.
3. Monascus purpureus.

Draw a diagram showing steps in r-DNA technology.