Things that need to be interchanged between an organism and the environment

Surface area to volume ratio

Features of specialised exchange surfaces

Gas exchange in single-celled organisms

Features of terrestrial insects to reduce water loss

Gas-exchange system in insects

Use of diffusion in insects

Use of ventilation in insects

Spiracles in insects

Limitations of the insect gas exchange system

Countercurrent flow

Gas exchange in the leaf of a plant

Structure of a plant leaf

Adaptation of a leaf for gas exchange

Stomata

Why do large organisms need a transport system?

Features of transport systems

Transport system in mammals

Mammalian circulatory system

Types of blood vessles

Basic structure of blood vessles

Structure of arteries, veins and capillaries

Artery structure related to function

Arteriole structure related to function

Vein structure related to function

Capillary structure related to function

What is tissue fluid?

Formation and return of tissue fluid

How does tissue fluid form

Return of tissue fluid to the circulatory system via capillaries

Return of tissue fluid to the circulatory system via lymphatic system

Root of a dicotyledonous plant

Uptake of water by root hairs

The apoplastic pathway

The symplastic pathway

Symplastic pathway steps

The casparian strip

Active transport

Evidence for root pressure

Movement of water out through stomata

Movement of water across the cells of a leaf