Excretion

This is an engaging and informative lesson that looks at the meaning of excretion in detail and explores the functions of the organs involved with the excretion of carbon dioxide and urea. This lesson has been designed for students studying A-level Biology.

The lesson begins by introducing the definition of excretion to the students so that they are able to recognise that the substances being removed have to have come from a metabolic process in order to be excreted. This important difference to egestion (elimination) is a key detail which they need to understand at this level. Moving forwards, a quick competition is used to meet some of the organs that are involved in excretion. The remainder of the lesson focuses on the excretion of carbon dioxide. Links are made to the transport of carbon dioxide as hydrogen carbonate ions and how the affinity of haemoglobin for oxygen is affected when the carbon dioxide concentration is high. Students will meet the idea of deamination and the ornithine cycle and the key details of these two processes are covered. Progress checks have been written into this lesson at regular intervals, which challenge the students on knowledge from this lesson and prior knowledge, to enable them to constantly assess their understanding.