How many chromosomes do drones of honeybee possess? Name the type of cell division involved in the production of sperms by them.

What is a cistron?

Why do moss plants produce very large number of male gametes? Provide one reason. What are these gametes called?

(a) Select the homologous structures from the combinations given below :
(i) Forelimbs of whales and bats
(ii) Tuber of potato and sweet potato
(iii) Eyes of octopus and mammals
(iv) Thorns of Bougainvillea and tendrils of Cucurbita

(b) State the kind of evolution they represent.

(a) Why are the plants raised through micro-propagation termed as somaclones?
(b) Mention two advantages of this technique.

Explain the different steps involved during primary treatment phase of sewage.