What Evidence Supports Evolution? GCSE Biology
Learn what evidence supports evolution in AQA GCSE Biology: fossils, inherited characteristics and antibiotic resistance, with a clear natural selection example.
Fossils and antibiotic resistance in bacteria are key evidence for evolution. Scientists also know that inherited characteristics are passed from parents to offspring in genes, which helps explain how populations can change over generations. For AQA GCSE Biology, this answer assumes the separate-science qualification; these ideas apply at both Foundation and Higher tier.
Fossils show change over time
Fossils are the remains or preserved traces of organisms from millions of years ago, found in rocks. Comparing fossils with organisms alive today helps scientists see how living things have changed over long periods. The fossil record is incomplete, though: many early organisms had soft bodies that left few traces, and geological activity has destroyed some evidence.
For example, fossils found in older rock layers may have different features from related organisms found in younger layers. This pattern supports the idea that inherited characteristics in populations have changed over time. However, a fossil does not show every intermediate stage.
No single fossil proves evolution on its own. Scientists build the explanation by combining many fossils with genetic evidence and observable natural selection.
Antibiotic resistance shows evolution happening
Bacteria reproduce quickly. Mutations can produce new strains, some of which are resistant to an antibiotic. When that antibiotic is used, resistant bacteria are more likely to survive and reproduce. They pass on the genes for resistance, so the resistant strain becomes more common in the population. This is an example of natural selection: inherited characteristics that help organisms survive become more common over generations.
The important exam distinction is that the antibiotic does not make bacteria mutate so that they become resistant. Mutations produce variation; the antibiotic kills susceptible bacteria, leaving resistant ones more likely to reproduce.
Together, fossils provide evidence of change over long periods, while antibiotic resistance lets us observe a population changing as an inherited characteristic spreads.
