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托福聽力真題CH系列 004套

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Evolution of Fish

第1題

What is the main purpose of the lecture?

A To explain how biologists learned that not all mutations to a species are beneficial to the species

B To explain why biologists’ views about evolutionary adaptations have recently changed

C To explore the advantages and disadvantages of toxins as a defense against predators

D To discuss efforts to find ways to counteract a powerful toxin

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第2題

How is tetrodotoxin different from other animal toxins?

A It is equally toxic to all animals that come into contact with it.

B When heated, it can be safely consumed by people.

C It is poisonous only when combined with sodium.

D It is found in several different species of animal.

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第3題

What evidence suggests that puffer fish do not make tetrodotoxin themselves?

A They die if their nerve cells are exposed to tetrodotoxin for long periods of time. .

B They do not contain tetrodotoxin if they are raised in a controlled environment

C The steps that are necessary to produce tetrodotoxin are biologically complex.

D The chemicals required to synthesize tetrodotoxin are not found in ocean water

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第4題

What type of genetic mutations occurred in the evolution of certain animals that enabled them to become immune to tetrodotoxin?

A Mutations that prevent the toxin from blocking sodium ion transmissions

B Mutations that help the respiratory system fight off invasion by bacteria

C Mutations that prevent the animals from producing excessive amounts of the toxin

D Mutations that allow the animals to exist in bacteria-free environments

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第5題

What is the main point the professor makes when she mentions garter snakes?

A Garter snakes contain venom that is similar to the venom of scorpions.

B Tetrodotoxin can be synthesized by a wide variety of species.

C Resistance to tetrodofoxin has evolved in some animals that feed on animals containing the toxin.

D Tetrodotoxin may have spread to newts in North America as a newts to fend off certain predators.

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第6題

What is the professor’s opinion about the replication of evolutionary changes where the same changes occur in distinct species?

A She is convinced it is more frequent than Darwin thought possible.

B She doubts it will ever be conclusively found in the animal kingdom.

C She thinks examples that have been put forth could simply be random occurrences

D She wishes ther biologists were more open to the idea that it may occur.

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