“The sex of the children is determined by what they inhert from their father and not their mother.” Justify.
(b) Give an example where environmental factors like temperature determines the sex of the offspring.

Dams are useful for the society but there is public opposition to the construction of large dams. Justify your answer by giving three problems.

Write chemical equations for what happens when
(i) sodium metal is added to ethanoic acid.
(ii) solid sodium carbonate is added to ethanoic acid.
(iii) ethanoic acid reacts with a dilute solution of sodium hydroxide.

The atomic number of an element is 16. Predict

the number of valence electrons in its atom;
its valencies;
its group number;
whether it is a metal or a non-metal;
the nature of oxide formed by it;
the formula of its chloride.

An object is placed between infinity and the pole of a convex mirror. Draw a ray diagram and also state the position, the relative size and the nature of the image formed.

What is the principle of reversibility of light? Show that the incident ray of light is parallel to the emergent ray of light when light falls obliquely on a side of-a rectangular glass slab.

What eye defect is myopia? Describe with a neat diagram how this defect of vision can be corrected by using a suitable lens.

What does HIV stand for? Is AIDS an infectious disease? List any four modes of spreading AIDS.

A team of Indian researchers went to Antarctica to study the ozone layer. They confirmed the presence of largest ozoye hole over Antarctica and was just short of 27 million sq. km. After few days of their return, one of the scientists developed rashes, burning sensation and other skin problems which the doctors have confirmed as skin cancer.
(a) What may be the cause of cancer just after return from Antarctica?
(b) What do we learn from this incident?
(c) Raghav, a student of your school organises a poster-making competition on the topic ‘Save Ozone’. What moral value is shown by Raghav? What other initiatives will you suggest in this regard?

With the help of suitable diagrams, explain the various steps of budding in Hydra.