Many theories have been formulated to explain the role of grazers

Question

6-2 SECTION A 20-27

Many theories have been formulated to explain the role of grazers such as zooplankton in controlling the amount of planktonic algae (phytoplankton) in lakes. The  first theories  of such grazer control were merely based on observations of negative correlations between algal and zooplankton numbers. A low number of algal cells in the presence of a high number of grazers suggested, but did not prove, that the grazers had removed most of the algae. The converse observation, of the absence of grazers in areas of high phytoplankton concentration, led Hardy to propose his principle of animal exclusion, which hypothesized that phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration. This was the first suggestion of algal defenses against grazing.

Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research. Increasingly, as in the individual studies of Lund, Round, and Reynolds, researchers began to stress the importance of environmental factors such as temperature, light, and water movements in controlling algal numbers. These environmental factors were amenable to field monitoring and to simulation in the laboratory. Grazing was believed to have some effect on algal numbers, especially after phytoplankton growth rates declined at the end of bloom periods, but grazing was considered a minor component of models that predicted algal population dynamics.

The potential magnitude of grazing pressure on freshwater phytoplankton has only recently been determined empirically. Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers. The high estimates of grazing pressure postulated by these researchers were not fully accepted, however, until the grazing rates of zooplankton were determined directly in the field, by means of new experimental techniques. Using a specially prepared feeding chamber, Haney was able to record zooplankton grazing rates in natural field conditions. In the periods of peak zooplankton abundance, that is, in the late spring and in the summer, Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production. Cladocerans had higher grazing rates than copepods, usually accounting for 80 percent of the community grazing rate. These rates varied seasonally, reaching the lowest point in the winter and early spring. Haney’s thorough research provides convincing field evidence that grazers can exert significant pressure on phytoplankton population.  
 1 
 1. The author most likely mentions Hardy’s principle of animal exclusion in order to

(A) give an example of one theory about the interaction of grazers and phytoplankton
(B) defend the first theory of algal defenses against grazing
(C) support the contention that phytoplankton numbers are controlled primarily by environmental factors
(D) demonstrate the superiority of laboratory studies of zooplankton feeding rates to other kinds of studies of such rates
(E) refute researchers who believed that low numbers of phytoplankton indicated the grazing effect of low numbers of zooplankton

2 
​ 2. It can be inferred from the passage that the “first theories” of grazer control mentioned ( Highlighted ) would have been more convincing if researchers had been able to

(A) observe high phytoplankton numbers under natural lake conditions
(B) discover negative correlations between algae and zooplankton numbers from their field research
(C) understand the central importance of environmental factors in controlling the growth rates of phytoplankton
(D) make verifiable correlations of cause and effect between zooplankton and phytoplankton numbers
(E) invent laboratory techniques that would have allowed them to bypass their field research concerning grazer control

3 
 3. ​​​Which of the following, if true, would call into question Hardy’s principle of animal exclusion?

(A) Zooplankton are not the only organisms that are affected by phytoplankton repellents.
(B) Zooplankton exclusion is unrelated to phytoplankton population density.
(C) Zooplankton population density is higher during some parts of the year than during others.
(D) Net phytoplankton are more likely to exclude zooplankton than are nannoplankton.
(E) Phytoplankton numbers can be strongly affected by environmental factors.

4 
 4. ​​​​​​The author would be likely to agree with which of the following statements regarding the pressure of grazers on phytoplankton numbers?

I. ​Grazing pressure can vary according to the individual type of zooplankton.
II.​ Grazing pressure can be lower in nutrient-poor lakes than in bog lakes.
III.​ Grazing tends to exert about the same pressure as does temperature.

(A) I only
(B) III only
(C) I and II only
(D) II and III only
(E) I, II, and III

5 
 5. ​​​The passage supplies information to indicate that Hargrave and Geen’s conclusion regarding the grazing pressure exerted by zooplankton on phytoplankton numbers was most similar to the conclusion regarding grazing pressure reached by which of the following researchers?

