FreeScienceLessons · AQA BiologyEvidence for Evolution
Key facts
Evidence for evolution
Fossil record — shows how species have changed over time. Incomplete (many organisms did not fossilise) but consistent with gradual change.
Antibiotic resistance in bacteria — demonstrates natural selection happening in real time. Bacteria with resistance mutations survive antibiotic treatment and reproduce.
Similarities in DNA and protein sequences — closely related species have very similar DNA, suggesting common ancestry.
Comparative anatomy — similar bone structures in different species (e.g. pentadactyl limb in mammals).
Darwin vs Lamarck
Lamarck's theory: organisms change during their lifetime due to use/disuse and pass on these changes to offspring. E.g. giraffes stretched their necks and offspring were born with longer necks.
Why Lamarck was wrong: acquired characteristics are not inherited. Your DNA does not change because you go to the gym.
Darwin's theory: variation exists → natural selection → those best adapted survive → pass on alleles → gradual change over generations.
Darwin was reluctant to publish (contrary to religious beliefs). Alfred Russel Wallace independently developed similar ideas — Darwin published in 1859.
Exam questions — 3 questions · 11 marks
⚡ Extended questions included. Read the hint. Write in full sentences. AI marks against the AQA mark scheme.
1 markLamarck vs DarwinAQA 8461 style
How does Darwin's explanation of the giraffe's long neck differ from Lamarck's?
A Darwin argued giraffes with longer necks ate more food during their lifetime and this made their necks grow longer
B Darwin argued that there was variation in neck length; giraffes with longer necks could reach more food, survived better, and passed on alleles for longer necks to offspring
C Darwin argued that all giraffes evolved short necks and then all grew longer necks at the same time
Why is antibiotic resistance in bacteria considered evidence for evolution?
A It shows that bacteria can deliberately change their DNA to resist antibiotics
B It demonstrates natural selection occurring: resistant bacteria survive, reproduce and pass on resistance alleles, increasing the frequency of resistance in the population
C It proves that Lamarck's theory of acquired characteristics is correct
D It shows that antibiotics are becoming less potent over time
4 marksWhy the fossil record is incompleteAQA 8461 style
Explain why the fossil record does not give us complete evidence for evolution. (3 marks)
Hint: Cover: soft bodies don't preserve, specific conditions needed, fossils destroyed over time, rare process → gaps in the record.