Biology is the study of living things as a whole — their classification, evolution, genetics, ecology and structure. Physiology is one branch of it, concerned specifically with how living things function: how the heart pumps, how nerves signal, how the kidney filters. All physiology is biology; biology is far wider.
The core difference
- biology — the science of life in general.
- physiology — the branch dealing with function: the mechanisms by which organisms and their parts work.
The distinction inside biology that matters most is between structure and function:
- anatomy — what the parts are and where they sit
- physiology — what those parts do and how
Anatomy tells you the heart has four chambers; physiology tells you how the pressure and valves move blood through them.
The other main branches
- genetics — heredity and variation
- ecology — organisms in relation to each other and their environment
- evolutionary biology — how populations change over time
- microbiology — organisms too small to see
- biochemistry — the chemical processes within and relating to living things
Where the words come from
Both are Greek compounds. Biology is bios (life) plus -logia (study of). Physiology is physis (nature) plus the same ending — originally the study of nature broadly, narrowed over time to the functioning of living bodies.
Physiology outside medicine
The word is not confined to human bodies. Plant physiology covers photosynthesis and water transport; exercise physiology studies how the body responds to activity; pathophysiology is the study of function disturbed by disease.
Frequently asked questions
Is physiology part of biology?
Yes. Physiology is the branch of biology concerned with how living things function, alongside branches such as genetics, ecology and microbiology.
What is the difference between anatomy and physiology?
Anatomy is structure — what the parts are and where. Physiology is function — what those parts do and how they do it.
Does physiology only apply to humans?
No. Plant physiology, animal physiology and exercise physiology are all established fields.