(A) Hardy
(B) Lund
(C) Round
(D) Reynolds
(E) Haney

6 
 6. ​​​​​​It can be inferred from the passage that one way in which many of the early researchers on grazer control could have improved their data would have been to

(A) emphasize the effects of temperature, rather than of light, on phytoplankton
(B) disregard nannoplankton in their analysis of phytoplankton numbers
(C) collect phytoplankton of all sizes before analyzing the extent of phytoplankton concentration
(D) recognize that phytoplankton other than net phytoplankton could be collected in a net
(E) understand the crucial significance of net phytoplankton in the diet of zooplankton

7 
 7. ​​​​​According to the passage, Hargrave and Geen did which of the following in their experiments?

(A) They compared the grazing rates of individual zooplankton species in the laboratory with the natural grazing rates of these species.
(B) The hypothesized about the population density of grazers in natural habitats by using data concerning the population density of grazers in the laboratory.
(C) They estimated the community grazing rates of zooplankton in the laboratory by using data concerning the natural community grazing rates of zooplankton.
(D) They estimated the natural community grazing rates of zooplankton by using data concerning the known population density of phytoplankton.
(E) They estimated the natural community grazing rates of zooplankton by using laboratory data concerning the grazing rates of individual zooplankton species.

8 
 8. ​​​​​Which of the following is a true statement about the zooplankton numbers and zooplankton grazing rates observed in Haney’s experiments?

(A) While zooplankton numbers began to decline in August, zooplankton grazing rates began to increase.
(B) Although zooplankton numbers were high in May, grazing rates did not become high until January.
(C) Both zooplankton numbers and grazing rates were higher in December than in November.
(D) Both zooplankton numbers and grazing rates were lower in March than in June.
(E) Both zooplankton numbers and grazing rates were highest in February.

