2017年7月15日托福阅读真题+题目+答案：Poisonous Insects and the Birds that Eat Them

2017年7月15日托福阅读真题+题目+答案：Poisonous Insects and the Birds that Eat Them

Some insects contain poisons that do not affect an insect-eating bird until after the bird has swallowed one of them. Being swallowed is almost always fatal for these insects. How does an insect benefit by containing a poison that is effective only after it has been killed and eaten? This paradox is resolved once we realize that birds, which are made ill by the poison but are rarely killed by it, soon learn to recognize the warning signals of poisonous insects and reject them on sight. Eating a poisonous insect is an educational experience for predators, and thus the death of the insect victim serves to protect other members of its own species. If these other members of the species are relatives of the victim – perhaps its own offspring, siblings, or first cousins – their genetic makeup will be similar to the victim’s, and many of the victim’s genes will survive in them. In almost all organisms, including most insects other than bees or wasps, half of a victim’s genes will survive in any one of its offspring, half in a sister or brother, a quarter in a nephew or niece, and an eighth in a first cousin. Thus by sacrificing itself, a victim enhances the chances that its own genes will survive by improving the chances of the survival of its relatives.

1.The word “resolved” in the passage is closest in meaning to

A.settled

B.complicated

C.created

D.extended

2.According to paragraph 1, why is eating a poisonous insect an “educational experience” for predators?

A.It makes the predator less likely to become ill the next time it eats a poisonous insect.

B.It enables the predator to recognize and avoid similar types of insects.

C.It enables the predator to subsequently avoid eating the particular part of the insect where poison is stored.

D.It allows predators to warn their relatives of the dangers of consuming poisonous insects.

3.According to paragraph 1, the relatives of a poisonous insect that is eaten by a bird will

A.be more likely to be consumed by birds of the same species

B.have a better chance of survival

C.attempt to sacrifice themselves for the benefit of their own offspring

D.be unlikely to have offspring of their own

Some insects synthesize poisons within their own bodies. ▋Others store in their bodies poisons that are contained in plants that they eat. ▋Monarch butterflies contain toxic substances that they acquire from milkweed plants they eat when they are caterpillars. ▋ And these butterflies advertise their toxicity by means of their blatant black and orange warning colors.▋ The toxins from milkweeds, called cardenolides, are related to digitalis, which is used to treat heart disease, but these toxins can be fatal to birds in fairly low doses. Fortunately for an inexperienced bird that eats a monarch, milkweed cardenolides induce vomiting at a somewhat lower dose than the lethal dose and are thus usually eliminated before they kill the bird.

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