Which one of the following is responsible for the sustenance of underground water?

Answer question numbers 3(a) to 3(d) and 4(a) to 4(d) on the basis of your understanding of the following paragraphs and the related studied concept.

The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organism increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on. Some degree of sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of the population.

(a)List two common signs of sexual maturation in boy and girls.

(b) What is the result of reckless female foeticide?

(c) Which contraceptive method changes the hormonal balance of the body?

(d) Write two factors that determine the size of the population.

Human body is made up of five important components, of which water which the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body

(a) Why is the maximum concentration of pesticides found in human beings?

(b) Give one method which could be applied to reduce our intake of pesticides through food to some extent.

(c) Various steps in a food chain represent:

(a) Food web (b) Trophic level

(c) Ecosystem (d) Biomagnification

(d) With regard to various food chains operating in an ecosystem, man is a:

(a) Consumer (b) Producer

(c) Producer and consumer (d) Producer and decomposer

Incomplete combustion of coal and petroleum:

(A) increases air pollution.

(B) increases efficiency of machines.

(C) reduces global warming

(D) produce poisonous gases

The correct option is :

When sodium hydrogen carbonate is added to ethanoic acid a gas evolves. Consider the following statements about the gas evolved?

(A) It turns lime water milky.

(B) It is evolved with a brisk effervescence.

(C) It has a smell of burning sulphur.

(D) It is also a by-product of respiration. The correct statements are: