作者：北美考试院 托福写作组 叶建萍

本期考题考察的话题是常考话题，属于在托福综合写作考试中考察的生态类话题，主要考察动物的数量减少的原因。在TPO中涉及动物数量减少的话题有TPO 17, TPO 18, TPO23，TPO48。另外在近几年的考试中也出现了这类考题，比如（20170107CN）， （20170423CN），（20180331CN），（20180602CN）,（20180610CN）。

Keywords: reptile, homing behavior, survive 

20180610CN  阅读部分：

总观点：分析北美野牛数量下降是否是因为人类的活动。

1.  过去移民的美国人以bison为食，因为当地居民没有啥东西吃，bison又大又多；

2. 人们到了Bison的栖息地的时候还带了其他食草动物来，这些动物把草吃了Bison就没有东西吃了；

3.  Repeating gun的发明使得Bison更容易被加速它们数量减少。

听力反驳：

总观点：北美野牛数量的下降不是因为人类的活动。

1. 这些人是从美国东海岸往西海岸迁徙的，按理说应该从东部的开始吃，但事实上中西部地区的减少了，东部的没什么变化。该段落用虚拟语气反驳；

2. 这些物种所处的位置是高寒地带，它们的捕食者无法在那么寒冷的地方生存；

3. 其一，在repeating guns之前就已经有大量减少。其二，repeating guns的速度赶不上这个物种消失的速度。

TPO17  

阅读部分：

总观点：三个原因导致鸟类数量减少。

1. 人类居住地habitats的增加；

2. 农业用地的增加the growth of agriculture；

3. 杀虫剂chemical pesticides的使用。

听力反驳：

总论点：阅读部分的主张是站不住脚的

1. 人类的居住地habitats的扩张不会导致所有鸟类数量的下降，有的会增加；

2. 因为新品种作物的种植，农业用地会越来越少；

3. 新型杀虫剂的毒性变小，并且正在研制新型pest resistant crops，将来杀虫剂不会继续伤害鸟类。

题目解析：

1月4日的独立写作题重复了（20070113CN）考题。对于考生来说，这道题是很熟悉的话题，家庭作业，所以很容易想出相关的分论点。这道题，如果同意，每天做作业可以加深对知识的理解，培养好的学习习惯。相反，如果反对，学生可以培养兴趣爱好，身体健康和放松。所以考生可以根据自己喜好来确定立场，完成写作。

在分析题目时需要注意的是与反方观点对比一下，这样更有说服力。请参考如下范文：

Excellent academic performance is, undoubtedly, crucial for students to enter a decent university. For this purpose, some people suggest that students should be assigned homework everyday to acquire more knowledge and therefore get a higher grade. However, I disagree with this statement, for the sake of physical and mental health.

To begin with, school children will have a healthy mind by reducing their study pressure, if allowed to arrange their own lives freely after school. Since they already spend too much time, at least 8 hours, on attending classes in various subjects, including science, math, language, it will be extremely exhausted for them to continue their work after they leave school. On the other hand, without homework, they can enjoy their free time to develop their hobby and do their favorite things, like doing sports, seeing films or painting pictures, consequently, relieving academic stress and becoming psychologically healthy. My friend Jane, for instance, is in the top five in her class and under huge pressure, since it is a common phenomenon for her to stay at home doing assignment until 10 pm on the daily basis in order to review the lesson and get a higher grade. The consequence is that she begins to feel tired of study and suffers serious mental problems like insomnia, hair loss and depression. Conversely, if Jane were not required to accomplish homework per day, she would enjoy a healthy mind.       

Secondly, with more free time, they can work out regularly to build a strong body and therefore boost their immune system. To be more specific, most of students lead a sedentary life and face the risk of becoming ill, since they are supposed to sit in the classroom to read books and acquire academic knowledge during the daytime. In this case, regular exercise after school, even just half an hour, will give them an opportunity to relax their body or muscle, increase blood circulation and build up resistance to disease. In addition, physical exercise is able to protect their eyesight since spending too much time on studying will decrease kids’ eyesight, increasing the chance to become short-sighted and wearing glasses in the early age, which is detriment to their lives and future development.

From what has been discussed above, even though assigning everyday homework can improve the students’ academic performance, they will become healthy, physically and mentally, with more free time, which exert far-reaching influence on their lives.