Excretion is the manner in which waste is removed from our body.

Theory behind the hook

This hook makes links to students’ prior knowledge by using an everyday example of separating wastes in everyday life. In this way students will be able to relate to the topic being introduced.

How this hook works

This resource begins by introducing experiences that everyone is familiar with, such as sweating and urination and questioning on the rationale for these processes taking place in the human body. This incorporation of engaging images serves to stimulate students’ interest. It is explained that we all produce household waste and get rid of it. (At this point the resource could be paused and the teacher could question students on the consequences of waste piling up in our homes). It is then explained that our body also produces poisonous wastes and the removal of waste from our cells is necessary. The concept is further developed in stating that the removal of waste is similar to a filtering system in which we keep the “good stuff” and filter out the “bad stuff” by using examples such as filtering in the laboratory, panning (searching) for gold or filtering in the kitchen. The resource concludes by explaining that this process of getting rid of wastes from the body is known as excretion.

Questions & Answers

  • What organ excretes sweat?
  • What organs produce urine?
  • What are the constituents of sweat?
    Salt and water
  • What other organs are involved in excretion? What do they excrete?
    Lungs excrete carbon dioxide.

Cross Curricular Links

Links can be made to Junior Certificate Home Economics in which the excretory system is covered in the biology section.


Compare the percentage of carbon dioxide in inhaled vs. exhaled air in the human body using a data logger.