Grade+9+2.1+Transport

=UNIT TWO: TRANSPORT IN LIVING SYSTEMS=

In the first week of unit two it will be necessary to provide the new Unit plan for this period. This has still to be finalised in parts so there may yet be some changes in the near future.

Water is the transport medium that allows substances to interact within our bodies and even our very cells. It has an impressive list of characteristics that make it an essential part of life as we know it. Watch the video below to gain an appreciation of water before we begin looking at the unit properly.

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The first set of concepts to be viewed will be some of the most fundamental relating to biology. They are known as Osmosis and Diffusion.


 * Diffusion:** The net movement of particles of a liquid or a gas from an area in which they are in high concentration to an area in which they are in low concentration.

The process is explained better by Moby and Tim at Mr.Hardy´s wikispace:

Moby and Tim explain Diffusion

McGraw Hill provide another version:

[|Diffusion by McGraw Hill]

Osmosis is actually just a special from of diffusion that relates to the movement of water through a semi-permeable membrane. There are two equally valid definitions:

OR
 * Osmosis:** The movement of water molecules from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane.
 * Osmosis:** The movement of free water molecules from an area in which they are in high concentration to an area in which they are in low concentration through a semi-permeable membrane.

An osmosis animation is provided below:

[|Osmosis]

and another video: media type="youtube" key="elixxVF4KDU" width="560" height="315"

Our next concepts are known as adhesion, cohesion and capillary transport. All of these rely on the polar nature of water and this is discussed in the video below:

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A good overall resource for investigating the polar nature of water is given below:

[|http://www.middleschoolchemistry.com/multimedia/chapter5/lesson1]

Here are the powerpoints of diffusion, osmosis and surface tension:



Here's the explaination of the coin practical with further explanations of surface tension, cohesion and adhesion: