Unit 1 · Introduction to Biology
What biology is, why life is hard to define, the three main branches of biology and the fields of study within them.
Biology is the science that gives special attention to the study of living organisms. The word comes from two Greek words: bios, meaning life, and logos, meaning study.
Nobody has managed to give a definition of life that every scientist accepts. Life is regarded as special and unique: the laws of chemistry and physics are needed to understand living things, but they cannot explain life completely on their own.
Biology is complex and covers a very wide area, so for convenience it is divided into three main branches:
Within each branch, living things can be studied from different angles. The main fields are:
| Field | What it studies |
|---|---|
| Cytology (cell biology) | cells |
| Histology | tissues |
| Anatomy | the gross (overall) structure of the body |
| Physiology | function |
| Biochemistry | biological molecules |
| Genetics | heredity |
| Ecology | the environment and how organisms relate to it |
A single piece of work often uses several fields together. For example, a study of how a bacterium causes a disease may need microbiology, biochemistry and physiology.
Exam tip: Learn the one-line meaning of each field in the table; matching a field to what it studies is a typical short question. Do not mix up histology (tissues) with anatomy (gross structure of the body).
Deshapriya Senevirathne. B.Sc. (Hons) Biology Special, University of Peradeniya — graduated with a class pass. All the content and lessons in A/L Biology on Paadama are reviewed by Deshapriya Senevirathne, and the lessons are taught by him.