mimishyu · Answer

para1: the main theme---the role of grazers(zooplankan) in controlling the amount of plantonic algae--- which form the three theories we will discuss about first theory: grazer control were merely based on observations of negative correlations between algal and zooplankton numbers. the absence of grazers in areas of high phytoplankton concentration -lead to --->Hardy’s principle of animal exclusion para2: flaw in para1’s study: consider only algae the size/deemphasize the role of grazers/grazing is just a minor component of models to predict alga population -->….second theory---researchers stress the importance of environmental factors(temperature、light、water) para3: use the idea of “grazing pressure” as third theory studies of Hargrave & Geen--- >estimate natural community grazing rate derive the estimates of grazing pressure -->Haney, record zooplankton grazing rates in natural field conditions by using different species& season to compare -->lead to the conclusion---“grazers can exert significant pressure on phytoplankton population” correspond to the pre-thinking summary: the author propose three kinds of theories, which he introduces one by one separately in para1-3, to explain the factors that will affect the role of grazers(zooplankton) in controlling the amount of planktonic algae 1. The author most likely mentions Hardy’s principle of animal exclusion in order to The converse observation, of the absence of grazers in areas of high phytoplankton concentration, led Hardy to propose his principle of animal exclusion, which hypothesized that phytoplankton produced a repellent(causing disgusting or able to repel) that excluded grazers from regions of high phytoplankton concentration. This was the first suggestion of algal defenses against grazing. (A) give an example of one theory about the interaction of grazers and phytoplankton ….correct Hardy's principle of animal exclusion ….which hypothesized that phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration. (B) defend the first theory of algal defenses against grazing though this can also function as the purpose of Hardy’s principle of animal exclusion, it( choice(A)) could only be the second, rather than to be the core, purpose of why the author mention Hardy’s theory (C) support the contention that phytoplankton numbers are controlled primarily by environmental factors ….this is second, not first theory, thus out of scope (D) demonstrate the superiority of laboratory studies of zooplankton feeding rates to other kinds of studies of such rates ….“feeding rates”, this is a term appear only in “third theory” , thus out of scope (E) refute researchers who believed that low numbers of phytoplankton indicated the grazing effect of low numbers of zooplankton ….nowhere in the passage has mention about whether there exist some “researchers believe low numbers of phytoplankton indicated the grazing effect of low numbers of zooplankton”, we only know from Hardy’s theory that “phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration” 2. It can be inferred from the passage that the “first theories” of grazer control mentioned (Highlighted) would have been more convincing if researchers had been able to (A) observe high phytoplankton numbers under natural lake conditions already practice by first theory, thus it won’t serve as a strengthener to the first theory (B) discover negative correlations between algae and zooplankton numbers from their field research already done by first theory, thus it won’t serve as a strengthener to the first theory (C) understand the central importance of environmental factors in controlling the growth rates of phytoplankton ….this is just a second theory function as offering another idea to the main theme, the three theories to which the author mentioned won’t conflict to each other by itself---this is a very important thing to know, thus even if this choice be true--whether it will strengthen or weaken Hardy’s theory we don’t know for sure (D) make verifiable correlations of cause and effect between zooplankton and phytoplankton numbers ….correct see sentences in para1&2 The first theories of such grazer control were merely based on observations of negative correlations between algal and zooplankton numbers. Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research. …..beside the negative correlation in first theory mention above, we should also consider “the role of grazers” ,which could also be a factor that affect algal and zooplankton numbers, to make the correlation more verifiable. (E) invent laboratory techniques that would have allowed them to bypass their field research concerning grazer control ….out of scope 3. Which of the following, if true, would call into question Hardy’s principle of animal exclusion? kind of weakening question type to trick you, I choose (E) at first but found it wrong (A) Zooplankton are not the only organisms that are affected by phytoplankton repellents. ….incorrect only this sentence in para1 mention about the repellents produced by phytoplankton: The converse observation, of the absence of grazers in areas of high phytoplankton concentration, led Hardy to propose his principle of animal exclusion, which hypothesized that phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration. ….nowhere in the passage mention about any organisms which would affected by phytoplankton repellents, thus the statement in this choice can’t constitute the weakener to Hardy’s principle (B) Zooplankton exclusion is unrelated to phytoplankton population density. ….correct If you doesn’t think thoroughly about the logic, its quite easy for you to get trapped, and the logic present as below: Hardy’s principle of animal exclusion/zooplankton exclusion -hypothesize that “phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration” regions of high phytoplankton concentration -this concern about the population density of phytolanton thus we know: if….. ……“zooplankton exclusion”—grazer repellent-- is related to ”population density of phytolanton”….. is true, -- then it could strengthen Hardy’s principle of animal exclusion and further… if….. ……“zooplankton exclusion”—grazer repellent-- is UNrelated to ”population density of phytolanton”….. is true, -- then it would weaken/put into question Hardy’s principle of animal exclusion (C) Zooplankton population density is higher during some parts of the year than during others. the problem to this choice is same as (A) see sentence in para3 below: Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers. (D) Net phytoplankton are more likely to exclude zooplankton than are nannoplankton. …not comparing which one, zooplankton or nannoplankton, are more likely to be excluded by net phytoplankton see sentence in para2: Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, (E) Phytoplankton numbers can be strongly affected by environmental factors. ….incorrect ….this is the main idea in second theory in para2, however, even if this choice be true, there still chances to which Hardy’s principle of animal exclusion won’t be called into question, this second theory isn’t within the same scope as the first one, that is—here ,we don’t know for sure 4. The author would be likely to agree with which of the following statements regarding the pressure of grazers on phytoplankton numbers? The potential magnitude of grazing pressure on freshwater phytoplankton has only recently been determined empirically. Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers. The high estimates of grazing pressure postulated by these researchers were not fully accepted, however, until the grazing rates of zooplankton were determined directly in the field , by means of new experimental techniques. Using a specially prepared feeding chamber, Haney was able to record zooplankton grazing rates in natural field conditions. In the periods of peak zooplankton abundance, that is, in the late spring and in the summer, Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production. Cladocerans had higher grazing rates than copepods, usually accounting for 80 percent of the community grazing rate. These rates varied seasonally, reaching the lowest point in the winter and early spring. Haney’s thorough research provides convincing field evidence that grazers can exert significant pressure on phytoplankton population. I. Grazing pressure can vary according to the individual type of zooplankton. Cladocerans had higher grazing rates than copepods, usually accounting for 80 percent of the community grazing rate ---> I establish II. Grazing pressure can be lower in nutrient-poor lakes than in bog lakes. The high estimates of grazing pressure postulated by these researchers were not fully accepted, however, until the grazing rates of zooplankton were determined directly in the field, by means of new experimental techniques.---->grazing pressure & grazing rates relate to each other Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production --->thus II can be established III. Grazing tends to exert about the same pressure as does temperature. temperature….second theory grazing pressure…third theory not relate to each other (A) I only (B) III only (C) I and II only....correct (D) II and III only (E) I, II, and III 5. The passage supplies information to indicate that Hargrave and Geen’s conclusion regarding the grazing pressure exerted by zooplankton on phytoplankton numbers was most similar to the conclusion regarding grazing pressure reached by which of the following researchers? (A) Hardy (B) Lund (C) Round (D) Reynolds (E) Haney...correct 6. It can be inferred from the passage that one way in which many of the early researchers on grazer control could have improved their data would have been to (A) emphasize the effects of temperature, rather than of light, on phytoplankton (B) disregard nannoplankton in their analysis of phytoplankton numbers ….opposite Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research. (C) collect phytoplankton of all sizes before analyzing the extent of phytoplankton concentration ....correct a practice that overlooked the smaller phytoplankton (nannoplankton)--->we should collect phytoplankton of all sizes (D) recognize that phytoplankton other than net phytoplankton could be collected in a net (E) understand the crucial significance of net phytoplankton in the diet of zooplankton 7. According to the passage, Hargrave and Geen did which of the following in their experiments? see sentences in para3: Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers. (A) They compared the grazing rates of individual zooplankton species in the laboratory with the natural grazing rates of these species. ….out of scope (B) The hypothesized about the population density of grazers in natural habitats by using data concerning the population density of grazers in the laboratory. ….out of scope (C) They estimated the community grazing rates of zooplankton in the laboratory by using data concerning the natural community grazing rates of zooplankton. ….incorrect ….not estimate the data by using data itself (D) They estimated the natural community grazing rates of zooplankton by using data concerning the known population density of phytoplankton. …incorrect the known population density of phytoplankton. ….is used for computing, not “measuring” the data (E) They estimated the natural community grazing rates of zooplankton by using laboratory data concerning the grazing rates of individual zooplankton species. …correct Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory 8. Which of the following is a true statement about the zooplankton numbers and zooplankton grazing rates observed in Haney’s experiments? Using a specially prepared feeding chamber, Haney was able to record zooplankton grazing rates in natural field conditions. In the periods of peak zooplankton abundance(zooplankton the highest), that is, in the late spring and in the summer, Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production. Cladocerans had higher grazing rates than copepods, usually accounting for 80 percent of the community grazing rate. These rates varied seasonally, reaching the lowest (grazing rates )point in the winter and early spring. Haney’s thorough research provides convincing field evidence that grazers can exert significant pressure on phytoplankton population. background knowledge need to know: winter 12-1-2 / spring 3-4-5 / summer 6-7-8 / fall 9-10-11 zooplankton numbers---highest----late spring 5 & summer 6-7-8 grazing rate---lowest---winter 12-1-2 & early spring 3 (A) While zooplankton numbers began to decline in August, zooplankton grazing rates began to increase. ….incorrect zooplankton grazing rates began to increase(in August) -----here we don’t know for sure (B) Although zooplankton numbers were high in May, grazing rates did not become high until January. ….incorrect grazing rates did not become high until January---false FEB & MARCH grazing rates still at the lowest point (C) Both zooplankton numbers and grazing rates were higher in December than in November. ….incorrect zooplankton numbers ….higher in December than in November grazing rates ….higher in December than in November-wrong, if reverse this statement to “grazing rates lower in Dec than in Nov” could establish (D) Both zooplankton numbers and grazing rates were lower in March than in June. ….correct, best match to the calculation below: zooplankton numbers---highest----late spring 5 & summer 6-7-8 March’s number

auradediligodo · Answer

Hi everyone,
Got 7/8 correct in 16:20 minutes, including 5:30 minutes to read.

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P1

In the first paragraph the author present the early theory about phitoplankton and grazers. Such theories were solely based on correlations and so they were not proved or disproved. Then the author proceeds by presenting Hardy's theory that suggested that algae could dented themselves by phytoplankton.

Purpose:   To present the first theories about grazers and phytoplankton along with Hardy's theory.

P2

In paragraph 2 the author mentions some factors that were neglected in the previous studies, factors such as the size of phytoplankton and variables such as lights and temperature that were found to be a part of the regulation of phytoplankton population dynamic.

Purpose:   to mentions factors that were previously neglected but significant in the understanding of the population dynamic.

P3

In the last paragraph the author presents two typologies of studies: laboratory study and in field study. The author claims that only the in field study can be reliable and the conclusion is that grazing affects significantly the population dynamics of phytoplankton.

Purpose:   To present two studies, laboratory and in field studies, and to claim that phytoplankton population dynamics are affected by grazing.

Main point

The main point of this passage is to preset different theories about the relation of phytoplankton and grazers and to claim that such relation is significant.

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1. The author most likely mentions Hardy’s principle of animal exclusion in order to

Pre-thinking

Function question

From paragraph 1:   This was the first suggestion of algal defenses against grazing.

(A)   give an example of one theory about the interaction of grazers and phytoplankton
(B) defend the first theory of algal defenses against grazing  no theory is defended 
(C) support the contention that phytoplankton numbers are controlled primarily by environmental factors  out of context  
(D) demonstrate the superiority of laboratory studies of zooplankton feeding rates to other kinds of studies of such rates  out of context 
(E) refute researchers who believed that low numbers of phytoplankton indicated the grazing effect of low numbers of zooplankton  the author does not want to refute any theory in P1

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2. It can be inferred from the passage that the “first theories” of grazer control mentioned (Highlighted) would have been more convincing if researchers had been able to

Pre-thinking

Inference question

From P2:   Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research

Had they considered the size of phytoplankton, per the author their studies would have been more significant

OR

From P1:   The first theories of such grazer control were merely based on observations of negative correlations between algal and zooplankton numbers. A low number of algal cells in the presence of a high number of grazers suggested,  but did not prove , that the grazers had removed most of the algae.

Such theories were just correlations but no cause.effect link was proved.

(A) observe high phytoplankton numbers under natural lake conditions  cannot be inferred 
(B) discover negative correlations between algae and zooplankton numbers from their field research  out of context 
(C) understand the central importance of environmental factors in controlling the growth rates of phytoplankton  out of context 
  (D)   make verifiable correlations of cause and effect between zooplankton and phytoplankton numbers  in line with pre-thinking 
(E) invent laboratory techniques that would have allowed them to bypass their field research concerning grazer control  out of scope

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3. ​​​Which of the following, if true, would call into question Hardy’s principle of animal exclusion?

Pre-thinking

Weaken question

Hardy's principal:  phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration.

Evidence used:  the absence of grazers in areas of high phytoplankton concentration,

(A) Zooplankton are not the only organisms that are affected by phytoplankton repellents. irrelevant 
  (B)   Zooplankton exclusion is unrelated to phytoplankton population density.  This option undermines the evidence used by Hardy to support his claim 
(C) Zooplankton population density is higher during some parts of the year than during others.  irrelevant 
(D) Net phytoplankton are more likely to exclude zooplankton than are nannoplankton.  irrelevant 
(E) Phytoplankton numbers can be strongly affected by environmental factors. irrelevant

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4. ​​​​​​The author would be likely to agree with which of the following statements regarding the pressure of grazers on phytoplankton numbers?

Pre-thinking

Inference question

I. ​Grazing pressure can vary according to the individual type of zooplankton.
 Can be inferred from the first lines of P2

II.​ Grazing pressure can be lower in nutrient-poor lakes than in bog lakes.
 Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production.

III.​ Grazing tends to exert about the same pressure as does temperature.
 Cannot be inferred

(A) I only
(B) III only
  (C)   I and II only
(D) II and III only
(E) I, II, and III

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5. ​​​The passage supplies information to indicate that Hargrave and Geen’s conclusion regarding the grazing pressure exerted by zooplankton on phytoplankton numbers was most similar to the conclusion regarding grazing pressure reached by which of the following researchers?

Pre-thinking

The high estimates of grazing pressure postulated by these researchers were not fully accepted, however, until the grazing rates of zooplankton were determined directly in the field, by means of new experimental techniques.  Later the author presents Haney in field studies that were in line with Hargrave and Geen’s conclusion

(A) Hardy
(B) Lund
(C) Round
(D) Reynolds
  (E)   Haney

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6. ​​​​​​It can be inferred from the passage that one way in which many of the early researchers on grazer control could have improved their data would have been to

Pre-thinking

Inference question

From P2:  Perhaps the fact that many of these first studies considered only algae of a size that could be collected in a net (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research.

