Although some animals exhibit a mild skin reaction to urushiol, an oi

Question

Although some animals exhibit a mild skin reaction to urushiol, an oil produced by plants such as poison oak and poison ivy, it appears that only humans develop painful rashes from touching it. In fact, wood rats even use branches from the poison oak plant to build their nests. Therefore, urushiol probably did not evolve in these plants as a chemical defense.

Which one of the following, if true, adds the most support for the conclusion of the argument?

A. Wood rats build their nests using dead, brittle branches, not live ones.
B. A number of different animals use poison oak and poison ivy as food sources.
C. It is common for plants to defend themselves by producing chemical substances.
D. In approximately 85 percent of the human population, very small amounts of urushiol can cause a rash.
E. Poison oak and poison ivy grow particularly well in places where humans have altered natural forest ecosystems.

MartyMurray · Answer

Explanation

Although some animals exhibit a mild skin reaction to urushiol, an oil produced by plants such as poison oak and poison ivy, it appears that only humans develop painful rashes from touching it. In fact, wood rats even use branches from the poison oak plant to build their nests. Therefore, urushiol probably did not evolve in these plants as a chemical defense.

The conclusion of the argument is the following:

urushiol probably did not evolve in these plants as a chemical defense

The support for the conclusion is the following:

it appears that only humans develop painful rashes from touching it. In fact, wood rats even use branches from the poison oak plant to build their nests.

The reasoning of the argument is that, since most animals do not develop painful rashes from touching urushiol, plants must not have developed it to defend themselves. After all, something that plants use to defend themselves would likely give many animals rashes to protect plants effectively. Also, presumably, a defense mechanism would prevent animals from doing things such as using branches of plants that produce it to build nests.

Which one of the following, if true, adds the most support for the conclusion of the argument?

The correct answer will add additional support for the conclusion.

A. Wood rats build their nests using dead, brittle branches, not live ones.

This choice does the opposite of what we need.

After all, if wood rats use dead branches to build their nests, then the fact that they use branches from poison oak to build their nests doesn't indicate that urushiol is not produced to defend plants. It could be instead that the plants protect themselves when they are alive using urushiol, and then later, rats collect dead parts of the plants that the plants don't need to defend.

So, this choice reduces, rather than adds, support for the conclusion that urushiol did not evolve as a defense.

Eliminate.

B. A number of different animals use poison oak and poison ivy as food sources.

This choice is interesting.

We already know that urushiol doesn't seem to be a defense mechanism because animals can touch it without getting rashes. Now, this choice tells us that animals eat it.

Common sense tells us that being eaten is one of the primary things that plants would defend themselves against. So, if urushiol doesn't stop animals from eating these plants that produce it, then it's not defending the plants well at all and thus probably "did not evolve in these plants as a chemical defense."

So, this choice provides addtional support for the conclusion.

Keep.

C. It is common for plants to defend themselves by producing chemical substances.

If anything the fact that plants defend themselve by producing chemical substances is a reason to believe that urushiol could also be produced by plants for the purpose of defending themselves.

So, this choice slightly weakens the case for the conclusion.

Eliminate.

D. In approximately 85 percent of the human population, very small amounts of urushiol can cause a rash.

If anything, the fact that even small amounts of urushiol cause rashes in most humans indicates that the chemical is meant for defense. After all, a chemical the causes a rash in most people even in small amounts would be great for defending a plant.

So, if anything, this choice weakens, rather than strengthens, the support for the conclusion.

Eliminate.

E. Poison oak and poison ivy grow particularly well in places where humans have altered natural forest ecosystems.

This choice has no clear effect on the argument.

Honestly, when I first read this choice, I started making up a story in my mind about how, if poison oak and poison ivy grow well where humans have altered things, then maybe these plants don't deal with nature and animals well and therefore don't defend themselves well. So. maybe urushiol is not for defense.

However, the truth is that the fact that these plants grow well where things have been "altered," meaning "changed," doesn't clearly indicate anything about their defense systems. After all, they could use defense systems in a variety of situations, regardless of whether those situations are altered ones. After all, altered situations could involve plenty of things for plants to defend themselves against.

Eliminate.

Correct answer:  B

naveeng15 · Answer

We already know that urushiol doesn't seem to be a defense mechanism because animals can touch it without getting rashes. Now, this choice tells us that animals eat it.

Common sense tells us that being eaten is one of the primary things that plants would defend themselves against. So, if urushiol doesn't stop animals from eating these plants that produce it, then it's not defending the plants well at all and thus probably "did not evolve in these plants as a chemical defense."

So, this choice provides addtional support for the conclusion.

unraveled · Answer

Although some animals exhibit a mild skin reaction to urushiol, an oil produced by plants such as poison oak and poison ivy, it appears that only humans develop painful rashes from touching it. In fact, wood rats even use branches from the poison oak plant to build their nests. Therefore, urushiol probably did not evolve in these plants as a chemical defense.

Which one of the following, if true, adds the most support for the conclusion of the argument?

A. Wood rats build their nests using dead, brittle branches, not live ones. - WRONG. Indirectly weakens. 
B. A number of different animals use poison oak and poison ivy as food sources. - CORRECT. Food tells us that the chemical is not effective to those use eat it. Supports.
C. It is common for plants to defend themselves by producing chemical substances. - WRONG. Generic statement that does not address the case specific.
D. In approximately 85 percent of the human population, very small amounts of urushiol can cause a rash. - WRONG. Seems the other way rounds as a defense by plant.
E. Poison oak and poison ivy grow particularly well in places where humans have altered natural forest ecosystems. - WRONG. Growing well does nothing to the passage as in it neither supports nor weakens the argument i.e. the chemical acts as defense.

Answer B.

LamboWalker · Answer

Uroshoil only causes rashes to humans, not other animals. Therefore, the presence of uroshoil is probably not as a chemical defense in these plants. We are to support this argument.

A. Wood rats build their nests using dead, brittle branches, not live ones. 
This is weakening the argument.

B. A number of different animals use poison oak and poison ivy as food sources. 
Correct. These plants are being eaten by these animals yet the plants didn't 'evolve' anything in them that might prevent the plants from being eaten.

C. It is common for plants to defend themselves by producing chemical substances. 
This is weakening the argument if anything.

D. In approximately 85 percent of the human population, very small amounts of urushiol can cause a rash. 
Adds a fact that does not do anything to the argument.

E. Poison oak and poison ivy grow particularly well in places where humans have altered natural forest ecosystems. 
Took me a while, but this statement adds nothing to the argument really. Plus B is a much better choice.

kakarot10 · Answer

The conclusion states that the poison ivy didn't evolve its chemical defence enough to defend itself from animals. Statement B states that animals consume poison ivy, which indirectly tells that chemical defense of ivy isn't strong enough , therefore it gets eaten . So answer is B

VerbalBot · Answer

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Although some animals exhibit a mild skin reaction to urushiol, an oi

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