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A recent study has provided clues to predator-prey dynamics in the lat
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31 Mar 2022, 09:26
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A recent study has provided clues to predator-prey dynamics in the late Pleistocene era. Researchers compared the number of tooth fractures in present-day carnivores with tooth fractures in carnivores that lived 36,000 to 10,000 years ago and that were preserved in the Rancho La Brea tar pits in Los Angeles. The breakage frequencies in the extinct species were strikingly higher than those in the present-day species.
In considering possible explanations for this finding, the researchers dismissed demographic bias because older individuals were not over represented in the fossil samples. They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits. They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data. The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores—in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.
Question 1
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1. The primary purpose of the passage is to
(A) present several explanations for a well-known fact (B) suggest alternative methods for resolving a debate (C) argue in favor of a controversial theory (D) question the methodology used in a study (E) discuss the implications of a research finding
Question 2
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2. According to the passage, compared with Pleistocene carnivores in other areas, Pleistocene carnivores in the La Brea area
(A) included the same species, in approximately the same proportions (B) had a similar frequency of tooth fractures (C) populated the La Brea area more densely (D) consumed their prey more thoroughly (E) found it harder to obtain sufficient prey
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3. According to the passage, the researchers believe that the high frequency of tooth breakage in carnivores found at La Brea was caused primarily by
(A) the aging process in individual carnivores (B) contact between the fossils in the pits (C) poor preservation of the fossils after they were removed from the pits (D) the impact of carnivores’ teeth against the bones of their prey (E) the impact of carnivores’ teeth against the bones of other carnivores during fights over kills
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4. The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that
(A) the older an individual carnivore is, the more likely it is to have a large number of tooth fractures (B) the average age at death of a present-day carnivore is greater than was the average age at death of a Pleistocene carnivore (C) in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as did younger individuals (D) the methods used to determine animals’ ages in fossil samples tend to misidentify many older individuals as younger individuals (E) data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores
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5. According to the passage, if the researchers had NOT found that two extinct carnivore species were free of tooth breakage, the researchers would have concluded that
(A) the difference in breakage frequencies could have been the result of damage to the fossil remains in the La Brea pits (B) the fossils in other Pleistocene sites could have higher breakage frequencies than do the fossils in the La Brea pits (C) Pleistocene carnivore species probably behaved very similarly to one another with respect to consumption of carcasses (D) all Pleistocene carnivore species differed behaviorally from present-day carnivore species (E) predator densities during the Pleistocene era were extremely high
Question 6
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6. The passage suggests that tooth fractures in Pleistocene carnivores probably tended to occur less frequently
(A) during periods in which more prey were available (B) at sites distant from the La Brea area (C) in older individual carnivores (D) in species that were not preserved as fossils (E) in species that regularly stole carcasses from other species
Re: A recent study has provided clues to predator-prey dynamics in the lat
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31 Mar 2022, 10:15
1
1. A. Last paragraph implies that if the prey was scarce then the predator had more contact with the prey's bone. 2. B 5th line of the 2nd paragraph states this. 3. D The last few lines of paragraph 2 points to this. The rest of the options were all dismissed by the scientists. 4. D The premise of rejecting the hypothesis of not enough older samples breaks if this option were true. If the method of identifying younger from older was faulty and identified older dinos as younger, then there were clearly more older dinos among the samples under study. 5. A If either or both of those samples had breakage, then it would be possible that there was some damage done by the pits that stored the fossils for all of these years. 6. A Last paragraph says that prey was "seasonally available". Therefore, there were periods when prey was more available and periods when there was few or maybe none.
Re: A recent study has provided clues to predator-prey dynamics in the lat
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26 Jun 2022, 04:48
I got confused in number 3 between D and E. "Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities." D also has evidence. "The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores—in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species."
Can you please explain me.
And for Q no 1. How can we say that the passage is about implication. I saw all the faults of the theory stated in first paragraph. I cannot argue with other options too.
Re: A recent study has provided clues to predator-prey dynamics in the lat
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26 Jun 2022, 06:22
Expert Reply
When on my mobile I read carcass consumption I thought something about me
1 . The author is concerned with the implications of the findings which is suggested in the following lines.. "Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities " Hence option (E) is the right answer.
2 . "They ruled out local bias because breakage data obtained from other Pleistocene sites were similar to the La Brea data" The above excerpt suggests that both carnivores had similar breakage patterns and thereby similar frequency in tooth fractures. Hence option (B) is the right answer.
3. "The explanation they consider most plausible is behavioral differences between extinct and present-day carnivores—in particular, more contact between the teeth of predators and the bones of prey due to more thorough consumption of carcasses by the extinct species." Answer D
4. the methods used to determine animals’ ages in fossil samples tend to misidentify many older individuals as younger individuals
Answer D
5. "They rejected preservational bias because a total absence of breakage in two extinct species demonstrated that the fractures were not the result of abrasion within the pits." Answer A
6. Such thorough carcass consumption implies to the researchers either that prey availability was low, at least seasonally, or that there was intense competition over kills and a high rate of carcass theft due to relatively high predator densities.
A recent study has provided clues to predator-prey dynamics in the lat
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26 Jun 2022, 06:23
Expert Reply
As for question 4, refer to this portion: "the researchers dismissed demographic bias because older individuals were not over represented in the fossil samples." We can infer that demographic bias has to do with age differences. More specifically, if all of the fossils were from OLDER individuals, then the high proportion of tooth fractures might simply be a result of the aging process . In other words, in order to accurately compare the fossil teeth to the teeth of present-day predators, we need samples representing all ages in both groups.
With that in mind, let's consider the choices:
Quote:
4. The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that
A. the older an individual carnivore is, the more likely it is to have a large number of tooth fractures - This explains why we could have demographic bias if older individuals WERE over represented in the fossil samples. However, we are told that older individuals were NOT over represented, so (A) can be eliminated.
B. the average age at death of a present-day carnivore is greater than was the average age at death of a Pleistocene carnivore - If the OPPOSITE were true, that might hurt the author's argument by suggesting that the higher frequency of fractures among Pleistocene carnivores is a result of their longer life spans. As written, choice (B) gives us more reason to suspect that the fractures are not related to age (since the group that lived longer had fewer fractures). Regardless, the author is simply asserting that older individuals were not over represented in the fossils. Choice (B) does not affect this claim and can be eliminated.
C. in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as did younger individuals - If this were not true, it might explain why one age group would show more fractures. But choice (C) says that the two groups consumed carcasses equally thoroughly, so we don't have to worry about this possible age-related variable. Regardless, this doesn't have anything to do with the demographic bias referred to by the author. This bias only occurs if the fossils over represent certain age groups (i.e. older individuals). (C) can be eliminated.
D. the methods used to determine animals’ ages in fossil samples tend to misidentify many older individuals as younger individuals - The author claims that the fossils do not over represent older individuals. But what if the ages of the fossilized animals were not accurate? Choice (D) suggests that many of the "younger" fossilized animals may have actually been "older" individuals. In that case, the fossils WOULD over represent older individuals, and we'd have a demographic bias. Thus, choice (D) would undermine the researchers’ conclusion concerning the absence of demographic bias.
E. data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores - The author does not talk about using age data to determine behavioral differences. The author simply claims that the fossils do not over represent older individuals. Choice (E) is irrelevant.
gmatclubot
A recent study has provided clues to predator-prey dynamics in the lat [#permalink]