Sponges attach to the ocean floor (must be true type cr)

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thephoenix: Legendary Member; Posts: 1560; Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members; Thanked: 137 times

by thephoenix » Fri Apr 30, 2010 10:00 pm

Sponges attach to the ocean floor, continually filtering seawater for food and ejecting water they have just filtered to avoid reingesting it. Tubular and vase-shaped sponges can eject filtered water without assistance from surrounding ocean currents and thus are adapted to slow-moving, quiet waters. Because of their shape, however, these sponges cannot live in strong currents, since strong currents would dislodge them. Both of these varieties of sponge were widespread during the late Jurassic period.
The statements above, if true, most strongly support which one of the following claims?
(A) Few tubular or vase-shaped sponges lived before the late Jurassic period.
(B) Tubular and vase-shaped sponges were more common during the late Jurassic period than in succeeding geological eras.
(C) During the late Jurassic period there were many areas of the ocean floor where currents were weak.
(D) All sponges that are neither tubular nor vase-shaped inhabit areas of the ocean floor where there are extremely strong currents.
(E) No types of sponge live in large colonies, since sponges do not flourish in areas where much of the water has been filtered by other sponges.

[spoiler]i am b/n C and D; pls help to decide[/spoiler]

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Source: Beat The GMAT — Critical Reasoning | Fri Apr 30, 2010 10:00 pm

beat_gmat_09: Master | Next Rank: 500 Posts; Posts: 437; Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member; Location: India; Thanked: 50 times; GMAT Score:580

by beat_gmat_09 » Fri Apr 30, 2010 10:39 pm

thephoenix wrote:Sponges attach to the ocean floor, continually filtering seawater for food and ejecting water they have just filtered to avoid reingesting it. Tubular and vase-shaped sponges can eject filtered water without assistance from surrounding ocean currents and thus are adapted to slow-moving, quiet waters. Because of their shape, however, these sponges cannot live in strong currents, since strong currents would dislodge them. Both of these varieties of sponge were widespread during the late Jurassic period.
The statements above, if true, most strongly support which one of the following claims?
(A) Few tubular or vase-shaped sponges lived before the late Jurassic period.
(B) Tubular and vase-shaped sponges were more common during the late Jurassic period than in succeeding geological eras.
(C) During the late Jurassic period there were many areas of the ocean floor where currents were weak.
(D) All sponges that are neither tubular nor vase-shaped inhabit areas of the ocean floor where there are extremely strong currents.
(E) No types of sponge live in large colonies, since sponges do not flourish in areas where much of the water has been filtered by other sponges.

[spoiler]i am b/n C and D; pls help to decide[/spoiler]

Because of their shape, however, these sponges cannot live in strong currents

conclusion is - sponges (Tubular and vase-shaped) thus are adapted to slow-moving, quiet waters
above premise strongly insists support to B

I think Premise about jurrasic period is just additional info.

Whats the OA?

paddle_sweep: Master | Next Rank: 500 Posts; Posts: 379; Joined: Wed Apr 07, 2010 12:53 am; Location: Chennai,India; Thanked: 3 times

by paddle_sweep » Fri Apr 30, 2010 10:42 pm

IMO it's C..

Pls post OA.

iamseer: Master | Next Rank: 500 Posts; Posts: 170; Joined: Wed Jun 10, 2009 5:59 am; Thanked: 13 times

by iamseer » Fri Apr 30, 2010 11:01 pm

thephoenix wrote:Sponges attach to the ocean floor, continually filtering seawater for food and ejecting water they have just filtered to avoid reingesting it. Tubular and vase-shaped sponges can eject filtered water without assistance from surrounding ocean currents and thus are adapted to slow-moving, quiet waters. Because of their shape, however, these sponges cannot live in strong currents, since strong currents would dislodge them. Both of these varieties of sponge were widespread during the late Jurassic period.
The statements above, if true, most strongly support which one of the following claims?
(A) Few tubular or vase-shaped sponges lived before the late Jurassic period.
(B) Tubular and vase-shaped sponges were more common during the late Jurassic period than in succeeding geological eras.
(C) During the late Jurassic period there were many areas of the ocean floor where currents were weak.
(D) All sponges that are neither tubular nor vase-shaped inhabit areas of the ocean floor where there are extremely strong currents.
(E) No types of sponge live in large colonies, since sponges do not flourish in areas where much of the water has been filtered by other sponges.

[spoiler]i am b/n C and D; pls help to decide[/spoiler]

IMO C

D - We have no information of sponges other than tubular and vase shaped. There could be other sponges requiring similar environment like these two.

A - we have no information
B - again no information
E - again no information

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Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Fri Apr 30, 2010 11:51 pm

i am b/n C and D; pls help to decide

The correct answer must be true while the four incorrect answers could be false.

The correct answer must be choice C. We know that tubular and vase-shaped sponges can only live in weak currents, and not in strong currents. We also know that these types of sponges were "widespread" during the late Jurassic peiord. Thus, during the late Jurassic period, there must have been many areas of the ocean floor where currents were weak. Otherwise, these types of sponges would not have been widespread (denial test).

Choice D could be false. We know that tubular and vase-shaped sponges could only live in weak currents. As iamseer points out, this doesn't mean that tubular and vase-shaped sponges were the ONLY kinds of sponges that lived in weak currents. Thus, it doesnt' have to be true that ALL sponges that are not tubular or vase-shaped lived in strong currents.

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Testluv: GMAT Instructor; Posts: 1302; Joined: Mon Oct 19, 2009 2:13 pmFollowed by: 164 members; Location: Toronto; Thanked: 539 times; GMAT Score:800

by Testluv » Sat May 01, 2010 12:14 am

Because of their shape, however, these sponges cannot live in strong currents

conclusion is - sponges (Tubular and vase-shaped) thus are adapted to slow-moving, quiet waters
above premise strongly insists support to B

I think Premise about jurrasic period is just additional info.

Whats the OA?

But did the passage establish that there wasn't an even greater number of areas of ocean floors with quiet waters after the late Jurassic period?...Nope. Thus, choice B could be false. In a "must be true" type question, the passage has to prove that an answer choice must be true. Because the passage never discussed eras that came after the late Jurassic period, choice B could easily be false.

Also, note that in an inference or "must be true" type of question, you have to treat the entire passage as true. Thus, you don't necessarily have to break the passage down into conclusion and premise; instead, you can simply treat it as a set of facts.

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kaushals: Senior | Next Rank: 100 Posts; Posts: 34; Joined: Sat Apr 24, 2010 12:31 am

by kaushals » Sat May 01, 2010 1:20 pm

IMO C

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