Q9 of 40 Page 1

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

The physical removal of particles from sewage by sedimentation and filtration is known as primary treatment phase of sewage.

Different steps involved –

• Removal of floating debris by sequential filtration.

• Soil and small pebbles are removed by sedimentation.

• Effluent is then transferred for secondary treatment.

(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 micropropagation termed as somaclones ?

(b) Mention two advantages of this technique.

What is mutualism? Mention any two examples where the organisms involved are commercially exploited in agriculture

List any four techniques where the principle of ex-situ conservation of biodiversity has been employed.

State what is apomixis. Comment on its significance. How can it be commercially used?