One day in 1676, a Dutch scientist named Antony van Leeuwenhoek looked through a microscope what no one had ever seen before: bacteria. Bacteria, very tiny living things, exist everywhere in the environment and can only be seen through a microscope.
On the one hand, bacteria are harmful. The word germs is used to describe harmful bacteria. Germs can cause terrible diseases such as cholera and tuberculosis. Cholera bacteria live in dirty water. If a person drinks the dirty water, the bacteria will infect his/her digestive system. Meanwhile, one who has tuberculosis bacteria in his/her lungs can transfer the diseases if he/she coughs or sneezes.
However, not all bacteria are harmful. Several bacteria help humans in many ways. For example, millions of good bacteria exist in the body’s digestive system. They help change the food we eat so our bodies can use vitamins in the food. Good bacteria are needed to make certain food such as cheeses and yogurts.
Bacteria also help the environment. For example, bacteria help breakdown dead plant materials such as fallen leaves so they can mix with the soil. Bacteria that exist in the ocean help in several ways. For example, they become food that is eaten by tiny fish. Then the tiny fish become food for big fish, and when you get a good catch of fish, they become your dinner.
Another way that bacteria help is by cleaning up oil spills from ships. Also, they help clean up human waste that rain carries into the ocean.
1. The text discusses … .
A. the advantages of good bacteria
B. the disadvantages of harmful bacteria
C. the advantages and disadvantages of bacteria
D. the good things about bacteria
E. the bad things about bacteria
2. Bacteria can only be seen through a microscope because they are … .
A. tiny
B. little
C. transparent
D. living
E. everywhere
3. What is the main idea of paragraph 3?
A. Bacteria exist in the digestive system
B. Some bacteria are good, some are not
C. Bacteria help change the food we eat
D. Some bactria are useful for humans
E. Bacteria are used to make food
4. How do bacteria help the environment?
A. By eating small fish
B. By living in dead plants
C. By mixing themselves with soil
D. By eating bigger fish
E. By cleaning up oil spills
5. The following are the advantages of bacteria, EXCEPT … .
A. They are needed to make certain foods
B. They will infect human’s digestive system
C. They help break down dead plant materials
D. They help clean up oil spills from ships
E. They help change the food people eat
6. From the text we know that … .
A. Bacteria live mostly in water
B. Cholera bacteria live in flowing water
C. Bigger fish feed on bacteria
D. Bacteria can only be seen through a microscope
E. Antony Van Leeuwenhoek discovered bacteria in 1670
