Natural Selection
Individuals with helpful traits survive and reproduce more.
About this topic
Darwin and Wallace proposed natural selection as the mechanism of evolution: individuals in a population vary, some variations are heritable, more offspring are born than can survive, and those with advantageous traits are more likely to survive and reproduce, passing the traits on. Over generations, the proportion of helpful alleles increases.
Peppered moths during industrial pollution are a famous example. Selection acts on individuals, but populations evolve. It is not random, though mutation, the source of variation, is.
The peppered moth is a classic story: in industrial England, soot-darkened trees made dark moths better camouflaged against birds, so dark forms became common; after pollution fell, pale moths recovered. Selection acts on existing variation, and over generations the allele frequencies in the population change. Darwin was inspired by the finches and tortoises of the Galapagos, which differed between islands.
Fitness in biology means reproductive success, not strength. Natural selection has no goal or plan. A frequent misconception is that individuals evolve during their lifetime, such as giraffes stretching their necks; populations evolve, not individuals, and acquired traits are not inherited. Another is that it is random: mutation is random, but selection is not.
Key ideas
- Variation exists
- More offspring are born than survive
- Favourable traits spread
Quick check
Use cases: where Natural Selection helps
- Homework: review the key idea behind Natural Selection before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Natural Selection without notes.
- Visual learning: play with the interactive lab to see how Natural Selection changes when you adjust its inputs.
- Teaching a friend: explain Natural Selection in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Natural Selection?
Individuals with helpful traits survive and reproduce more.
What will I learn in Natural Selection?
Variation exists. More offspring are born than survive. Favourable traits spread.
Is Natural Selection part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Natural Selection lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Natural Selection?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.