Topic 3: Organisms exchange substances with their environment (AQA A-level Biology)

This lesson bundle contains 17 detailed and fully-resourced lessons which cover the following specification points in topic 3 of the AQA A-level Biology specification:

Topic 3.1

• The relationship between the size of an organism or structure and its surface area to volume ratio
• The development of systems in larger organisms as adaptations that facilitate exchange as this ratio reduces

Topic 3.2

• Adaptations of gas exchange surfaces as shown by gas exchange in single-celled organisms, insects, bony fish and the leaves of dicotyledonous plants
• The gross structure of the human gas exchange system
• The essential features of the alveolar epithelium as a surface over which gas exchange takes place
• The mechanism of breathing to include the role of the diaphragm and the intercostal muscles

Topic 3.3

• During digestion, large molecules are hydrolysed to smaller molecules
• Digestion in mammals by amylases, disaccharidases, lipase, endopeptidases, exopeptidases and dipeptidases
• Mechanisms for the absorption of the products of digestion by cells lining the ileum of mammals

Topic 3.4.1

• The structure and role of haemoglobin in the loading, transport and unloading of oxygen
• The effects of carbon dioxide concentration on the dissociation of oxyhaemoglobin
• The general pattern of blood circulation in a mammal
• The gross structure of the human heart
• Pressure and volume changes and valve movements during the cardiac cycle
• The structure of the arteries, arterioles and veins
• The formation of tissue fluid and its return to the circulatory system

Topic 3.4.2

• Xylem as the tissue that transports water
• The cohesion-tension theory of water transport
• Phloem as the tissue that transports organic substances in plants
• The mass flow hypothesis for the mechanism of translocation in plants

If you would like to sample the quality of the lessons included in this bundle, then download the following lessons which have been uploaded for free

Alveolar epithelium
Absorption in the ileum
Arteries, arterioles and veins
Formation of tissue fluid
Translocation