A-level生物学本身就是比较难懂的学科,因为它有大量的专业术语词汇需要记忆并且理解。在A-level考试中有这样的一类题,能让考生们难以下笔,它有着大量的生僻词汇,有着晦涩新颖的题型,它就是与传染疾病(infectious diseases)相关的题。让我们来看看A-level生物中关于传染疾病的叙述吧。
首先,A-level大纲中所涉及到的传染类疾病有四大疾病,最基本的你要清晰各个疾病的Pathogen(病原体,病原体的类型)和transmission way(传播途径)
Disease Name of Pathogen Type of Pathogen Transmission way
Cholera Vibrio cholerae bacteria Water-borne, food-borne
Malaria Plasmodium malariae Proctoctist Insect vector (female Anopheles mosquito)
Tuberculosis Mycobacterium tuberculosis Bacteria Air-borne
AIDS HIV Virus
sexual intercourses blood donation sharing needles
across placenta or through the breast milk
其次,根据不同疾病的特点,分析其在全球范围内的分布情况(global distribution)。endemic( diseases that are always in populations. For example: TB is endemic in the whole human population while malaria is endemic in tropical and sub-tropic.), epidemic ( there is asudden increase in the number of people with a disease.) and pandemic ( there is an increase in the number of cases throughout a continent or across the world.)。总的来说关于疾病的分布可以分成两大类:worldwide(全球)和endemic in some countries(部分国家):
1)全球分布的疾病有TB和AIDS,他们都有一个特征是他们都有long incubation period(长的潜伏期)加上贸易交流全球化,这就保证了infected people在不知道病情的情况下,带着病原体去到别的国家,将病原体传播出去。
2)局部分布:
cholera:contaminated water(被病原体污染的水)是cholera传播的关键环节,所以该疾病的传播主要区域即没有好的卫生条件(poor sanitation),无法进行有效污水处理(no sewage treatment)的贫困地区,例如Africa,Asia, Latin American。
malaria:female Anopheles mosquito是malaria传播的关键,它的生长繁殖需要一个温暖潮湿的环境(warm and moist),所以在热带(tropic)及亚热带(sub-tropic)特别盛行。
TB: TB虽然在全球范围内有,但是因为它是air-borne,所以在人口密集(large population)及没有好的住房保障(homeless)的区域特别突出。
梳理过后,你对于A-level生物学中的传染疾病有没有更加清晰的了解了呢?
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