Poisonous Insects and the Birds that Eat Them

Paragraph 1：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. 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. 

 

 

 

2. 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 

 

 

 

 

 

Paragraph 2：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. 

 

 

3. According to paragraph 2, why are monarch butterflies colored black and orange? 

 

A. To look like poisonous plants 

 

B. To blend in with plant life found in their habitat 

 

C. To advertise their transition from the caterpillar stage 

 

D. To signal to potential attackers that they contain poisons

 

 

 

4. What can be inferred from paragraph 2 about the toxic substances stored in the bodies of monarch butterflies? 

 

A. They are sometimes toxic to humans as well as to birds 

 

B. They are likely to kill inexperienced birds but not experienced birds 

 

C. They are usually vomited by birds before they can cause death.

 

D. They usually have no effect on birds when eaten in small amounts. 

 

 

 

 

 

Paragraph 3：Researchers have demonstrated that these poisons benefit monarchs. Researchers raised some monarch caterpillars on species of milkweed that do not contain cardenolides and others on milkweeds that do contain them. Captive blue jays, confined long enough to forget any previous experience that they may have had with a toxic monarch in nature, readily ate monarchs raised on poison-free plants. They continued to eat nontoxic monarchs as long as they were offered. Other jays readily ate monarchs that had been raised on toxin-containing plants, but soon thereafter they showed obvious signs of distress. They erected their crests, fluffed out their feathers, and vomited. After that one bad experience, they refused to eat either toxic or nontoxic monarchs. 

 

 

 

5. In paragraph 3, why does the author discuss an experiment in which researchers raised monarch caterpillars on two different species of milkweed? 

 

A. To prove that monarchs are able to consume plants that are poisonous to other species 

 

B. To support the claim that consuming poisonous milkweed is advantages to monarchs

 

C. To determine the amount of poison that is toxic to monarch butterflies 

 

D. To argue that most birds can consume poisonous insects without dying 

 

 

 

6. According to paragraph 3, jays that consumed toxin-containing monarchs reacted in all of the following ways EXCEPT by 

 

A. demonstrating symptoms of illness 

 

B. refusing to eat other toxic monarchs 

 

C. consuming only nontoxic monarchs in the future

 

D. fluffing out their feathers immediately after consuming 

 

 

 

 

 

Paragraph 4：Poisonous insects are seldom deadly to birds or other predators. An insect’s survival fitness is not enhanced if it kills the bird that eats it. Indeed, the victim benefits if the predator survives after devouring the victim and becoming aware of its poisonous properties. Most birds, like the majority of predators, are territorial. They live in a small and delimited area from which they exclude members of their own species other than their mates. If the poisonous insect, the bird’s victim, belongs to a species that does wander widely, its surviving relatives will probably live within, or at least pass through, the territory of this bird, which will leave them alone because it has been taught not to attack them by the sacrifice of their relative. But if the territory-holding bird is killed, it will almost immediately be replaced by a wandering member of its own species, a floater that is still searching for a territory of its own. When an experienced predator that has learned not to attack the insects in question is replaced by a floater that happens to be inexperienced, the relatives of the insect victim do not benefit from its sacrifice. Thus protective systems based on benign poisons are far more likely to evolve and persist than systems based on deadly poisons. 

 

 

7. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. 

 

A. A bird that has eaten a poisonous insect will learn to avoid relatives of the insect victim that move through or live in the bird’s territory.

 

B. A bird that eats insects will not attack poisonous insects living within its own territory but will attack insects that wander in from other territories. 

 

C. A territorial bird learns to avoid poisonous insects, making it more likely that the bird will have surviving relatives within its own territory. 

 

D. Poisonous insects are unlikely to become the victims of birds and thus are able to wander widely from one bird’s territory to another bird’s territory. 

 

 

 

8. What can be inferred from paragraph 4 about protective systems based on deadly poisons? 

 

A. They are less common than nondeadly systems in nature

 

B. They are more effective than systems based on nondeadly poisons. 

 

C. They are less common in insects than in other types of animals. 

 

D. They are most likely to be found in nonterritorial species. 

 

 

 

 

 

Paragraph 2：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. 

 

 

 

9. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? 

 

Certain ladybugs, for example, have a mechanism for producing poison.

 

 

 

 

 

10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selected THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. 

 

Many insects contain poisons that are not deadly to the birds that eat them. 

 

 

 

Answer Choices: 

 

A. While the poisons in toxic insects are not strong enough to kill the birds that eat them, they do result in survival advantages to future generations of those insects. 

 

B. Some toxic insects have evolved protective systems that allow them to survive being swallowed by birds, thereby ensuring both their own survival and that of their relatives. 

 

C. Since the genetic makeup of monarchs differs from other insects, like bees and wasps, the sacrifice of a monarch results in more of the victim’s genes surviving in its offspring 

 

D. Some insects, such as the monarch butterfly, store poisons in their bodies to discourage predators, while other insects make their own poisons. 

 

E. Research has shown that after a bad experience with toxic monarchs, a blue jay protects other members of its species by communicating a warning against eating them. 

 

F. The territorial nature of birds means that poisonous insects can move freely through a bird’s territory after the bird has learned to avoid them. 

 

 

答案请付费后查阅：