Physiology of Organisms

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Physiology of Organisms (or PoO, pronounced as ‘poo’, as the organisers insist on calling it) is a very fun subject. It looks at biological systems across the range of scales, from nutrition in bacteria and single-celled organisms, through insects and mammals, right up to 2,000 tonne sequoia trees. It also looks at biological systems from a range of angles: from biochemistry and medicine as you might expect, right through to physics when you look at how giraffes can drink without having a stroke. Lectures cover a lot of ground and many of the lecturers will give extra details not printed in their notes. It is a fascinating course, relevant to all of the biological subjects in the second year, and interesting to Phys NatScis looking to broaden their horizons. If you are interested in animal or plant documentaries, this subject might just be for you.

There is a bit of overlap with Biology of Cells, especially the cell signalling discussed in Easter term. These subjects complement each other nicely, with details from PoO augmenting Cells essays, and vice versa.

The lecture series titles are listed below:

  • Introduction to Physiology
  • Hormones, Homeostasis and Equilibria
  • The Nervous System
  • Muscle and Movement
  • Cardiovascular Physiology
  • Animal Nutrient Acquisition
  • Animal Respiration in Air and Water
  • Osmoregulation in Animals
  • Energy, Metabolism and Thermoregulation
  • Introduction to Plant Physiology
  • Light and Gas Exchange
  • Plant Water Relations
  • Plant Transport and Senses
  • Physiology of Microorganisms and Microbe-Plant Interactions
  • Comparative Physiology
  • Sensing the Environment


Supervisions mainly cover the lecture and practical content for each week. They generally involve conceptual learning and practicing data handling questions for practicals. Supervisors may also often set essays as practice and to revise that week’s topic. Sometimes you get given information on animals which isn’t covered in the lectures, which is very helpful for writing good essays!


Practicals are split between animal physiology and plant physiology. You will have an animal practical class every other week in Michaelmas and Lent terms, and a single animal practical in Easter. You will also have three plant practicals in Lent term. The practicals are generally quite relaxed, and the practical organiser (Dr Mason) thinks that these practicals should be about investigation, rather than following a set of instructions. There is a general guide but you are also allowed to investigate other things that interest you. There will be several animal physiology practicals where you need to design the experiment yourself, considering factors that lead to uncertainty in the data. The plant practicals are a little more formulaic and feel quite like Biology of Cells practicals.

Attendance at the practicals is not compulsory but material covered in the practicals (and not the lectures) will be examined in the practical theory paper. You are generally welcome to come on a different day to the one in your diary, if for some reason the original day is inconvenient. At the beginning of every practical there is an hour-long debrief session, in which Dr Mason will introduce the practical, and go through results from the previous week. If you miss a practical, definitely try to attend the debrief at the beginning of the next session. Lots of information about the practicals (including debrief sheets and extensions) is uploaded onto the Moodle site, so this should be your first consultation if anything from the practical is unclear.


Over the year, you will get a lot of practice writing these essays, and you will come to learn what makes a ‘good’ essay (structure, relevance, detail, diagrams). This is the most useful preparation for the exam – it may well be the case that one of the exam questions is the same as (or similar to) an essay you have already written. Other good preparation is reading your lecture/supervision notes, reading the textbooks for some extra details, and, in the weeks before the exams, perhaps writing a few essays under timed conditions. One good way to revise is to time and rewrite your essays several times until you can make your wording very precise and finish the essay on time. Your supervisor may or may not be willing to give you feedback on these. Even if they do not, this can still be a useful exercise to give you an idea about how much you can write in an hour, and whether or not writing a plan is a good idea for you. Try to write the essay closed book, then compare against your notes or the textbook to see if you have missed anything.

Only a few multiple choice and practical papers are available on Moodle, though there is an ample bank of past essay titles. For some reason, the practical papers uploaded on Moodle are usually short and not very difficult but in the actual exam, most people struggle to finish the practical exam on time. The best way to revise is just to read, re-read, re-read (repeat) the lecture notes.

The pre- and post-practical quizzes on Moodle are a good way to ensure you understand all of the material. It is not necessary to complete these over the course of the year (though it is good practice to), but they are a good revision resource. Also useful is looking over your practical notes/Moodle debrief sheets, and skimming through your lecture notes to make sure your grasp of the important concepts is solid.


There are two PoO exams: a practical theory exam, and a theory exam.

The theory exam is three hours long and split into two sections: a shorter multiple-choice paper and an essay section. The multiple-choice section contains 45 questions. You have an hour for this but if you work quickly, it may be possible to finish this section in under an hour. The content examined in the multiple-choice questions is covered in the lectures – no extra reading is required here. Some will need simple calculations, but most are just factual recall. Some of the questions are worded to trip you up: make sure you read them very carefully!

For the essay section of the theory paper, you will have to write two essays, from a pool of six. These six titles are split into two themes. In the first are questions relating either to plant OR animal physiology (though comparisons between the two will always get credit). In the second are ‘integrative’ questions, spanning plants and animals, and these require some sort of comparison between plant and animal physiology. You must pick at least one ‘comparative’ essay, and your second choice may either be another comparative essay or a plant/animal-specific one. Here in the essays you should try to incorporate any additional reading you have done, and anything relevant from your supervisions. You will have an hour for each essay, so it is worthwhile to spend a few minutes at the beginning considering the question. Some people find writing an essay outline helpful. This can be a good way to organise your thoughts and make sure that you include everything. Additionally, if you run out of time, the examiner will be able to see your intended essay structure, and may well give you credit for it.

The most important consideration running through your mind when you answer one of these questions is: ‘is what I am writing relevant to the question?’. It is perfectly possible to write a superb essay covering material related to the question, but if you do not actually answer the question, you will not get credit. That being said, a good stab at an answer, even if you do not manage to get all of the detail down, will usually be rewarded with a decent mark.

The practical theory exam is only an hour-and-a-half long, and so is reasonably time-pressured. A few questions are information-recall, but most ask you to apply the concepts you have covered in the practicals and lectures. There will be some calculation questions (e.g. finding membrane potentials, solute concentrations, sweat loss, etc), but most require a short length of writing.

Useful resources

  • Hill, R.W., Wyse, G.A. & Anderson, M. (2016) Animal Physiology, 4th ed. Sunderland: Sinauer Associates, Inc.
  • Hopkins, W.G. & Hüner, N.P. (2004) Introduction to Plant Physiology, 3rd ed. Hoboken: John Wiley & Sons, Inc.
  • Randall, D., Burggren, W. & French, K. (2002) Eckert Animal Physiology, 5th ed. New York: W.H. Freeman & Co.
  • Schmidt-Nielsen, K. (1997) Animal Physiology, 5th ed. Cambridge: Cambridge University Press.
  • Taiz, L., Zeiger, E., Møller, I.M. & Murphy, A. (2015) Plant Physiology and Development, 6th ed. Sunderland: Sinauer Associates, Inc.
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