GMAT Prep Strengthen : In polluted environments, dolphins g

[JbhB682]

Source : GMAT prep

In polluted environments, dolphins gradually accumulated toxins in their body fat, and the larger the dolphin the more accumulated toxin it can tolerate. Nearly 80 percent of the toxins a female dolphin has accumulated pass into the fat-rich milk her nursing calf ingests. Therefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida’s Gulf Coast is probably the result of their being poisoned by their mother’s milk.

Which of the following, if true, most strengthens the argument?

(A) The survival rate of firstborn dolphin calves in the area along Florida’s Gulf Coast is highest for those whose mothers were killed before they were weaned.

(B) The rate at which adult dolphins living in the waters along Florida’s Gulf Coast accumulate toxins is no higher than that of adult dolphins in comparably polluted waters elsewhere.

(C) Among dolphin calves born in the area along Florida’s Gulf Coast, the mortality rate is highest among those with living siblings.

(D) As dolphins age, they accumulate toxins from the environment more slowly than when they were young.

(E) Dolphins, like other marine mammals, have a higher proportion of body fat than do most land mammals.

[JbhB682]

Hello - is my reasoning for cancelling out E specifically accurate ?

My thinking on E
- Dolphins have a higher proportion of body fat than do most land mammals.

Lets assume the proportion of body fat for dolphins is approximately 51 % whereas for land animals it is 30 % (lets assume)

This shows that most likely dolphin calves die at a larger rate from breast milk in comparison to calves of land animals from breast milk.

BUT the statement in blue does no strengthen the CAUSE mentioned in the argument which is

Breast Milk is the cause of death for dolphin calves.

Is this how how you eliminate E ?

[Sage Pearce-Higgins]

I think your reasoning is unnecessarily complicated. Your logic runs:

Lets assume the proportion of body fat for dolphins is approximately 51 % whereas for land animals it is 30 % (lets assume)
This shows that most likely dolphin calves die at a larger rate from breast milk in comparison to calves of land animals from breast milk.

That's a big jump! Sure, there's a relation between body fat and contaminated breast milk in dolphins, but we don't know that more body fat means more contamination of breast milk. We also don't know what happens in other animals: it's a big assumption to say that the same relationship occurs in other animals.

Keep your eye on the conclusion: here we're concerned with young dolphins dying in Florida. A comparison between dolphins and land mammals isn't relevant to that claim.

[JbhB682]

Hi Sage - thank you for following up.

Upon review of the conclusion specifically.

Is the conclusion saying this in your view ?

Mortality rate of Dolphin calves in the Florida Gulf Coast is higher compared to mortality rate of Dolphin calves in other industrial contaminated waters ?


I think my initial read on the conclusion was

Mortality rate of Dolphin calves in the Florida Gulf Coast is higher compared to Mortality rate of Dolphin calves in non industrial contaminated waters

[Sage Pearce-Higgins]

We don't need to have an opinion about the conclusion - take the conclusion as actually stated in the argument!

Therefore, the unusually high mortality rate among dolphin calves in the industrially contaminated waters along Florida’s Gulf Coast is probably the result of their being poisoned by their mother’s milk.

Sure, we could question what 'unusually high' is being compared to, but it's precise enough just to think 'other dolphins in general'.

[JbhB682]

Here was my attempt to eliminate B -- is this the right way to eliminate B ?

B states, the rate at which adult dolphins living in the waters along Florida's Gulf Coast accumulate toxins is no higher than that of adult dolphins in comparably polluted waters elsewhere

This basically just says adult dolphins living in FL's gulf coast absorbs toxins at a rate no higher than that of adult dolphins elsewhere with the same amount of pollution

This does not imply that whales (in the polluted FL gulf coast) vs. whales (in other polluted waters) have the same mortality rate however.

Given B doesn't touch upon mortality rates specifically between whales in the polluted FL gulf coast vs. mortality rates of whales in other polluted waters -- this doesn't do much to strengthen the argument

[esledge]

This does not imply that whales (in the polluted FL gulf coast) vs. whales (in other polluted waters) have the same mortality rate however.

Given B doesn't touch upon mortality rates specifically between whales in the polluted FL gulf coast vs. mortality rates of whales in other polluted waters -- this doesn't do much to strengthen the argument

You might mean dolphins here, but you've written whales. Anything about whales would be irrelevant (like E, which mentions "other marine mammals"). That said,

Here was my attempt to eliminate B -- is this the right way to eliminate B ?

B states, the rate at which adult dolphins living in the waters along Florida's Gulf Coast accumulate toxins is no higher than that of adult dolphins in comparably polluted waters elsewhere

This basically just says adult dolphins living in FL's gulf coast absorbs toxins at a rate no higher than that of adult dolphins elsewhere with the same amount of pollution

I agree with this paraphrase of (B). I think you are right that the connection to mortality rates is missing/unknown, and in GMAT-land that means it does nothing to the conclusion.

I'd also note that (B) can also be paraphrased as "The FL gulf coast is not unique when it comes to adult dolphin toxin absorption rates." Thus, if anything, this weakens the argument that "the unusually high mortality rate among dolphin calves" in that location can be explained by that location's adult dolphin toxin absorption (and subsequent passing of toxins to nursing calves).

To make a conclusion about a specific place, it helps the argument if that specific place is unique in some relevant way; (B) does the opposite.