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The primary method previously used by paleontologists to estimate clim
[#permalink]
09 Aug 2021, 17:56
09 Aug 2021, 17:56
3
The primary method previously used by paleontologists to estimate climatic changes that occurred during Pleistocene glacial cycles was the determination of 18O/16O ratios in calcareous fossils. However, because this ratio is influenced by a number of factors, the absolute magnitude of the temperature difference between Pleistocene glacial and interglacial cycles could not be unequivocally ascertained. For example, both temperature fluctuations and isotopic changes in seawater affect the 18O/16O ratio. And, since both factors influence the ratio in the same direction, the contribution of each to the 18O/16O cannot be determined.
Fortunately, recent studies indicate that the racemization reaction of amino acids can be used to determine more accurately temperatures that occurred during Pleistocene glacial cycles. Only L-amino acids are usually found in the proteins of living organisms, but over long periods of geological time these acids undergo racemization, producing D-amino acids, which are not found in proteins. This reaction depends on both time and temperature; thus, if one variable is known, the reaction can be used to calculate the other..
Fortunately, recent studies indicate that the racemization reaction of amino acids can be used to determine more accurately temperatures that occurred during Pleistocene glacial cycles. Only L-amino acids are usually found in the proteins of living organisms, but over long periods of geological time these acids undergo racemization, producing D-amino acids, which are not found in proteins. This reaction depends on both time and temperature; thus, if one variable is known, the reaction can be used to calculate the other..
Question 1
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A
B
C
D
E
Question Stats:
50% (02:28) correct
50% (02:10) wrong based on 38 sessions
Show timer Statistics
Q1. It can be inferred from the passage that determination of the temperatures mentioned in line 17 through 18O/16O ratios and determination through racemization reactions both require which of the following?
(A) Calcium deposits known to be from Pleistocene seas
(B) Proteins containing both L-amino acids and D-amino acids
(C) Glacial debris from both before and after the Pleistocene period
(D) Fossil material from organisms living during the Pleistocene period
(E) Proteins containing both amino acids and 18O
Question 2
00:00
A
B
C
D
E
Question Stats:
65% (00:45) correct
35% (00:58) wrong based on 20 sessions
Show timer Statistics
Q2. The passage suggests that the 18O/16O ratio could be used more successfully as a means of measurement if scientists were able to
(A) determine the 18O/16O ratio in living animals as well as in fossil remains
(B) locate a greater number of calcareous fossils from the Pleistocene glacial and interglacial cycles
(C) locate the factors other than temperature fluctuations and isotopic changes in seawater that affect the 18O/16O ratio
(D) arrive at more exact determinations of which amino acids are found in the proteins of living organisms
(E) isolate the relative effects of temperature fluctuations and isotopic changes in seawater on 18O/16O ratios
Question 3
00:00
A
B
C
D
E
Question Stats:
77% (00:50) correct
23% (01:02) wrong based on 13 sessions
Show timer Statistics
Q3. The information in the passage can be used to answer which of the following questions?
I. Do temperature variations and isotopic changes in seawater cause the 18O/16O ratio to shift in the same direction?
II. What are the methods used to determine the 18O/16O ratio?
III. Is the study of racemization reactions useful in estimating climatic changes that occurred during Pleistocene glacial cycles if only one of the two important variables is known?
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and III
Question 4
00:00
A
B
C
D
E
Question Stats:
92% (00:57) correct
8% (00:45) wrong based on 13 sessions
Show timer Statistics
Q4. According to the passage, before the recent experiments described in the passage were completed, scientists could
(A) determine temperatures only for Pleistocene seas
(B) determine temperatures that occurred during Pleistocene glacial cycles only by examining fossil remains
(C) measure changes in temperatures that occurred during Pleistocene glacial cycles with only questionable accuracy
(D) only partially identify factors tending to lower Pleistocene temperatures
(E) accurately determine temperatures only for land masses affected by glaciation
Re: The primary method previously used by paleontologists to estimate clim
[#permalink]
14 Aug 2021, 12:03
14 Aug 2021, 12:03
1
Expert Reply
Q1. It can be inferred from the passage that determination of the temperatures mentioned in line 17 through 18O/16O ratios and determination through racemization reactions both require which of the following?
we need to look into both paragraphs because question is asking about both 8O/16O ratios and racemization reactions
(A) Calcium deposits known to be from Pleistocene seas
Not mentioned.
(B) Proteins containing both L-amino acids and D-amino acids
more related to racemization reactions
(C) Glacial debris from both before and after the Pleistocene period
Debris may not contain the fossil or useful stuff.
