Natural Selection
- Biology
- Ages 11–14 · Grades 6–8
What you’ll find out
- Inherited variation, overproduction and competition lead to natural selection.
- Individuals with helpful inherited traits survive and reproduce more, so those traits become more common over generations.
- Selection happens today, as in antibiotic-resistant bacteria; it acts on existing variation and cannot create traits on demand.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
How natural selection works
Individuals of the same species vary, and some of those differences are inherited. In any environment, some variations help an individual survive and reproduce. Imagine a population of green and brown beetles living on brown soil. Birds easily spot and eat the green beetles, so more brown beetles survive to breed and pass on their colour. Over many generations, brown becomes more and more common. This process is called natural selection, and it was first explained by Charles Darwin and Alfred Russel Wallace.
Selection happening now
Natural selection is happening all around us, and bacteria show it clearly. Doctors use antibiotics to kill harmful bacteria, but occasionally a few bacteria carry a mutation that lets them survive the drug. Because bacteria reproduce extremely fast, those survivors can soon multiply into a large population that the antibiotic no longer affects. This is called antibiotic resistance, and it is a serious problem. It is one reason antibiotics should be used only when really needed and taken exactly as prescribed.
Curriculum links: NGSS MS-LS4-4 · NGSS MS-LS4-6 · England KS3: Genetics and evolution · Cambridge Lower Secondary Stages 7–9: Biology · NCERT Science, Classes 6–8