RC Tortoise

[unifiedhand]

Despite its 1989 designation as a threatened species, the desert tortoise has declined in numbers by ninety percent since the 1980s. Although federal protection made it illegal to harm desert tortoises or remove them from the southwestern North American deserts, this measure has been insufficient to reverse the species’ decline. The lack of recovery is partly due to the desert tortoise’s low reproductive potential. Females breed only after reaching fifteen to twenty years of age, and even then may only lay eggs when adequate forage is available. The average mature female produces only a few eggs annually. From these precious eggs, hatchlings emerge wearing soft shells that will take five years to harden into protective armor. The vulnerable young are entirely neglected by adult tortoises, and only five percent ultimately reach adulthood.
Predators are blamed for a majority of tortoise deaths; ravens alone are estimated to cause more than half of the juvenile tortoise deaths in the Mojave Desert. Tortoise eggs and juveniles can also fall prey to mammals and other reptiles. For protection from predators, as well as from desert temperature extremes, tortoises of all ages burrow into the earth. However, if rabbits and rodents are scarce, larger predators may exhume tortoises from their burrows, devouring even mature tortoises despite their hardened shells. Further, tortoises are susceptible to a wide range of pathogens. The population decline is partly due to upper respiratory tract disease (URTD), characterized by nasal and ocular discharge and palpebral edema. In 2006, more than 80 percent of captive desert tortoises had anti-mycoplasma antibodies, seropositive indication of the disease. Released captive tortoises can rapidly spread URTD into the wild population with devastating consequences.
Though desert tortoises are well adapted to arid habitats, and adults can survive a year without access to water, they rely heavily on moisture in the vegetation consumed in spring, when they surface from their hibernal dormancy. The loss of native plants to grazing livestock and invasive plant species, then, may lessen the tortoise’s resistance to pathogens, though the tortoises do also dig precipitation basins in the soil and linger near one when rain is impending.


The author mentions "anti-mycoplasma antibodies" in the second paragraph in order to
claim that captive tortoises should not be released into the wild
refute claims that captive tortoises are more healthy than those in the wild
suggest an explanation for certain disease symptoms
emphasize how widespread a disease is in a population
discuss the effects of diet on the desert tortoise’s susceptibility to disease


So the official answer is D. I understand what they mean but the question was why do they mention "anti-mycoplasma antibodies" , not why do they mention "more than 80 percent of captive desert tortoises had anti-mycoplasma antibodies". The two are very different- yes I would agree if the question was the 2nd one then D would be correct. I could be reading into these to much but its hard to do that on some CR question where you really need to be word sensitive because any single word can change the whole thing completely. Thanks everyone

[tim]

which answer do you think is better? seriously, you're going to do MUCH better on the GMAT if you learn to pick the correct answers rather than trying to find flaws in the questions..

[aG627]

Hi,
I have a disagreement with the official explanation,given as below:

(D) CORRECT. The passage mentions the disease URTD as a contributor to the population decline and goes on to indicate that “in 2006, more than 80 percent of captive desert tortoises had anti-mycoplasma antibodies, seropositive indication of the disease [URTD].” The fact that URTD is so widespread supports the overall claim that the disease is a contributor to the population decline.

The passage states that more than 80% of the captive tortoises have URTD-> this doesnt mean that its is widespread among the total population ( captive + free). The passage dose not state the ratio of captive to free tortoises either, hence I eliminated the choice thinking the statement does not represent correctly how widespread the disease is.

Please help me clarify my understanding.
Thanks,
Avi

[CameronT327]

The passage states that more than 80% of the captive tortoises have URTD-> this doesnt mean that its is widespread among the total population ( captive + free). The passage dose not state the ratio of captive to free tortoises either

This was my thinking as well and what led to me selecting A because while A is a bit of an assumption (author doesn't actually make claim captive shouldn't be released) he does says captive tortoises are 80% infected with a contagious disease that is hurting the general population. But compared to D where, as Avi said, assuming 80% of captive tortoises suggests an equally high number among wild tortoises is a far greater assumption for which you have no evidence.

[wus89]

The explanation of (A): Although the passage states that “released captive tortoises can rapidly spread URTD into the wild population with devastating consequences,” it does not explicitly state that captive tortoises should not be released into the wild.

I think “released captive tortoises can rapidly spread URTD into the wild population with devastating consequences,” INFER captive tortoises should not be released into the wild because of the word " devastating consequences"

Can any expert help to explain why A wrong?
Thanks.

[Sage Pearce-Higgins]

Good discussion here; it's worth picking apart wrong answers to help yourself avoid them in the future. I've got a few comments to make:

-The question asks just why "anti-mycoplasma antibodies" are mentioned. Sure, although it doesn't mention the 80% stat, the point of mentioning the antibodies is to say something about them: here, that means a stat about captive tortoises.
-Be aware of the story of the passage: sentences connect together logically. Previously we're told that 'tortoises are susceptible to a wide range of pathogens'. The stat about the antibodies is support for this claim, in the form of an example.
-Answer choice A is a trap. We need to be aware of the difference between a purpose question (why is the author writing this?) and an inference question (what is implied by these statements?). Answer A is more on the side of an inference, although, as CameronT327 says, there's a weakness in the logic here. The overall tone of the passage is descriptive, not argumentative. Try this for a task: think up a suitable title for the passage. Nowhere does the author make claims about the best way to save the tortoise.