Fiducia TogetherNatural selection and evolution
How populations change over generations. Four steps, in order.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Natural selection: there is variation in a population; some variants are better suited to the environment; those individuals are more likely to survive and reproduce; and they pass the advantageous alleles to their offspring, so the frequency of those alleles rises.
Where it applies
GCSE biology and combined science.
How it works
Variation arises from meiosis, fertilisation and mutation. Selection acts on it. Over many generations this can produce new species.
Antibiotic resistance is the standard modern example and the one most often asked about.
How to use it in your work
Write the four steps in order, every time. Marks are awarded per step.
Avoid saying organisms "want" or "try" to adapt, or that they change to suit the environment. Individuals do not adapt; populations change because some individuals reproduce more.
For antibiotic resistance, the resistant bacteria were already present by chance — the antibiotic selects, it does not create.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams. The subject song runs the topics in order.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Biology Song The GCSE biology specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.