lsat 4-7

Snazzy · 发表于 2003-12-20 00:45:00

7. Marine biologists have long thought that variation in the shell color of aquatic snails evolved as a protective camouflage against birds and other predators. Brown shells seem to be more frequent when the underlying seafloor is dark-colored and white shells more frequent when the underlying seafloor is light-colored. A new theory has been advanced, however, that claims that shell color is related to physiological stress associated with heat absorption. According to this theory, brown shells will be more prevalent in areas where the wave action of the sea is great and thus heat absorption from the Sun is minimized, whereas white shells will be more numerous in calmer waters where the snails will absorb more heat from the Sun’s rays.
Evidence that would strongly favor the new theory over the traditional theory would be the discovery of a large majority of
(A) dark-shelled snails in a calm inlet with a dark, rocky bottom and many predators
(B) dark-shelled snails in a calm inlet with a white, sandy bottom
(C) light-shelled snails in an inlet with much wave action and a dark, rocky bottom
(D) light-shelled snails in a calm inlet with a dark, rocky bottom and many predators
(E) light-shelled snails in a calm inlet with a white, sandy bottom and many predators

answer D. how can it be judged that the snails have dard and rocky ...? thanks

mindfree · 发表于 2003-12-20 02:59:00

If light shell in sandy area, it is for the old theory. New theory basically states that the color of shell is determined by the wave movement and heat, not color of the area. So D is for the new theory: light shell and dark bottom.

憧憬 · 发表于 2004-3-8 14:36:00

我不懂这道题，可不可以请大家解释一下，D是怎么推出来的？sandy bottom 和 rockybottom 以什么来判断，predators 是由stress推出来的吧

dansy · 发表于 2004-3-8 18:14:00

憧憬MM，这题涉及新旧两种理论。旧理论说海底贝壳类东东的颜色是它的保护色，如果海底深色，则它深色，如果海底浅色，则它也浅色，(这样可以躲避predator). 新理论则说，贝壳的颜色和吸热有关。如果大海波浪多，则吸热少，那么贝壳深色的多。如果大海平静，则吸热多，贝壳浅色多。答案D说浅色贝壳在一个平静，黑暗的海底，并且有很多predator. 如果按照旧理论，一个黑暗海底，又有很多predator, 那么采用保护色则贝壳类应为深色。但是这里是浅色，所以与旧理论矛盾。那么按照新理论，平静大海，贝壳就为浅色，正是D所说。其他答案均有和新理论矛盾之处。

憧憬 · 发表于 2004-3-8 20:22:00

谢谢JJ的解答，但是D选项中还有一个rocky bottom ，这个跟提干有什么关系阿

tangyi79 · 发表于 2004-3-10 16:53:00

大概是common knowledge吧

沙子一般都是浅色的，石头是深色的

snowjing · 发表于 2005-9-18 03:25:00

以下是引用mindfree在2003-12-20 2:59:00的发言：
If light shell in sandy area, it is for the old theory. New theory basically states that the color of shell is determined by the wave movement and heat, not color of the area. So D is for the new theory: light shell and dark bottom.

highlight部分是怎么得出来的？

文章旧理论说：white shells more frequent when the underlying seafloor is light-colored；

文章新理论说：white shells will be more numerous in calmer waters where the snails will absorb more heat from the Sun’s rays.

所以E错在哪里？sandy bottom不是可以absorb more heat from the Sun's rays.

???

lsat 4-7

lsat 4-7

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