What is sexual reproduction? List its four significances.

Any four methods of contraception used by humans. How does their use have a direct effect on the health and prosperity of the family? 

What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?

How do organisms, whether reproduced asexually or sexually maintain a constant chromosome number through several generations? Explain with the help of suitable example.

What is contraception? Name any two methods. How does the use of these methods have a direct effect on the health and prosperity of a family? State any three points.

What is an organic evolution? It cannot be equated with progress. Explain with the help of a suitable example.

What is vegetative propagation? State two advantages and two disadvantages of this method.

1. List in tabular form two differences between binary fission and multiple fission.
2. What happens when a mature Spirogyra filament attains considerable length.

What are sexually transmitted diseases. List two example of each diseases caused due to,

1. Bacterial infection.
2. Viral infection.

Which device or devices may be used to prevent the spread of such diseases.

Describe reproduction by spores in Rhizopus.