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Have you ever wondered how many ants there are on earth? Scientists at the University of Hong Kong certainly have. In a new study, they estimated the number of the world's ants is about 20,000,000,000,000,000 (20 with 15 zeroes)!
That means for every human, there are nearly 2.5 million ants. If you put all the ants on a scale(秤), they'd weigh more than all the wild birds and mammals on earth.
How did they count such a big number? In the past, many scientists counted ants in different areas. They collected fallen leaves and earth and dried them to force the ants to come out for counting. Based on 465 studies that cover all continents(大陆), the new study made the estimation.
According to Wang Runxi, one of the authors, the number and distribution(分布) of ants can be valuable predictors of environmental changes.
"Ants play an important role in the ecosystem," Wang told Science and Technology Daily. "They help loosen the soil, spread seeds, break down things and form a part of the food chain(食物链). They are everywhere on earth except for the coldest places."
"Compared with big animals, little ants are more sensitive(敏感的) to environmental changes," Wang added. Most ants live in tropical(热带的) and subtropical(亚热带的) areas. But in recent years, ants have been moving towards the two poles because of global warming. Changes in forests, such as too much logging(砍伐), also affect the number of ants, the study showed.
"Our global map of ants allows us to better understand and predict ants' responses to worrying environmental changes," scientists wrote in the study.
() 1. What does the study show about ants?
A. Ants actually belong to mammals.
B. There are more ants than humans.
C. Ants on earth weigh more than all other animals.
D. There are nearly 2.5 million ants on earth.
() 2. How did scientists count ants in different areas?
A. They counted the ants running on the ground.
B. They picked leaves from trees and counted ants on them.
C. They dried fallen leaves and earth to make ants come out.
D. They made a fire on the fallen leaves to count the dead bodies.
() 3. How has global warming affected ants in recent years according to Wang?
A. Many ants have moved to warm places.
B. More ants start to live in forests.
C. More ants are moving to the two poles.
D. The number of ants is going up.
() 4. What is the passage mainly about?
A. How heavy ants can be.
B. Why we should protect ants.
C. Studies on wild animals in the world.
D. Research on ants' number and importance.