GWD-6-11 好像没讨论过

华籍美人

Q9 to Q12:

      The sloth bear, an insect-eating

       animal native to Nepal, exhibits only one

       behavior that is truly distinct from that of

Line       other bear species:  the females carry

  (5)       their cubs (at least part-time) until the

cubs are about nine months old, even

though the cubs can walk on their own

at six months.  Cub-carrying also occurs

among some other myrmecophagous

(10)      (ant-eating) mammals; therefore, one

explanation is that cub-carrying is

necessitated by myrmecophagy, since

myrmecophagy entails a low metabolic

rate and high energy expenditure in

(15)      walking between food patches.  How-

ever, although polar bears’ locomotion

is similarly inefficient, polar bear cubs

walk along with their mother.  Further-

more, the daily movements of sloth

(20)      bears and American black bears—

       which are similar in size to sloth bears

       and have similar-sized home ranges—

reveal similar travel rates and distances,

suggesting that if black bear cubs are

(25)      able to keep up with their mother, so

too should sloth bear cubs.

      An alternative explanation is defense

from predation. Black bear cubs use

trees for defense, whereas brown bears

(30)      and polar bears, which regularly inhabit

treeless environments, rely on aggres-

sion to protect their cubs.  Like brown

       bears and polar bears (and unlike other

myrmecophagous mammals, which are

(35)     noted for their passivity), sloth bears

are easily provoked to aggression.

Sloth bears also have relatively large

canine teeth, which appear to be more

functional for fighting than for foraging.

(40)     Like brown bears and polar bears,

sloth bears may have evolved in an

environment with few trees.  They are

especially attracted to food-rich

grasslands; although few grasslands

(45)      persist today on the Indian subcontinent,

this type of habitat was once wide-

spread there.  Grasslands support

high densities of tigers, which fight and

sometimes kill sloth bears; sloth bears

(50)      also coexist with and have been killed

by tree-climbing leopards, and are often

confronted and chased by rhinoceroses

and elephants, which can topple trees.

Collectively these factors probably

(55)      selected against tree-climbing as a

defensive strategy for sloth bear cubs

Because sloth bears are smaller than

brown and polar bears and are under

greater threat from dangerous animals,

(60)      they may have adopted the extra pre-

caution of carrying their cubs.  Although

cub-carrying may also be adoptive for

myrmecophagous foraging, the behavior

of sloth bear cubs, which climb on their

(65)      mother’s back at the first sign of danger,

suggests that predation was a key

stimulus.

Q11:

Which of the following, if true, would most weaken the author’s argument in lines 18-26 (“Furthermore … sloth bear cubs”)?

              

1. Cub-carrying behavior has been observed in many non-myrmecophagous mammals.


2. Many of the largest myrmecophagous mammals do not typically exhibit cub-carrying behavior.


3. Some sloth bears have home ranges that are smaller in size than the average home ranges of black bears.


4. The locomotion of black bears is significantly more efficient than the locomotion of sloth bears.


5. The habitat of black bears consists of terrain that is significantly more varied than that of the habitat of sloth bears.

为什么这道题的答案不是C，而是D呢？locomotion 是说polar bear和sloth bear 的比较啊！而C在原文可以找到啊！

这道题没人讨论过，是不是太简单了，偶晕了，请指教！

[此贴子已经被作者于2005-5-26 16:06:18编辑过]

华籍美人

没人理？是不是太简单了，大家都懒得说啊，可我怎么就是想不通呢？

河西学校

原文说两者身体大小类似、活动范围和距离类似，因此黑熊可以自己走，小树懒也应该可以。

C 是support原来的结论了，如果C成立，home range(活动范围)更小的话，那小树懒就更应该可以自己走路了。

E:黑熊的栖息地地形比树懒的更具有多样化。

栖息地地形的比较。

因为原文讲的是为什么不能自己走，而要背。黑熊的栖息地多样化，未必说行走起来就很容易，也许都是不好走的路呢，那就是SUPPORT了。除非说黑熊栖息地比树懒的更容易行走，就是WEAKEN。（请NN指正）

D。The locomotion of black bears is significantly more efficient than the locomotion of sloth bears.

原文推理：身材、活动类似——>能力类似（能够自己走）。

D 比较的是某个能力成立的条件。他因削弱。

黑熊移动更有效率，那就是说单位时间内消耗的能量少，比树懒更有优势。因此黑熊能做到的，小树懒未必能够做到。 

Powellyao

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