Until recently, many biologists believed that invertebrate schools w

Question

Until recently, many biologists believed that
invertebrate “schools” were actually transient
assemblages, brought together by wind, currents,
waves, or common food sources. Jellyfish groupings,
  (5)   for example, cannot be described as schools—cohesive
social units whose members are evenly spaced and face
the same way. However, recent research has found
numerous cases in which crustaceans and other
invertebrates form schools as fish do. Schooling
  (10)   crustaceans such as krill regularly collect in such
massive numbers that they provide abundant food for
fish, seabirds, and whales.

Like schooling fish, invertebrates with sufficient
mobility to school will swim in positions that are
  (15)   consistent relative to fellow school members, and are
neither directly above nor directly below a neighbor.
The internal structure of such a school changes little
with external physical disruption but dramatically with
the advent of a predator.

(20)   Since schooling is an active behavior, researchers
assume that it must bring important benefits. True,
schooling would appear to make animals more visible
and attractive to predators. However, schooling leaves
vast tracts of empty water, thereby reducing a
  (25)   predator’s chances of picking up the school’s trail. A
large group maintains surveillance better than an
individual can, and may discourage predation by
appearing to be one massive animal. And although an
attacking predator may eat some of the invertebrates,
  (30)   any individual school member has a good probability
of escaping.

In addition to conferring passive advantages,
schooling permits the use of more active defense
mechanisms. When a predator is sighted, the school
  (35)   compacts, so that a predator’s senses may be unable
to resolve individuals, or so that the school can execute
escape maneuvers, such as freezing to foil predators
that hunt by detecting turbulence. If the predator
attacks, the school may split, or may employ “flash
  (40)   expansion”—an explosive acceleration of animals
away from the school’s center. When large predators
threaten the entire school, the school may attempt to
avoid detection altogether or to reduce the density of
the school at the point of attack; when small predators
  (45)   threaten the margins, school members may put on
dazzling and confusing displays of synchronized
swimming.

Schooling may also enable invertebrates to locate
food—when one group member finds food, other
  (50)   members observe its behavior and flock to the food
source. On the other hand, competition within the
school for food may be intense: some mysids circle
around to the back of the school in order to eat food
particles surreptitiously. Schooling can facilitate the
  (55)   search for mates, but as a school’s numbers rise, food
may become locally scarce and females may produce
smaller clutches of eggs, or adults may start to feed on
the young. Thus, circumstances apparently dictate the
optimal size of a school; if that size is exceeded, some
  (60)   of the animals will join another school.    1 
 1. Which one of the following best expresses the main idea of the passage?

(A) The optimal size of a school of invertebrates is determined by many different circumstances, but primarily by issues of competition.
(B) The internal structure of a group of invertebrates determines what defensive maneuvers that group can perform.
(C) Although in many respects invertebrate schools behave in the same way that fish schools do, in some respects the two types of schools differ.
(D) Certain invertebrates have been discovered to engage in schooling, a behavior that confers a number of benefits.
(E) Invertebrate schooling is more directed toward avoiding or reducing predation than toward finding food sources.

2 
 2. According to the passage, each of the following is characteristic of an invertebrate school EXCEPT:

(A) The number of members in a school is influenced by external circumstances.
(B) A school’s members are arranged directly above and below one another.
(C) A school’s members arrange themselves so that they all face in the same direction.
(D) The individual members of a school maintain regular spacing from member to member.
(E) Population increase in a school can diminish reproduction by individual school members.

3 
 3. If substituted for the word “resolve” in line 36, which one of the following words would convey the same meaning in the context of the passage?

(A) control
(B) answer
(C) reconcile
(D) distinguish
(E) pacify

4 
 4. Which one of the following best describes the final paragraph of the passage?

(A) Arguments for opposing points of view are presented and then reconciled.
(B) The disadvantages of certain types of choices are outlined and alternative choices are proposed.
(C) Two different interpretations of a phenomenon are evaluated and one is endorsed as the more plausible.
(D) The disadvantages of an action are enumerated and the validity of that action is called into question.
(E) Advantages and disadvantages of a behavior are discussed and some actions for avoiding the adverse consequences are mentioned.

5 
 5. According to the passage, jellyfish are an example of invertebrates that

(A) do not engage in schooling behavior
(B) form groups with evenly spaced members
(C) assemble together only to feed
(D) form schools only when circumstances are advantageous
(E) collect in such large numbers as to provide abundant food

6 
 6. It can be inferred from the passage that if cannibalism were occurring in a large school of crustaceans, an individual crustacean encountering the school would

(A) try to stay at the edge of the school in order to obtain food
(B) be more likely to be eaten if it were fully grown
(C) be unlikely to join that particular school
(D) try to follow at the back of the school in order to escape predators
(E) try to confuse school members by executing complex swimming maneuvers

7 
 7. Which one of the following, if true, would most clearly undermine the assumption about schooling mentioned in the first sentence of the third paragraph?

