Mass transport systems
Factors such as size or metabolic rate affect the requirements of organisms in terms of gas exchange. This has given rise to adaptations such as specialised exchange surfaces and transport systems.
In this topic, students need to understand mass transport in both animals and in plants. They need to demonstrate an understanding of the cardiovascular system in mammals, as an example of a mass transport system required due to size/metabolic requirements. Students will need to appreciate the gross structure of tissues and organs within those systems, and how this structure is related to function.
The role of haemoglobin and red blood cells in the mass transport system within mammals is a key concept for A level biologists to understand.
The volume and pressure changes during the cardiac cycle is a frequent question on exam papers, one which is often answered poorly. This topic gives rise to a range of data and could be a popular topic to ask context based mathematical questions on.
An understanding of the function of both xylem and phloem is a requirement of this topic. Students are often asked to interpret information from tracer and ringing experiments and relate this to the mass flow hypothesis.
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 other 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.
Links and Resources
This is a three page summary sheet on the cardiovascular system. The resource provides details of the functions and key mechanisms involved in the cardiovascular system. It explains the role of the cardiovascular system in homeostasis and describes atherosclerosis and the role of aspirin in managing heart attacks.
It is a clear concise summary with some good illustrations and the level is appropriate for A level.
There are some calculation based questions at the bottom of page three, which require students to work out cardiac output. These questions could be extended or linked to an exam question.
This is a three page summary sheet on the respiratory system. The resource provides details of the functions and key mechanisms involved in the respiratory system. It explains the role of this system in homeostasis and provides examples of what can go wrong.
As with its sister resource on cardiovascular system (see above) this resource provides a clear and concise summary with some good illustrations.
The questions provided at the bottom of the final page are quite open ended research type questions.
One possible way to use these two resources (cardiovascular and respiratory), would be to give one half of the class the respiratory summary and ask them to work in pairs to come up with a similar cardiovascular summary. The other half of the class then does the opposite. The summary sheets produced by each pair can then be compared to the resources. This would rely on them not cheating and looking at the other summary pages.
Alternatively students could look at these summary sheets and then be asked to produce something similar for transport in plants.
This article examines hypertension, living with high blood pressure, and the relationship between blood pressure and the kidneys.
Although originally intended for GCSE students, the article does provide a useful starter summary for A level students. It would be possible to use the article in class to go through the terminology and extra level of detail that needs to be included now that they are studying A level. For example the article uses the term furring up. At A level this will not be awarded marks, so students must use the term "atheroma" to describe the fatty deposits in arteries. Similarly high density lipoproteins and low density lipoproteins are the required terminology at A level.
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 A level students and will develop their skills in reading about an experimental procedure and looking at graphs/data produced.
Students could move on from reading this article to develop an understanding of partial pressure and how this is affects the oxygen dissociation curve.
It would be possible to use this Catalyst article and the one on blood pressure 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.
This is an interesting article for students to read, although it may not be directly related to specification requirements.
It does provide information on the structure of the gas exchange surfaces, which would be useful revision.
There are some terms used in the article, which students would need to be reminded are GCSE terms rather than A level ie water hating is not suitable at A level, but this is a good way to reinforce this requirement.
The article would be a useful homework or self directed study activity. Students could be asked to write a similar article on another lung disorder/disease, such as TB, pulmonary fibrosis, asthma or emphysema.
This video is a detailed and graphic account of the dissection of a pig’s heart. The dissection, and accompanying commentary, shows all of the main features of the heart. It should be shown after students have been made aware of the heart structure. The video can be the prelude for an actual dissection of a heart.
There are obviously a number of issues and sensitivities related to dissection. Teachers need to check A level specifications carefully as to the required practical activities at this level. It is always better wherever possible to for students to experience a dissection, even if they do not get their hands dirty themselves!
This five minute video is aimed at teachers to provide guidance on how to complete a successful pluck dissection, along with accompanying teacher’s notes.
The video focuses on the function of the breathing system, and a description is provided in the teachers' notes of how to inflate one of the lobes in the lungs via an incision made in the trachea.
It would be appropriate to show this video to A level students. This could be done with the sound turned off and the teacher providing a voice over which was aimed at students. In this way it would also be possible to include A level questions for the class to consider.
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 practicals 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 A level students would perform but this is a great practical to read through and answer the given questions on. Teachers could provide some results for students to interpret.
There are also practicals for which secondary data is provided. For example, the investigation on frog heart beat (page 45) is not an investigation that A level students would carry out, but the data presented in this booklet and the questions linked to this are a useful activity.
This is a short (three minute) video which explores how plants transport materials via the xylem and phloem. It is quite a simplistic video, but would work well as a quick starter activity to assess students prior knowledge and understanding of this topic from GCSE, before moving on to the level of detail that is required at A level.
This is a teacher reference resource on the subject of translocation in plants. It is an extremely detailed publication, probably above the requirement of A level standard. It would however make for valuable reading for any teachers wanting to confirm their own understanding of this topic before delivering it to students.
It would be possible to translate particular sections of the booklet into more student friendly language and make use of them. For example the section on the evidence for and against the mass flow hypothesis is particularly good.
This resource from SAPS supports the use of practicals across 2015 A level biology specifications.
This simple potometer allows students to work individually or in pairs to measure the rate of transpiration of a plant specimen within a one hour lesson. Assembled using low cost parts the apparatus offers an affordable potometer for all your students, giving them a chance to record water loss at regular intervals and an opportunity to investigate the effect of different abiotic factors on the rate of transpiration.
These resources and this practical allow students to develop their understanding of water transport through plants and factors that affect the rate of diffusion. Students can develop graph drawing skills, calculate rates of change, develop (and demonstrate) their skills of taking quantitative measurements as well as their ability to consider variables that need to be controlled.
Through the suggested questioning in the teacher support materials or the student worksheet students can be encouraged to explore the implications of their findings to real life situations.
- Tested materials to support the A-level practical endorsement (CPAC)
- Support materials for teachers and technicians
- Student worksheet to help provide evidence for meeting the practical skills requirements
- Student revision materials to help prepare for exams