求OG12-23（p.368）及逻辑简图

小尤

23.A明显是反了
     可是E是line37-38说的，但没有和close proximity of heart to head有关啊，它说的是arvoreal snakes.
希望大家给予解释。
我在看这篇文章的时候思路不清楚，如果有这篇文章的逻辑简图就更谢谢了。

timzf

In terrestrial environments, gravity places
special demands on the cardiovascular systems of
animals. Gravitational pressure can cause blood to
pool in the lower regions of the body, making it

(5)   difficult to circulate blood to critical organs such as
the brain. Terrestrial snakes, in particular, exhibit
adaptations that aid in circulating blood against the
force of gravity.
The problem confronting terrestrial snakes is best

(10) illustrated by what happens to sea snakes when

removed from their supportive medium. Because the
vertical pressure gradients within the blood vessels
are counteracted by similar pressure gradients in the
surrounding water, the distribution of blood

(15) throughout the body of sea snakes remains about
the same regardless of their orientation in space,
provided they remain in the ocean. When removed
from the water and tilted at various angles with the
head up, however, blood pressure at their midpoint

(20) drops significantly, and at brain level falls to zero.
That many terrestrial snakes in similar spatial
orientations do not experience this kind of circulatory
failure suggests that certain adaptations enable them
to regulate blood pressure more effectively in those

(25) orientations.

One such adaptation is the closer proximity of the
terrestrial snake's heart to its head, which helps to
ensure circulation to the brain, regardless of the
snake's orientation in space. The heart of sea snakes

(30) can be located near the middle of the body, a
position that minimizes the work entailed in
circulating blood to both extremities. In arboreal
snakes, however, which dwell in trees and often
assume a vertical posture, the average distance


(35) from the heart to the head can be as little as 15
percent of overall body length. Such a location
requires that blood circulated to the tail of the
snake travel a greater distance back to the heart,
a problem solved by another adaptation. When

(40) climbing, arboreal snakes often pause

momentarily to wiggle their bodies, causing waves
of muscle contraction that advance from the lower
torso to the head. By compressing the veins and
forcing blood forward, these contractions

(45) apparently improve the flow of venous blood
returning to the heart.

23. The author suggests that which of the following is a disadvantage that results from the location of a
snake's heart in close proximity to its head?

A. A decrease in the efficiency with which the snake
regulates the flow of blood to the brain
B. A decrease in the number of orientations in space that a snake can assume without loss of blood flow to the brain
C. A decrease in blood pressure at the snake's midpoint when it is tilted at various angles with its head up
D. An increase in the tendency of blood to pool at
the snake's head when the snake is tilted at various angles with its head down
E. An increase in the amount of effort required to distribute blood to and from the snake's tail

这题问的是心脏离头近有什么disadvantage。从line36~39可知心脏离头近将使得血液到达尾部更困难（因为循环距离长）。然后由line40~41可知为了解决这一困难，蛇需要间隙停下，然后wiggle(摆动)身体，这就是e选项中所指的An increase in the amount of effort

需要注意的是，虽然本篇阅读的一些问题都是问某一种蛇的，但本题的对象是a snake，并不是某一特定蛇种。

总体来说这是一篇比较难的科学文章，涉及不少专业词汇，而且更要命的某些生僻专业词汇对于解题是关键（比如arboreal，如果你知道这个词的意思，就会明白arboreal snake是terristrial snake的一种）

LEDGIRL

1段 。主题：讲terristrial snake如何通过自己器官（心血管系统）对环境（地球引力）的适应

2段。通过SEA SNAKE的例子来说明certain adaptations enable them
to regulate blood pressure more effectively in those
orientations.

3。具体分析这个ADAPTION 是什么                                                                 1）closer proximity of the
terrestrial snake's heart to its head, which helps to
ensure circulation to the brain, regardless of the
snake's orientation in space.

2）a vertical posture
3)  When

climbing, arboreal snakes often pause

momentarily to wiggle their bodies, causing waves
of muscle contraction that advance from the lower
torso to the head. By