IGCSE生物知识点精讲——传染性疾病概念梳理（包括群体免疫概念）

本文将为大家精讲IGCSE生物知识点——Communicable diseases，我们会与你一起梳理这个TOPIC的所有重要概念，其中包括在今年引起了很多争议的群体免疫。

IGCSE生物考试简介

生物考试一共分为3张试卷: 选择卷(paper2)，简答卷(paper4) 和实验卷(paper5)。难度不会太夸张，但会涉及超多IGCSE生物知识点。

选择题Paper2-共40题， 每题1分，合计40分。Paper2的考试时长为45分钟。Paper2占最终成绩的30%。

简答题Paper4-共6个大题，每个大题大约包含5个小题，共计80分。Paper4 的考试时长为75分钟。Paper4 占最终成绩的50%。

实验题Paper5一共2个大题， 每个大题包含6- 12个小题，共计40分。Paper5 的考试时长为75分钟。Paper5 占最终成绩的20%。

IGCSE生物知识点精讲

Communicable diseases

What is a communicable disease?

A disease caused by a pathogen which can be passed between animals or plants eg. flu.

What is a pathogen?

A disease-causing microorganism e.g. bacteria

How do bacteria cause disease?

Once inside the body, they divide rapidly by binary fission. They kill cells and produce harmful toxins.

How do viruses cause disease?

They invade and reproduce inside living body cells, leading to cell damage.

Give three ways in which pathogens can be spread

By air - flu, tuberculosis and the common cold are spread by droplet infection.

By water - fungal spores in water spread plant diseases.

By direct contact - common in plant diseases and sexually transmitted infections.

Give four ways in which the spread of pathogens can be reduced

Hygiene - handwashing, disinfectants, tissues.

Reducing contact with infected individuals - quarantine.

Removing vectors - use of pesticides and insecticides, removal of habitats.

Vaccination.

Why is it especially important to prevent the spread of viral diseases?

Scientists have not yet developed cures for many viral diseases.

What is measles? 

Measles is a serious viral disease that can cause blindness and brain damage. The main symptoms are a fever and a red skin rash.

How is measles spread? 

By air - through the inhalation of droplets from coughs and sneezes.

What is HIV/AIDS? 

HIV is a virus which attacks and damages the immune system until it can no longer function properly. AIDS is the condition resulting from a long-term HIV infection. There is no cure or vaccine for HIV/AIDS.

What is herd immunity? (群体免疫）

If a sufficiently high proportion of a population are immune to a disease (especially through vaccination), the spread of this disease will be limited.

传染性疾病相关IGCSE生物知识点整理就到这里。 IG阶段对每个学员来说都至关重要，在IGCSE阶段，可以让学员体验不同国际课程，助力自己提前找到方向，因为从这时开始就是在为AL/IB选课及申请，做长线规划的准备。更不用提，许多英国大学都会将IGCSE成绩纳入录取标准了。所以IG阶段一定不能浪费，如果你还没有找到适合自己的IG学习方法，点击预约试听【橡沐IGCSE同步培训班】——

海归执教

对知识模块进行全面系统教学

根据不同考试局整理相关高频考察点

扫清学习过程中的各种障碍

针对不同问题点设置不同课程和教学方法

在有限的时间内

换来实打实的成效

英本申请热度近年来不断上升，让漂亮的IGCSE成绩单为你积累G5申请先发优势吧。

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