Hi everyone,
Solved this one in 11:35 minutes, including 5:50 minutes to read.
--------------------------------------------------------------------------------P1In paragraph one we are presented with a puzzle: What causes an helix? Plus we are given a condition that affects some snails to be either dextral or sinistral, with the majority of snails that are dextral.
Purpose: The purpose of this paragraph is to highlight a puzzle: why is the majority of snails dextral?
P2In paragraph 2 we are given that if right and left handed snails were mirror images of one another, then the differentiation rate should not exist. BUT they are not that similar and there might be reasons for that. Maybe some disadvantageous conditions are responsible for this difference; Or maybe sinistral snails cannot mate with dextrals...
Purpose: The purpose of this paragraph is to highlight the possible explanations for the differentiation rate of sinistral and dextral snails.
P3Paragraph 3 outlines all the limits of the evolutionary mechanism in relation to why snails become dextral or sinistral. We are also given an example about some European snails: such snails are dextral or sinistral because of their mothers. But surprisingly, the incidence of dextral snails that have sinistral mothers is high.
Purpose: To state that the evolutionary mechanism cannot explain certain aspects of why sails are dextral or sinistral.
P4In paragraph 4 we are given another approach to the problem: the developmental approach. Such approach is used in studies about Psnails. In such sails handiness is determined during egg formation. But while we could change from sinistral to dextral through an injection, the opposite cannot occur. Hence the mystery is still there.
Purpose: The purpose is to consider another approach to explain the mystery of handedness in snails and to restate that the mystery remains unsolved
Main pointThe main point of the passage is to introduce the mystery of handedness in snails, consider some approaches to the problem and claim that the mystery remains unsolved.--------------------------------------------------------------------------------
1
Which of the following would serve as an example of “concomitant structural features” (line 13) that might disadvantage a snail of the rarer form?
Pre-thinking
Inference question
From P2: "But left- and right-handed snails are not actually true mirror images of one another.[b] Their shapes are noticeably different. Sinistral rarity might, then, be a consequence of possible disadvantages conferred by these other concomitant structural features."
I would say that we are on the lookout for a physical condition representing a disadvantage for the snail.
[/b]
A) shell and body that are an exact mirror image of a snail of the commoner form
Out of scope
B) A smaller population of the snails of the rarer form
Out of scope
C) A chip or fracture in the shell caused by an object falling on it
Out of scope
D) A pattern on the shell that better camouflages it
Out of scope
E) A smaller shell opening that restricts mobility and ingestion relative to that of a snail of the commoner form
In line with pre-thinking
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2
The second paragraph of the passage is primarily concerned with offering possible reasons why
Pre-thinking
Function question
Purpose: The purpose of this paragraph is to highlight the possible explanations for the differentiation rate of sinistral and dextral snails.
A) it is unlikely that evolutionary mechanisms could discriminate against sinistral snails
Never mentioned and cannot be inferred
B) sinistrality is relatively uncommon among snail species
The paragraph tries to explain why sinistrality is uncommon.
C) dextral and sinistral populations of a snail species tend to intermingle
opposite
D) a theory based on a developmental mechanism inadequately accounts for the predominance of dextrality across snail species
Cannot be inferred as the developmental theory is discussed in the last paragraph.
E) dextral snails breed more readily than sinistral snails, even within predominantly sinistral populations
cannot be inferred
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3
Which of the following accurately describes the relationship between the evolutionary and developmental theories discussed in the passage?
Pre-thinking
Inference question
"Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handedness."
A) Although the two theories reach the same conclusion, each is based on different assumptions.
No assumptions are mentioned
B) They present contradictory explanations of the same phenomenon.
No contradiction is presented
C) The second theory accounts for certain phenomena that the first cannot explain.
In line with pre-thinking
D) The second theory demonstrates why the first is valid only for very unusual, special cases.
out of scope
E) They are identical and interchangeable in that the second theory merely restates the first in less technical terms.
Cannot be inferred
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4
It can be inferred from the passage that a predominantly sinistral snail species might stay predominantly sinistral for each of the following reasons EXCEPT for
Pre-thinking
Detail question
Let's evaluate each single choice.
A) a developmental mechanism that affects the cell-division pattern of snails
Mentioned in last Paragraph
B) structural features that advantage dextral snails of the species
This is a reason for which dextral snails are predominant. Hence correct
C) a relatively small number of snails of the same hand for dextral snails of the species to mate with
Mentioned in P2
D) anatomical incompatibility that prevents mating between snails of opposing hands within the species
Mentioned in P2
E) geographic separation of sinistral and dextral populations
"Presumably an individual of the rarer form would have relative difficulty in finding a mate of the same hand, thus keeping the rare form rare or creating geographically separated right- and left-handed populations.". OUT
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