GCSE Biology: Exchange and transport in animals
Having understood how substances are transported into and out of cells, GCSE Biology students need to be able to explain the need for exchange surfaces and transport systems in multi cellular organisms. Students need to be able to explain this in terms of surface area to volume ratio, and be able to calculate this ratio. Students need to describe some of the substances transported into and out of a range of organisms, in terms of the requirements of those organisms , this should include the transport of oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea.
Students commonly show confusion regarding surface area: volume ratio, as this is an important concept it is worth spending some time ensuring that students have fully grasped this concept and have the required maths skills to complete calculations. Active practical activities, such as those using agar jelly cubes are useful to develop understanding of this concept
Students find it particularly difficult to grasp how larger animals have a smaller surface area: volume ratio, so the use of a variety of teaching strategies including practical activites, modelling , and animations would be useful.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
ABPI interactive website *suitable for home teaching*
This page (page 2) of the abpi interactive resource on heart and circulation deals specifically with the need for a transport system, there is a diagram on surface area to volume ratio and a question at the end of the page, which students could answer and then compare with the correct answer provided. Ths could be used as a quick starter to a lesson to recap, or as aquick homework activity.
Oxygen Supply *suitable for home teaching*
This Catalyst article looks at how organisms get the oxygen they need from their surroundings and how it reaches cells. It also explores how oxygen transport is monitored, which is of vital importance in medical care.
The level of detail in this article is at a suitable level for GCSE Biology students and will develop their skills in reading about an experimental procedure and looking at graphs/data produced. This article could be used in class, with students working in pairs to produce a summary of the article, 5 key points or as a self study/homework activity to complete this task individually.
There are many ways to make effective use of Catalyst articles, a booklet has been produced which provides ideas on how Catalyst articles can be used with students and includes six exemplar activities. This booklet can be accessed at: https://www.stem.org.uk/elibrary/resource/27308>
Practical Guide 1: Gas Exchange and Transport in Plants and Animals
This resource is essentially a teacher/technician guide to a range of possible practical activities to investigate gas exchange and transport in both plants and animals. There are numerous practical’s within this booklet, some which could be used as they are written and some which may now need updating.
As well as the practical activities there is also the possibility of using the practical’s within this booklet as written tests of practical knowledge and understanding. For example the practical to investigate the extent to which the structures of blood vessels relate to the functions which they perform (page 49), might not be a practical which students would perform but this would be a good practical to read through and answer the given questions on. Teachers could provide some results for students to interpret.
Nuffield Biology Activities for GCSE
Although this is quite a dated publication there are a range of possible activities within it that could be used to support the teaching and learning of this topic. Activities B31, B32 and B33 (page 28 onwards-teachers notes) are practical/desk based activities, that could be used as self-study/homework activities
Studying Lung Surfactant
This is an interesting article for students to read, although it may not be directly related to the specification requirements. It does provide information on the structure of the gas exchange surfaces, which would be useful revision.
The article would be a useful homework or self directed study activity. It would be possible to use this Catalyst article and the one on respiratory system together. Half the class could be given one article to read and half the other article - students could then present a summary of the article to each other.
Effect of size on diffusion
In this relatively straightforward practical activity different sizes of agar jellu cubes are set up to see how far liquid penetrates them by diffusion over five minutes.
Students can then use the table provided to calculate surface area to volume ratio for different cubes of different sizes and then consider this against the time taken for the liquid to diffuse to the centre of the cube, which will allow them to calculate the rate of diffusion. As many students struggle with the calculation of surface area to volume ratio and the implications, it is worth taking some time to go through the calculations methodically.
There are various ways to amend this protocol and different options for set up--students can be provided with pre-prepared Agar cubes of the correct size (this does save a lot of time). Students could investigate using different shapes.
The downloadable student sheet for this practical includes some useful questions (remember to remove the second page-the answers!) before handing this out to students