FreeScienceLessons · AQA BiologyEvolution by Natural Selection
Key facts
Natural selection — the four steps
1. Variation — there is genetic variation within a population (due to mutation)
2. Struggle to survive — individuals compete for food, space, mates
3. Survival of the fittest — individuals with advantageous characteristics are more likely to survive and reproduce
4. Inheritance — survivors pass on their advantageous alleles to offspring
Over many generations, the advantageous characteristic becomes more common
Antibiotic resistance — natural selection in action
Random mutation produces some bacteria resistant to an antibiotic
Antibiotic kills non-resistant bacteria
Resistant bacteria survive and reproduce
Resistance allele passed on to offspring
Resistant strain spreads through population
MRSA is a key example
Evidence for evolution — fill in the table
Evidence
What it shows
Fossil record
Genetics
Selective breeding
Darwin's finches
Exam questions — 3 questions · 8 marks total
⚡ This module includes extended questions (4–6 marks). These are where most marks are lost. Read the hint carefully. Write in linked sentences. The AI will identify exactly which mark scheme points you missed.
1 markNatural selectionAQA 8461 style
Which of the following best describes natural selection?
A Organisms change their characteristics during their lifetime to suit the environment
B Individuals with advantageous characteristics are more likely to survive, reproduce and pass on those characteristics
C All individuals in a population survive equally
D Only the largest individuals in a population survive
Explain how antibiotic resistance in bacteria develops through natural selection. (6 marks)
Hint: Cover all four steps of natural selection AND apply them specifically to antibiotic resistance. For Level 3 you must explain the genetics (mutation, alleles passed on) not just say "the resistant ones survive".
+60 XP
1 markEvidence for evolutionAQA 8461 style
Why is the fossil record considered incomplete evidence for evolution?
A Fossils can only form from large animals
B Fossils are found only in one location
C Most organisms do not fossilise — soft-bodied organisms rarely leave fossils, so many species are not represented