Explain the concept of congruence of figures with the help of certain examples.

Explain mutualism with the help of an example.

Explain the concept of direct variation.

Explain the concept of the Blue Revolution

Explain commensalism, with the help of an example.

(a) Explain the significance of ecological pyramids with the help of an example. (b) Why are the pyramids referred to as ‘upright’ or ‘inverted’? Explain.

Explain brood parasitism with the help of an example.

Explain the concept of the blue revolution .

Give the scientific name of the plant selected by Mendel for his experiments. State three laws given by him. Explain briefly the law of independent assortment with the help of an example. Define complementary genes. Explain it with the help of diagrammatic sketches.

What is commensalism' Explain with the help of an example.

Explain chemical energy with the help of two examples.