Differentiate between co-dominance and incomplete dominance. Give one example of each.

The collection of certain moths after industrialisation in England (1920), showed population of light winged less than that of dark winged moths, which was reverse of the observation made prior to industrialisation (1850s). Explain the observation made, with reference to Darwinian natural selection.

List any four devices that develop in angiosperms to encourage cross pollination. Mention the advantage of such devices.

How do normal cells sometimes become concerous? Why are malignant tumors so feared?

OR

(a) What does high ‘Biological Oxygen Demand’ (BOD) of a water body indicate?

(b) Explain the changes in BOD level of the primary effluent during its secondary treatment in sewage treatment tanks.

(a) Explain the principle on the basis of which DNA fragments separate in gel electrophoresis technique.

(b) How are the DNA fragments thus separated, visualised and isolated?