Natural ways of keeping time

In ancient times, people had to use the sun and the moon to tell time. They got up when the sun came up and worked in the fields until the sun went down.

Man-made things

The sand clock is made of two glass balls joined by a narrow neck. The top ball was filled with sand. The sand slowly moved through the neck into the bottom ball. People knew how much time had passed when all the sand had fallen to the bottom ball.

People also made the water clock. They made a small hole near the bottom of a pot. Then they filled the pot with water. Markings inside the pot showed how much time passed as the water dripped (滴) out of the hole.

Nature’s Clocks in Living Things

◆Animals’ Body Clock

Animals do not need clocks to know time. They have a way of telling time by their bodies. Birds know when to fly to warmer places before winter. Some animals know when to keep more food for the cold winter months. Some fish know when it is time to move up the river and lay eggs.

◆Plants have their own clocks

Plants also have their own clocks to keep time. Plants know when to open flow­ers or when to drop their leaves.

◆The Body Clock in Human Beings

People also have their own body clocks. When we get used to our lives, our body clocks can be very accurate (准确的). It can tell us when it is time to wake up. It can also tell us when to eat or to go to sleep.

小题1:How could an ancient farmer know when to go back home in the daytime?

A．By looking at the moon.

B．By looking at the stars.

C．By looking at the sun.

D．By feeling whether tired or not.小题2: How many kinds of living things with nature’s clocks are mentioned here?

A．2.

B．3.

C．5

D．6.小题3:From the passage, we know what man-made things have in common is that_______.

A．both of them have a hole.

B．both of them are designed with glass balls.

C．both of them can be used only once.

D．both of them tell time in the same way