(A) Observation reveals that many groups of invertebrates are unable to execute any defensive maneuvers.
(B) Biologists find that some predators can always tell the difference between a school and a single large animal.
(C) Research demonstrates that the less an invertebrate associates with others of its species, the better its chances of survival.
(D) Biologists confirm that predators are more likely to notice a nearby school of invertebrates than to notice a single invertebrate.
(E) Researchers determine that the optimal school sizes for numerous species have each declined in previous years.

Its_me_aka_ak · Answer

I have doubts about question 7. Please assist.
Assumption: Researchers assume that it must bring important benefits.
Option A. suggests that the school of Invertebrates is unable to execute the defense, which means there is no benefit to being in a school, so does it not weaken the assumption enough? as it means that it would not bring the assumed benefits.

Sajjad1994 · Answer

Explanation

7. Which one of the following, if true, would most clearly undermine the assumption about schooling mentioned in the first sentence of the third paragraph?

Explanation

The  first sentence  of the  third paragraph  states,  "Since schooling is an active behavior, researchers assume that it must bring important benefits."  The question asks us to find the answer choice that would most clearly undermine this assumption about schooling. Let's analyze each option:

(A) Observation reveals that many groups of invertebrates are unable to execute any defensive maneuvers. 
This statement would weaken the assumption that schooling is an active behavior that brings important benefits because if many invertebrate groups cannot execute defensive maneuvers, it suggests that not all schools have the ability to actively defend themselves.

(B) Biologists find that some predators can always tell the difference between a school and a single large animal. 
This statement would not directly undermine the assumption in question. It is possible for some predators to differentiate between a school and a single large animal, but it doesn't necessarily negate the idea that schooling brings important benefits.

(C) Research demonstrates that the less an invertebrate associates with others of its species, the better its chances of survival.  
This statement directly contradicts the assumption in question. If research demonstrates that invertebrates survive better when they don't associate with others of their species, it challenges the idea that schooling (which involves associating with others) brings important benefits.

(D) Biologists confirm that predators are more likely to notice a nearby school of invertebrates than to notice a single invertebrate. 
This statement would not undermine the assumption because it doesn't address whether schooling brings important benefits or not. It merely states that predators may be more likely to notice a school, which is not directly relevant to the assumption.

(E) Researchers determine that the optimal school sizes for numerous species have each declined in previous years. 
This statement would not directly undermine the assumption. The decline in optimal school sizes for some species does not necessarily negate the idea that schooling brings important benefits.

The correct answer is  (C)  Research demonstrates that the less an invertebrate associates with others of its species, the better its chances of survival. This statement contradicts the assumption that schooling is an active behavior that brings important benefits, as it suggests that invertebrates may actually fare better when they avoid associating with others in schools.

Answer: C

Its_me_aka_ak · Answer

Thanks for the reply, but it is more like a general expansion.
My argument is as follows:
We need to  undermine  the assumption that  schooling has important benefits ( we gotta prove that it isn't effective).
Option B, for me, does that, as if they cannot execute the defense,  then schooling is of no use for sure.
 
Option D is saying that being alone is better for survival, which  does not imply that schooling is not beneficial .
If flavored water can better quench thirst, it does not mean that normal mineral water is not effective at all.

Sajjad1994 · Answer

(B)  is definite wrong, it only removes one benefit about animals schooling to appear like a big large animal, but it leaves all the other benefits.

nishantj1996 · Answer

Hey, the assumption that we are talking about here is that since schooling is an active behaviour, there must be 'important benefits' associated with it. Let's see what Option A says - Observation reveals that  many  groups of invertebrates are unable to execute any defensive maneuvers - the term many is extremely ambiguous - how many groups are we talking here? Furthermore, there still are other significant benefits to forming schools such as better surveillance , the ability to find food more easily, etc that make schooling a beneficial proposition. On the other hand, if you look at option D, it says that survival chances are much brighter if an individual invertebrates stays away from other members of its species, which means that all things taken into account, an individual invertebrate is much better off on its own, thereby suggesting that the 'net' benefit to it is negative (or in other words the costs outweigh the benefits). Hope this makes things clearer and if not, please give me a shout.

night2911 · Answer

could you help me on Q6? I'm thinking the "cannibalism" might be similar to a "predator"

GMATNinja · Answer

Question 6

The answer lies in the last couple sentences of the passage:

We can infer from this that cannibalism (adults feeding on the young) will occur if the optimal size is exceeded. In that case, some animals will break away from the school and join another.

If the school is so big that animals IN that school are leaving, we can infer that a newcomer would simply stay away. After all, why join if the group has already exceeded its optimal size?

So (C) is the best answer. I hope that helps!

Until recently, many biologists believed that invertebrate schools w

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Until recently, many biologists believed that invertebrate schools w

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