A carbon compound 'P' on heating with excess conc. H₂S0₄ forms another carbon compound 'Q' which on addition of hydrogen in the presence of nickel catalyst forms saturated carbon compound 'R'. One molecule of 'R' on combustion, forms two molecules of carbon dioxide and three molecules of water. Identify P, Q and R and write chemical equations for the reactions involved.

Describe an activity to show that the colours of white light splitted by a glass prism can be recombined to get white light by another identical glass prism. Also draw ray diagram to show the recombination of the spectrum of white light.

The activities of man had adverse effects on all forms of living organisms in the biosphere. Unlimited exploitation of nature by man disturbed the delicate ecological balance between the - living ' and non-living components of the biosphere. The unfavorable conditions created by man himself threatened the survival not only of himself but also the entire living organisms on the mother earth. One of your classmates is an active member of 'Eco-club' of your school which is creating. environmental awareness amongst the school students, spreading the same in the society and also working hard for preventing environmental degradation of the surroundings.

(a) Why is it necessary to conserve our environment?

(b) State the importance of green and blue dust-bins in the safe disposal of the household waste.

(c) List two values exhibited by your classmate who is an active member of Eco-club of your school.

What is placenta? Describe its structure. State its functions in case of a pregnant huma1n female.

Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.