Question

(a) What is menstruation? Why does menstruation occur?
(b) Write the various steps involved in the sexual reproduction in animals.
​(c) Write the differences between aerobic respiration and anaerobic respiration in tabular form. Name one organism which uses aerobic and another which uses anaerobic mode of respiration.

Answer 1

(a) Menstruation is the regular discharge of blood and mucosal tissue from the uterus through the vagina. It is a method to remove the unfertilized eggs from the body at regular intervals.

(b) The events observed during sexual reproduction in animals are -

(i) Formation of gametes
(ii) Fusion of male and female gametes to produce zygote
(iii) Development of zygote and embryogenesis
(iv) Development of an embryo

(c)

Aerobic Respiration	Anaerobic respiration
It involves the complete breakdown of glucose into CO2 and H2O.	It involves the partial breakdown of glucose.
A net gain of 36 molecules of ATP occurs.	A net gain of only 2 molecules of ATP occurs.
Here, oxidation of NADH to NAD+ is a vigorous reaction.	Here, oxidation of NADH to NAD+ is a slow reaction.

Organism which use aerobic respiration - humans
Organism which use anaerobic respiration - yeast