(A) emphasize the effects of temperature, rather than of light, on phytoplankton
(B) disregard nannoplankton in their analysis of phytoplankton numbers
  (C)   collect phytoplankton of all sizes before analyzing the extent of phytoplankton concentration
(D) recognize that phytoplankton other than net phytoplankton  could be collected in a net 
(E) understand the crucial significance of net phytoplankton in the diet of zooplankton

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7. ​​​​​According to the passage, Hargrave and Geen did which of the following in their experiments?

Pre-thinking

Detail question

From P3:   Studies by Hargrave and Geen estimated  natural  community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers.

(A) They compared the grazing rates of individual zooplankton species in the laboratory with the natural grazing rates of these species.
(B) The hypothesized about the population density of grazers in natural habitats by using data concerning the population density of grazers in the laboratory.
(C) They estimated the community grazing rates of zooplankton in the laboratory by using data concerning the natural community grazing rates of zooplankton.
(D) They estimated the natural community grazing rates of zooplankton by using data concerning the known population density of phytoplankton.
  (E)   They estimated the natural community grazing rates of zooplankton by using laboratory data concerning the grazing rates of individual zooplankton species.

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8. ​​​​​Which of the following is a true statement about the zooplankton numbers and zooplankton grazing rates observed in Haney’s experiments?

Pre-thinking

Inference question

Let's evaluate the options

These rates varied seasonally, reaching the lowest point in the winter and early spring.

(A) While zooplankton numbers began to decline in August, zooplankton grazing rates began to increase.  opposite 
(B) Although zooplankton numbers were high in May, grazing rates did not become high until January.  incorrect  
(C) Both zooplankton numbers and grazing rates were higher in December than in November.  Opposite 
  (D)   Both zooplankton numbers and grazing rates were lower in March than in June.  correct. If the lowest point is in early spring, that is march, in June numbers must be greater 
(E) Both zooplankton numbers and grazing rates were highest in February.  cannot be inferred

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It's a great day to be alive!

arora1 · Answer

13.3 mins and all correct. Factual passage
Question 7 looked most tricky to me.. and i took almost 2 mins to decode it
 
Option D is wrong since it says " known population density of phytoplankton " whereas in the passage it is the  population density of grazers  (zooplankton )

PhantomAY · Answer

16m30s, 7 out of 8 correct.

Notes:

Paragraph1: many theories on roles of grazers before, but limited to only the negative correlation. Or the function of defense. 
Paragraph2: defects of those thoeries: overlooked smaller phytoplankton. Researchers start to emphasize environmental factors. Grazing was only considered minor. 
Paragraph3: some examples of recent study throw light back on the importance of grazing on population of pnytoplankton. "Convincing" evidence was provided

"but did not prove, that the grazers had removed most of the algae"  "This was the first suggestion of algal defenses against grazing."

so mentioning Hardy's principle of animal exclusion is just to provide an example of previous interpretations. A is the correct answer
B) "defend" is an opinion, which author did not provide
C) "environmental factors" is not mentioned until in later paragraphs
D) "superiority" is kind of ridiculous, not mentioned. Didn't see it in any of the correct answers (though this is not the reason to exclude it) 
E) "refute" is an opinion, which author did not provide

You can find hint from  "A low number of algal cells in the presence of a high number of grazers suggested,  but did not prove, that the grazers had removed most of the algae. " , which is the causality of the 2 elements in the relationship mentioned

A) could help, but not the biggest puzzle missing and explicitly mentioned by author
B) the negative correlation had been discovered already
C) same as A
D) BINGO, fits our pre-thinking
E) same as A

"...led Hardy to propose his principle of animal exclusion, which hypothesized that phytoplankton produced a repellent that excluded grazers from regions of high phytoplankton concentration. "  Hardy's principle is basically a hypothesis without any solid supporting evidence mentioned.

