Night of the Living Ants When an ant dies,other ants move th..

第1题

Night of the Living Ants When an ant dies,other ants move the dead insect out of the nest.

Night of the Living Ants

When an ant dies，other ants move the dead insect out of the nest．This behavior. is interesting to scientists，who wonder how ants know for sure-and so soon-that another ant is dead．

Dong-Hwan Choe，a scientist at the University of California，found that Argentine ants have a chemical on the outside of their bodies that signals to other ants，“I’m dead-take me away．”

But there's a twist to Choe's discovery．Choe says that the living ants-not just the dead ones -have this death chemical．In other words，while an ant crawls around，perhaps in a picnic or home，it's telling other ants that it's dead．

What keeps ants from hauling away the living dead?Choe found that Argentine ants have two additional chemicals on their bodies，and these tell nearby ants something like，“Wait-I'm not dead yet．” So Choe's research turned up two sets of chemical signals in ants：one says，“I'm dead，”the other set says，“I'm not dead yet．”

Other scientists have tried to figure out how ants know when another ant is dead．If an ant is knocked unconscious，other ants leave it alone until it wakes up．That means ants know that unmoving ants can still be alive．

Choe suspects that when an Argentine ant dies．the chemical that says“Wait-I'm not dead yet” quickly goes away．Once that chemical is gone，only the one that says“I'm dead”is left．“It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard(墓地)，not because its body releases new，unique chemicals after death，”said Choe．When other ants detect the“dead”chemical without the“not dead yet”chemical，they haul away the body．This was Choe's hypothesis(假设)．

To test his hypothesis，Choe and his team put different chemicals on Argentine ant pupae(蛹)． When the scientists used the“I'm dead”chemical，other ants quickly hauled the treated pupae away． When the scientists used the“Wait-I'm not dead yet”chemical，other ants left the treated pupae alone． Choe believes this behavior. shows that the“not dead yet”chemical overrides(优胜于)the“dead”chemical when picked up by adult ants．And that when an ant dies，the“not dead yet”chemical fades away． Other nearby ants then detect the remaining“dead”chemical and remove the body from the nest．

The phrase“this death chemical”in paragraph 3 refers to

A．the chemical that contains poison．

B．the chemical that announces death．

C．the chemical that prevents death．

D．the chemical that causes death．

点击查看答案

第2题

When evaluating the size of the deadweight loss due to a tax we know that the ( )

A、greater the elasticities of supply and demand, the greater the deadweight loss.

B、smaller the elasticities of supply and demand, the greater the deadweight loss.

C、greater the decrease in both quantity demanded and quantity supplied, the greater the deadweight loss.

D、primary factor that determines the size of the deadweight loss in the percentage tax is of price.

点击查看答案

第3题

Read the sentences and choose the correct ones. Brenda has just moved to a new school and has made a new friend, Paula. They are sitting in a snack bar after school talking. Paula asks Brenda," Tell me about your family." Brenda: "My family is a rather small one, with only three people, my father, my mother and me. My father is a doctor. My mother is a teacher. My mother is very patient and understanding while my father is not very patient. He is often quite loud and wants things to happen at once. We love each other very much. Although sometimes we might fight about things we feel strongly about, very soon we will change the subject and discuss something else. We're a happy family. How about you? Paula: "I have a big family with seven people, my grandparents, parents, two older brothers and me. We all live together in a big house. It is often very noisy in our house, especially at dinner time. Grandfather has a loud voice. But it is nice having my grandparents living with us. That means that when I come home from school there is always somebody there for me. We take care of one another, share housework, and often communicate all together. My brothers help me with problems I have with homework and I help them with problems they have with girls."

A、Brenda's father is patient.

B、Brenda is patient.

C、Brenda's mother is a patient.

D、Brenda's mother is patient.

点击查看答案

第4题

In the animal rights (), much is made of the volume of pain these animals () in the name of medical science. Activists deny that we are trying to help and say it is () of our evil and cruel (). A more reasonable argument, however, can be advanced in our (). Life is often () to animals and human beings. Teenagers are flung from trucks and suffer severe head (). Young children () able to walk find themselves at the bottom of swimming pools while a parent is occupied with something else. From everyday germs to gang (), no life is free of pain. Physicians hoping to relieve the eternal suffering of these tragedies have only three choices: 1) create an animal model of the problem to understand the process and test new therapies; 2) experiment on human beings (some experiments will succeed, most will fail); or 3) leave medical knowledge static, hoping that () discoveries will lead us forward.

点击查看答案

第5题

Night of the Living Ants When an ant dies,other ants move the dead insect out of the nest.

Night of the Living Ants

When an ant dies，other ants move the dead insect out of the nest．This behavior. is interesting to scientists，who wonder how ants know for sure-and so soon-that another ant is dead．

Dong-Hwan Choe，a scientist at the University of California，found that Argentine ants have a chemical on the outside of their bodies that signals to other ants，“I’m dead-take me away．”

But there's a twist to Choe's discovery．Choe says that the living ants-not just the dead ones -have this death chemical．In other words，while an ant crawls around，perhaps in a picnic or home，it's telling other ants that it's dead．

What keeps ants from hauling away the living dead?Choe found that Argentine ants have two additional chemicals on their bodies，and these tell nearby ants something like，“Wait-I'm not dead yet．” So Choe's research turned up two sets of chemical signals in ants：one says，“I'm dead，”the other set says，“I'm not dead yet．”

Other scientists have tried to figure out how ants know when another ant is dead．If an ant is knocked unconscious，other ants leave it alone until it wakes up．That means ants know that unmoving ants can still be alive．

Choe suspects that when an Argentine ant dies．the chemical that says“Wait-I'm not dead yet” quickly goes away．Once that chemical is gone，only the one that says“I'm dead”is left．“It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard(墓地)，not because its body releases new，unique chemicals after death，”said Choe．When other ants detect the“dead”chemical without the“not dead yet”chemical，they haul away the body．This was Choe's hypothesis(假设)．

To test his hypothesis，Choe and his team put different chemicals on Argentine ant pupae(蛹)． When the scientists used the“I'm dead”chemical，other ants quickly hauled the treated pupae away． When the scientists used the“Wait-I'm not dead yet”chemical，other ants left the treated pupae alone． Choe believes this behavior. shows that the“not dead yet”chemical overrides(优胜于)the“dead”chemical when picked up by adult ants．And that when an ant dies，the“not dead yet”chemical fades away． Other nearby ants then detect the remaining“dead”chemical and remove the body from the nest．

The phrase“this death chemical”in paragraph 3 refers to

A．the chemical that contains poison．

B．the chemical that announces death．

C．the chemical that prevents death．

D．the chemical that causes death．

点击查看答案