(D) Fossil material from organisms living during the Pleistocene period
Both required fossil material.
(E) Proteins containing both amino acids and 18O
18O/16O ratios don't require it.
Answer D
Q2. The passage suggests that the 18O/16O ratio could be used more successfully as a means of measurement if scientists were able to
Look into the first paragraph, specifically temperature fluctuations and isotopic changes in seawater.
(A) determine the 18O/16O ratio in living animals as well as in fossil remains
how it will help
(B) locate a greater number of calcareous fossils from the Pleistocene glacial and interglacial cycles
not about the quantity.
(C) locate the factors other than temperature fluctuations and isotopic changes in seawater that affect the 18O/16O ratio
we know about different factors : "this ratio is influenced by a number of factors"
(D) arrive at more exact determinations of which amino acids are found in the proteins of living organisms
It will not help
(E) isolate the relative effects of temperature fluctuations and isotopic changes in seawater on 18O/16O ratios
It will help us to measure accurately.
Answer: E
Q3. The information in the passage can be used to answer which of the following questions?
More of a mapping question
I. Do temperature variations and isotopic changes in seawater cause the 18O/16O ratio to shift in the same direction?
Yes
II. What are the methods used to determine the 18O/16O ratio?
the method is not mentioned
III. Is the study of racemization reactions useful in estimating climatic changes that occurred during Pleistocene glacial cycles if only one of the two important variables is known?
Given in 2nd paragraph.
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and II
Answer: C
Q4. According to the passage, before the recent experiments described in the passage were completed, scientists could
Not able to measure the temperature difference accurately as given in the first paragraph.
(A) determine temperatures only for Pleistocene seas
We could measure for other seas.
(B) determine temperatures that occurred during Pleistocene glacial cycles only by examining fossil remains
There can be other methods.
(C) measure changes in temperatures that occurred during Pleistocene glacial cycles with only questionable accuracy
Exactly
(D) only partially identify factors tending to lower Pleistocene temperatures
Not given anywhere
(E) accurately determine temperatures only for land masses affected by glaciation
Only is the issue.
Answer: C
we need to look into both paragraphs because question is asking about both 8O/16O ratios and racemization reactions
(A) Calcium deposits known to be from Pleistocene seas
Not mentioned.
(B) Proteins containing both L-amino acids and D-amino acids
more related to racemization reactions
(C) Glacial debris from both before and after the Pleistocene period
Debris may not contain the fossil or useful stuff.
(D) Fossil material from organisms living during the Pleistocene period
Both required fossil material.
(E) Proteins containing both amino acids and 18O
18O/16O ratios don't require it.
Answer D
Q2. The passage suggests that the 18O/16O ratio could be used more successfully as a means of measurement if scientists were able to
Look into the first paragraph, specifically temperature fluctuations and isotopic changes in seawater.
(A) determine the 18O/16O ratio in living animals as well as in fossil remains
how it will help
(B) locate a greater number of calcareous fossils from the Pleistocene glacial and interglacial cycles
not about the quantity.
(C) locate the factors other than temperature fluctuations and isotopic changes in seawater that affect the 18O/16O ratio
we know about different factors : "this ratio is influenced by a number of factors"
(D) arrive at more exact determinations of which amino acids are found in the proteins of living organisms
It will not help
(E) isolate the relative effects of temperature fluctuations and isotopic changes in seawater on 18O/16O ratios
It will help us to measure accurately.
Answer: E
Q3. The information in the passage can be used to answer which of the following questions?
More of a mapping question
I. Do temperature variations and isotopic changes in seawater cause the 18O/16O ratio to shift in the same direction?
Yes
II. What are the methods used to determine the 18O/16O ratio?
the method is not mentioned
III. Is the study of racemization reactions useful in estimating climatic changes that occurred during Pleistocene glacial cycles if only one of the two important variables is known?
Given in 2nd paragraph.
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and II
Answer: C
Q4. According to the passage, before the recent experiments described in the passage were completed, scientists could
Not able to measure the temperature difference accurately as given in the first paragraph.
(A) determine temperatures only for Pleistocene seas
We could measure for other seas.
(B) determine temperatures that occurred during Pleistocene glacial cycles only by examining fossil remains
There can be other methods.
(C) measure changes in temperatures that occurred during Pleistocene glacial cycles with only questionable accuracy
Exactly
(D) only partially identify factors tending to lower Pleistocene temperatures
Not given anywhere
(E) accurately determine temperatures only for land masses affected by glaciation
Only is the issue.
Answer: C
gmatclubot
Re: The primary method previously used by paleontologists to estimate clim [#permalink]
14 Aug 2021, 12:03
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