3. Life on Earth
1. Answer each question in one sentence.
(a) What instrument do we need to see a unicellular organism?
Ans. We need a microscope to see a unicellular organism.
(b) Where did the protozoa appear first?
Ans. It is believed that protozoa first appeared in water.
2. Answer the following in brief.
(a) How were the sun and the planets in our solar system created?
Ans. Around 4.5 billion years ago, an enormous cloud of very hot gases and dust spinning at a great speed was formed in space. Its circular motion and great speed caused it to divide into several portions thus creating the sun and the planets which revolve around the sun.
(b) Write any two characteristics of animals.
Ans. Two characteristics of animals are:
(i) Animals breathe.
(ii) Animals move in order to get food or for other purposes.
3. Find the names of the planets in the box below.
4. Arrange the events given below in the chronological order.
(a) Water bodies appeared on the Earth’s surface.
(b) The sun and the planets revolving around it were created.
(c)Protozoa appeared in water.
(d)) An enormous cloud of hot gases and dust was formed in space.
Ans. (i) An enormous cloud of hot gases and dust was formed in space.
(ii) The sun and the planets revolving around it were created.
(iii) Water bodies appeared on the Earth’s surface.
(iv) Protozoa appeared in water.