Whale Origin

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Whale Origin

by Dean Jones » Sun Jan 08, 2012 12:41 pm
Dear Friends,

I was having problems in answering the following question.

Whales originated in the freshwater lakes and rivers of ancient Asia about sixty million years ago. Not until about ten million years later did species of whales develop specialized kidneys enabling them to drink salt water. Although fossil evidence shows that some early whale species that lacked such kidneys sometimes swam in the Earth's saltwater oceans, these species must have had to
return frequently to freshwater rivers to drink.
Which of the following is most strongly supported by the information given?

A. Fossils of whale species dating from between sixty million and fifty million years ago will not be found on continents that were at the time separated from ancient Asia by wide expanses of ocean.
B. Among whale fossils that date from later than about fifty million years ago, none are fossils of whale species that drank only fresh water.
C. Fossils of whale species that drank fresh water will not be found in close proximity to fossils of whale species that drank salt water.
D. The earliest whales that drank salt water differed from fresh-water-drinking whales only in their possession of specialized kidneys.
E. Between sixty million and fifty million years ago, the freshwater lakes and rivers in which whales originated were gradually invaded by salt water.



Please help.

OA after some discussions.

Regards
Deano.

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by bajjuri6 » Sun Jan 08, 2012 2:25 pm
I think A is the best option.

B == There is no text supporting this claim.

C == Since the whales moved back and forth between ocean-water and fresh-water, it's unlikely that the fossils couldn't be found at the intersection

D == This could a candidate answer. I can't come up with an idea to reject this.

E == Extreme claim

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by santhoshsram » Sun Jan 08, 2012 3:37 pm
Premises

1. Whales originated in freshwaters of ancient Asia around 60M years ago.
2. Specialized kidneys did not develop until 50M years ago.
3. Some fossils from 50 to 60 M years ago show whales without specialized kidneys swam in oceans.

Conclusion/Prediction: These whales must have frequently returned to freshwaters to drink.

I have my doubts if this is the conclusion, because most inference questions do not come with a conclusion. Yet this does not look like a premise to me.

Anyhow,

(A) The whales originated in asia + 50 to 60 M years ago did not have specialized kidney => Can't stay in saltwater for a long duration => So they would not have been able to swim across long stretches of ocean => Hence it is likely that they did not cross the ocean to reach another continent that was separated from Asia by wide expanses of ocean.

(B) We are told nothing about whale fossils less than 50 M years.

(C) Saltwater drinking whales could have lived close to the freshwater source where fresh water drinking whales also lived. That way fresh water drinking whales can swim to fresh water when needed. So C is not necessarily true. Maybe true, does not HAVE to be.

(D) We know saltwater drinking whales differed from fresh water drinking whales in that they had specialized kidney. But we have no idea if that is the only difference.

(E) We know nothing about what happened to the lakes and rivers.

IMO A
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by Joseph_Alexander » Fri Aug 01, 2014 1:31 am
A. Fossils of whale species dating from between sixty million and fifty million years ago will not be found on continents that were at the time separated from ancient Asia by wide expanses of ocean. OK - The conclusion must tie together two disparate claims: whales originated in Asia + species must have returned after swimming into salt water. This is the only conclusion that supports the authority of the claims. Take note of the "must"

B. Among whale fossils that date from later than about fifty million years ago, none are fossils of whale species that drank only fresh water. Reverse answer. This conclusion does not make sense after the premises given.

C. Fossils of whale species that drank fresh water will not be found in close proximity to fossils of whale species that drank salt water. Reverse answer. The fossils must be found in close proximity because "these species" must have had to return.

D. The earliest whales that drank salt water differed from fresh-water-drinking whales only in their possession of specialized kidneys. Could be true; shell game. It's tempting because indeed the kidneys must have been different. Even so, it need not be true. If it were true, it would need different support that what is provided.

E. Between sixty million and fifty million years ago, the freshwater lakes and rivers in which whales originated were gradually invaded by salt water. Could be true. If there freshwater lakes were not invaded by salt water, it is still possible that whale's kidney evolved because of a different cause.