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Course structure

Roger lecturingAs a Cambridge Natural Sciences Tripos (NST) undergraduate, you will study three science subjects and a mathematics course in your first year (Part IA). In the second year (Part IB), you study three more science subjects, from a somewhat wider set of choices than in the first year. In your final year (Part II), you will focus on a single subject in depth, although there is usually the opportunity to choose modules within that subject.

Lectures and practicals

University teaching in NST IA Physiology of Organisms consists of three lectures each week, Tuesday, Thursday and Saturday at noon. In the Michaelmas term, there is one practical class every two weeks, from 12-1PM and then from 2-5PM on either Wednesdays or Fridays, while in the Lent term there is a practical class every week. There is only one practical class in the Easter term. In addition, you will usually have a one-hour Physiology of Organisms supervision each week, organised by your College.

Michaelmas Term

The first term of the Physiology of Organisms course begins with an overview of physiological ideas and problems, focussing initially on the properties of the cell membrane and the factors that contribute to the stability of the internal environment. We then turn to general topics of animal physiology – how the basic organ systems work, and how they respond to environmental challenges. Although mammalian physiology is taught in most detail, this is a comparative physiology course and so we also consider some of the different strategies found in other animals, such as fish and insects. For example, we discuss different mechanisms of gas exchange for animals living in air and water, how the cardiovascular system works in different organisms and how osmoregulation in a freshwater fish might differ from that of a desert mammal. The first term will also introduce you to the study of neurobiology, i.e. how nerve cells and sensory systems work: this can be taken as a second year subject in its own right.

Lent Term

Most of the second term is occupied with the study of the physiology of vascular plants, in which we see how plants interact with the environment to obtain raw materials and how these are processed and distributed within the plant. Control of growth and development is a major contributor to the spread and survival of plants at all stages of the life cycle, and we explore the functional links between changes in the world outside and the physiological responses that enable plants to counter or exploit them. The diversity of plants, adapted to varying environments in different parts of the planet, is underpinned by an extraordinary range of physiological strategies, and we examine the interplay of anatomy, biochemistry and molecular mechanisms at the heart of a selection of representative types.

Next, the physiology of micro-organisms is introduced. After the basic physiological strategies of bacterial and fungal growth are described, the course turns to a consideration of how such microbes might live on and inside plants. The mechanisms used by microbes to attack host plants and the defence responses of the host plant are then analysed. Finally the impact of infection on host plant physiology is assessed, as exemplified by the effects on crop yield and plant water relations.

Easter Term

In the third term you will learn about how animals regulate their body temperature and control their food intake to achieve energy balance. The course is rounded off with a set of lectures which look at how the size of organisms profoundly affects features such as metabolic rate, structure and locomotion. Having previously studied both animals and plants, the third-term lectures are more integrative, encouraging students to use what they know to examine similarities and differences between diverse organisms.


Experimental practical classes form an integral part of the Physiology of Organisms course, allowing you to explore for yourself what you hear about in lectures and to see how science is actually done. There are either one or two practical classes per week. In the first term, you will study the properties of membranes and of isolated nerves and muscles, measure action potentials and investigate how the organ systems are arranged in fish and mammals. In the second term you will examine the activity of your own heart, discover how different inhaled gas mixtures affect your breathing and measure the amount of sweat produced during different intensities of exercise. You will also examine the pharmacological effects of drugs on isolated intestinal muscle. The Plant Sciences practicals, also in the second term, explore how leaves control water loss and gas exchange, how enzymes are regulated and how plants respond to viral infection. In the third term, you will explore oxygen uptake by aquatic organisms of different sizes.


The examination in Physiology of Organisms takes place in early June, and from 2014-15 will consist of a written theory paper of three hours and a written practical examination of 1.5 hours.