子机构
400-600-1123
logo 备考资讯 提分课程 公开课 答疑社区 申友FM
登录
注册
题库解析   >   现象解释型 题型   >  
本题由lindy提供
1405 次学习

The sloth bear, an insect-eating animal native to Nepal, exhibits only one behavior that is truly distinct from that of

other bear species: the females carry 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 (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 walkingbetween food patches. However, although polar bears’ locomotion is similarly inefficient, polar bear cubs walk along with their mother. Furthermore, the daily movements of slothbears 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 blackbear cubs are 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 and polar bears, which regularly inhabit treeless environments, rely onaggression to protect their cubs. Like brown bears and polar bears (and unlike other myrmecophagous mammals, which are noted for their passivity), sloth bears are easilyprovoked to aggression. Sloth bears also have relatively large canine teeth, which appear to be more functional for fighting than for foraging. Like brown bears and polar bears, slothbears may have evolved in an environment with few trees. They are especially attracted to food rich grasslands; although few types of grassland persist today on the Indiansubcontinent, this type of habitat was once widespread there. Grasslands support high densities of tigers, which fight and sometimes kill sloth bears; sloth bears also coexist withand have been killed by tree-climbing leopards, and are often confronted and chased by rhinoceroses and elephants, which can topple trees. Collectively these factors probablyselected 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 dangerousanimals, they may have adopted the extra precaution of carrying their cubs. Although cub carrying may also be adaptive for myrmecophagous foraging, the behavior of sloth bear cubs,which on their mother's back at the first sign of danger, suggests that predation was a key stimulus.

The author mentions rhinoceroses and elephants (see highlighted text) primarily

in order to

    A. explain why sloth bears are not successful foragers in grassland habitats
    B. identify the predators that have had the most influence on the behavior of sloth bears
    C. suggest a possible reason that sloth bear cubs do not use tree-climbing as a defense
    D. provide examples of predators that were once widespread across the Indian subcontinent
    E. defend the assertion that sloth bears are under greater threat from dangerous animals than are other bear species

登录申友GMAT,查看答案及解析

视频解析

暂无视频解析,点击获取更多视频内容

文字解析

答案:
C
第一结构:
The sloth bear... (1)Cub-carrying also occurs... (2)However, although polar... (3)Furthermore, the daily movements of sloth bears and American black bears... 第二结构:An alternative explanation is defense from predation. (1)Black bear cubs use trees... (2) Sloth bears also have relatively large canine... (3) Like brown bears and polar bears, sloth bears may have evolved in ... (4) Although cub-carrying may also be adoptive... The author mentions rhinoceroses and elephants (highlight) primarily in order to(一般细节题,第2结构第3层次) A. explain why sloth bears are not successful foragers in grassland habitats(层次未提及) B. identify the predators that have had the most influence on the behavior of sloth bears(绝对词) C. suggest a possible reason that sloth bear cubs do not use tree-climbing as a defense(rhinoceroses and elephants 是捕食sloth bears的一个例子,这些动物会撬树,所以对于本身栖息地树就不多,而且有那么多会撬树的捕食者在,躲树上捕食sloth bear的有效选择,所以带着幼崽走) D. provide examples of predators that were once widespread across the Indian subcontinent(与题目逻辑方向不符,题目问的是主要目的,这些动物存在与这个环境并不是主要目的,而是有这些存在,导致爬树上的保护措施对于sloth bear来说是没啥用的, 而且once windspread,现在也很多这些捕食者) E. defend the assertion that sloth bears are under greater threat from dangerous animals than are other bear species(无关比较)

GMAT会员

提交
OG视频
申友gmat小助手

添加官方小助手微信
了解更多GMAT考试与咨询

100蜜糖购买当前课程

当前蜜糖数:颗 去获取

立即购买 取消购买

吉祥物小蜜蜂

关注公众号

公众号

扫码关注申友GMAT公众号

立即获取12GGMAT核心资料

微信咨询

申友在线咨询二维码图片

扫码添加申友GMAT官方助手

立即咨询GMAT网课面授课程

联系申友 全国免费咨询热线:400-600-1123

Copyright © 2021 All Right Reserved 申友教育 版权所有 沪ICP备17005516号-3 免责声明 互联网经营许可证编号:沪B2-20210282