开学第一课爱德思生物学什么

如果你看到了这篇推文，很有可能你是“入坑”了。生物作为最难的国际课程之一，很多人都是避而远之的。

一来文字表述多，读题费时；二来，太多“主观性”的东西，答案不好把握；三来，难拿分，从每年的boundary就可以知道。

以October 2022 PDF Grade Boundaries为例，大概拿到50%原始分就可以a了。

但其实换句话来说，只要你够强，分分钟拿a*/A*，因为a*/A*原始分够低。

那么alevel生物到底学什么呢？根据爱德思考纲，这一节课你要掌握：

考点一：The importance of water

1.1、understand the importance of water as a solvent in transport, including its dipole nature

1.Dipole and Hydrogen bond

The separation of charge is called dipole

There polar covalent bond between Hydrogen and oxygen.

Water is a polar molecule and exhibit dipolarity--— it has a partial negative (δ–) charge on one side and a partial positive (δ+) charge on the other .

2.Properties of water(所有的“properties都来自于氢键”)

2.1 Water is a polar solvent.

Water can form hydrogen bonds with a variety of different substances(either polar or charged ionic compunds)

2.2 Water is an excellent transport medium

glucose

amino acid

sodium chloride

chloesterol

fat

oxygen

2.3 As water cools to 4 °C, it reaches its maximum density.

--This unusual property enables organisms to live in water, even in countries where it gets cold enough to freeze in winter

2.4 Water is slow to absorb and release heat – it has a high specific heat capacity.

High specific heat(高比热容)-- water can absorb or give off a great deal of energy without changing temperature a lot.

when water evaporates, large amount of heat energy are used to break hydrogen bonds and allow water molecule to seperate.

2.5 Water is a liquid – it cannot be compressed.

Water molecules are cohesive and adhesive

Cohesive--water attracting to each other by hydrogen bond.

Eg. surface tension; drinking draw; droplet

Adhesive--the attraction between water and other substance.

Eg. capillary action; meniscus; water climbs up paper towel or cloth

2.6 Water has a very high surface tension because the attraction between the water molecules

1.Mass Transport Systems

Single-celled organisms: glucose and oxygen can diffuse directly across the cell membrane because of the short distance

Multicellular organisms: diffusion across the outer membrane would be too slow because of the

large distance

The mass transport systems are used to carry raw materials from specialised exchange organs (e.g. the lungs and the digestive system) to the body cells, and to remove metabolic waste (e.g. carbon dioxide) Eg. circulatory system

资料来自《Edexcel International ALEVEL Biology EXAM GUIDE 》