A) Don't care, and this confirms the repellent function. Strengthen not weaken
B) Break the logic link very brutally, very strong weaken answer
C) Doesn't matter, as long as in general the zooplankton population density is smaller when phytoplankton exists than when phytoplankton doesn't. The principle could still hold
D) so some phytoplankton works better than some, not weaken nor strengthen
E) this didn't touch how phytoplankton impact zooplankton, irrelevant

assuming grazing pressure manifest itself in grazing rate, as indicated by last paragraph

I: correct, refer to  "Cladocerans had higher grazing rates than copepods, usually accounting for 80 percent of the community grazing rate." 
II: correct, refer to  "Haney recorded maximum daily community grazing rates, for nutrient-poor lakes and bog lakes, respectively, of 6.6 percent and 114 percent of daily phytoplankton production." 
III: the comparison between grazing and temperature is not mentioned

Correct answer is C

Only Haney was mentioned in the last paragraph as a successor to utilize new techniques. E is the correct answer

Hardy was the first one to hypothesize the "defense" theory
Round, Reynolds and Lund are researchers who emphasizes the importance of environmental factors

Refer to  "Perhaps the fact that many of these first studies  considered only algae of a size that could be collected in a net  (net phytoplankton), a practice that overlooked the smaller phytoplankton (nannoplankton) that we now know grazers are most likely to feed on, led to a de-emphasis of the role of grazers in subsequent research."  author implies to include smaller phytoplankton would help improve the result

A) temperature is not mentioned until later
B) "disregard nannoplankton" was the issue highlighted by author, opposite answer
C) correct answer
D) recognition itself won't improve the data, you have to include data in the analysis
E) similar mistake as for C, understanding itself doesn't improve the data

Refer to  "Studies by Hargrave and Geen estimated natural community grazing rates by measuring feeding rates of individual zooplankton species in the laboratory and then computing community grazing rates for field conditions using the known population density of grazers." , which can be simplified to "grazing rate in lab" + "known population density in field" = "grazing rates in field"

A) they didn't know the "natural grazing rates", they used lab grazing rates to estimate it
B) they didn't "hypothesize" but "know" the population density
C) they didnt' estimate the "grazing rates in lab" but "grazing rates in field"
D) almost correct answer unless the last word "phytoplankton" change to "zooplankton"
E) correct asnwer

Very tricky detail and reference question, refer to below 2 parts:
   In the periods of peak zooplankton abundance, that is, in the late spring and in the summer  
  These rates varied seasonally, reaching the lowest point in the winter and early spring.

A) "grazing rates began to increase in August" contradicts "reaching lowest point in winter" 
B) "grazing rates did not become high until January" contradicts "reaching lowest point in early spring"
C) November and December both counts as winter, so we can't differentiate which one has higher number and rate
D) not sure- I didn't find the detail to confirm rate is higher in June (summer) than march (late spring). Additional info can be found on the "number side" which is at peak in late spring (March, Apr) and in summer (May, June, July). if the number reached peak in march, then very likely the rate is going down from there. Not info to deduce whether rate is higher in June than in March
E) we don't know about the rate other than "lowest in early spring and winter", can't tell which month has the highest rate value

Jks3000 · Answer

=> In the periods of peak zooplankton abundance, that is, in the  late spring  and in the  summer 
=> These rates varied seasonally, reaching the lowest point in the  winter  and  early spring.

Sajjad1994  For Q8, How would I know which month is Late Spring or which is Early Spring; Which is Summer?? (In Rajasthan,India we call month of march Summer) ?

Sajjad1994 · Answer

I suppose Rajasthan is a very warm area and if you call month of March the summer this will be an exception and a rare scenario. By the word "late" in late spring suggesting the passage is talking about March, on the other hand one thing which you should be sure of is Summer. If summer=June then Late spring ≈ March. Apart from this there is no black and white rule. Sometime we have to use our overall sense and feel about the writing.

Thank you

jiteshvij · Answer

Different hemispheres have different seasons, so the last question does not sound sensible.

mindsf · Answer

Totally agreed. The last question is showing how biased ETS was when giving this question
In my country:
Spring: Jan, Feb, Mar
Summer: Apr, May, June
Fall: July, August, Sep
Winter: Oct, Nov, Dec

Got 7/8 correct, except this one

mindsf · Answer

Your explanation for why D is wrong is crazily awesome. I tried to find a reason to eliminate D in my reviewing process, but did not have it until read your comment that. Beautiful analysis. Thank you.
 D) almost correct answer  unless the last word "phytoplankton" change to "zooplankton"

VerbalBot · Answer

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Many theories have been formulated to explain the role of grazers

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Many theories have been formulated to explain the role of grazers

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