UNIT 04 Valley
Have you been to a nice valley between big mountains? If you see many mountains in your country, you also have many valleys. If you go to a very clean valley, you can find a lot of living things in valleys, such as crawfish, various small fish, and even otters. Crawfish can only live in very clean water. If you find a crawfish, that valley must be very fresh。
It is natural that children are curious (好奇的) about the world around them. For example, they want to
know how their hearts beat. They want to know why the ocean water tastes salty.
As children grow up, they become curious about different kinds of things. When they are babies, they
are interested in the parts of their bodies and in the smiles of their mothers. They become interested in the
physical world around them: the plants, the animals, the sky. Later, they become interested in the things that
people have made: wheels, bicycles, cars. And when they are adults, their curiosity continues. Sometimes this
curiosity leads to a career (生涯、职业) in science.
Scientists spend their lives trying to find out about the world. Those who work with the earth sciences
study the earth, the oceans, and the sky. Other scientists who study living things work with the biological
sciences. A third group of scientists study the physical sciences, e.g. physics, chemistry.
These scientists have already discovered a lot about our world. For example, they tell us why your heart
beats fast when you run. They say that when you are quiet, your heart normally beats sixty-five or seventy-
five times a minute. Your heart is a pump (泵) that pumps blood to all parts of the body. The blood carries
oxygen and nutrition. When you run, your muscles work very hard and use the nutrition that the blood carries
to them. The muscles need oxygen, too. So your brain sends a signal to the heart. The signal means that the
muscles need more nutrition and oxygen. Then the heart beats fast and sends blood quickly to the muscles.
It may beat 90 to 140 times a minute.
Of course, scientists cannot answer all of our questions. If we ask, "Why does the ocean water taste
salty" scientists will say that the salt comes from rocks. When a rock gets very hot or very cold, it cracks.
Rain falls into cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt
into the ocean. But then we ask, "What happens to the salt in the ocean? The ocean does not get saltier every
year." Scientists are not sure about the answer to this question.
We know a lot about our world, but there are still many answers that we do not have, and we are curious.
Select True or False
- According to the passage, which of the following statements is true?
❶ Crawfish don’t live in valleys. (T/F)
❷ There are many living things in valleys. (T/F)
A. People are curious in the same way.
B. People in different countries are interested in different things.
C. Men and women are curious about different things.
D. People of different ages are interested in different things
❸ Valleys are usually near the ocean. (T/F)
- Scientists who work with the biological sciences study ____.
More to know
A. the earth, the oceans and the sky
B. man-made things
C. plants and animals
D. ocean water
- When you run, your muscles need ____.
··You must be hungry。
A. more nutrition and oxygen
B. more signals
C. more salt
- People are always curious because ____.
··He must be at home。
A. they cannot explain many things
B. they know nothing about the world
C. they know little about the world
D. they want to be scientists
*Read and circle the best answer。
❶ What can you see if there are a lot of mountains in your country?
a. valleys b. oceans c. deserts
❷ What can you find if you go to a clean valley?
a. sand and water b. rocks and stones c. living things
*Complete the sentence with the right answer。
❸ can only live in very clean water。
a. Humans b. Wild animals c. Crawfish
❹ If you find a crawfish, that valley must be very 。
a. fresh b. dirty c. hard
DESCRIBE THE PICTURE
*Unscramble the words in the box。
the rock An otter on is