【请教】关于Lyme Disease的问题

晓野的野

Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these other species were increased, more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

A Whether populations of the other species on which deer tick larvae feed are found only in areas also inhabited by white-footed mice

B Whether the size of the deer tick population is currently limited by the availability of animals for the tick's larval stage to feed on

C Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice

D Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed

E Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans

答案是B

可是感觉很疑惑，原文说更多的幼虫会吃没有感染的hosts，所以tricks感染病毒的数量会减少。

这个好像和deer trick 的population的size没啥关系吧。
感觉D选项更加合适一点呢....

什么意思啊?
请各位NN过来指教一下~~

guaiss

我的理解是这样的
If the population of these other species were increased, more of the larvae would be feeding on uninfected hosts，so the number of ticks acquiring the bacterium would likely decline.
这句话的一个必要条件是 deer tick 的总量没有变多
总量 =  吃不带细菌的宿主的 + 吃带细菌的宿主的
如果deer tick的总量变多的的话 吃不带细菌的宿主的tick变多 吃带细菌的宿主的tick有可能也变多了 使得结论不成立
B选项描述了deer tick 总量有可能变多的一个因素

Yamm

分享我的简单思路：（类比成我们能理解的例子）
Lyme disease is caused by a bacterium transmitted to humans by deer ticks疟疾通过蚊子传播给人类。.  Generally deer ticks pick up the bacterium while in the larval stage from feeding on infected white-footed mice.  蚊子在幼虫时期喝臭水沟从而携带病菌。However, certain other species on which the larvae feed do not harbor the bacterium.  其他水沟没有病菌Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium―and hence the number of people contracting Lyme disease—would likely decline.如果没有病菌的水沟的数量增加了，那么这种携带病菌的蚊子的数量就下降。（暗含比例问题）
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文本分析：加强+if then
os：这个充分条件推出这个必要条件需要一个合理的解释。
命题重点在是否携带病菌的蚊子数量会下降。
------------------------
选项分析：
A 无关：携带病菌是否对蚊子有不良影响
B 无关：没有案例说人类的疟疾是他们喝臭水沟得的-与人类是否直接接触病原无关
C（ANS）：幼虫只进食一次，所以大概率上会吃到没有细菌的水沟-他们长大后就不会携带细菌。（取非削弱：幼虫有多次进食行为-幼虫早晚会吃到臭水沟）
D 无关:宿主是否能成为病菌的来源
E out of scope：与水沟是否携带其他病菌无关

SuriYang

感谢分享！               

kluivert

这道题说的是the number of...是绝对数量，不是相对数量（百分比）

B 现有的dear tick 的数量是否受 载体的多少 限制
不受限制， 那么意味着 载体多了 ，那 tick 数量也多了 ， 感染的tick数量应该也会多
受限制， 那意味着 载体变多了不会影响tick总数量， 那那些在不会让tick感染的新的载体的出现,就会起到分流作用，有效的降低tick感染的数量

举个简单例子
一个盛满水的3L的水杯... 往2 个 10L的 空水杯倒水
空水杯A ...干净
空水杯B .. 有点脏

所以在总水量确定的情况下， 往A倒的多，干净水就多；反过来往B倒的多就是脏水多...互相牵扯，你多我少，你少我多
如果水总量不限制了，水更多了，那脏水可以最多达到10L ...和干净水没一点关系

道理就是如此

Crystal0918

waihou32 发表于 2013-5-2 22:46
我的理解是如果deer tick的数量不会被available feed所限制,那么这些tick根本就不会在乎对食物的选择,也就 ...

同意！               

小灰灰养大鸟

Suppose ticks=100, mice=50, others=50 (which will increase to 60)
P(eat mice)=1/2 P(eat others)=1/2
N(infected)=50 N(infected)=50

If ticks are not hungry, the number of ticks won’t increase because more food are provided.
P(eat mice)=5/11 P(eat others)=6/11
N(infected)=45 N(infected)=55
The aim can be achieved.

However, if they are hungry, the number of them will increase with the increasing food.
P(eat mice)=5/11 P(eat others)=6/11
N(infected)=50 N(infected)=60
The aim cann’t be achieved.

Aiki-Shaw

我们固化逻辑是总量不会发生变化，所以要想到这个

Jez

钟无艳的威士忌 发表于 2016-10-24 15:09
想问一下如果dt的总量被其食物的可能性限制住了，那么当other species的数量增加以后，dt食物也增加了，那 ...

http://forum.chasedream.com/thread-572325-1-1.html 5楼，我曾经和你一样哈哈

wttlll

itssuperoli 发表于 2016-9-9 04:49
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pic ...

同意！               

钟无艳的威士忌

itssuperoli 发表于 2016-9-9 04:49
Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally, deer ticks pic ...

想问一下如果dt的总量被其食物的可能性限制住了，那么当other species的数量增加以后，dt食物也增加了，那么dt的数量也会增加，那么吃mice的dt数量就不会减少呀。我就是这点想不明白，求解答！