Evidence for Evolution (AQA GCSE Combined Science: Trilogy): Revision Note

The theory of evolution by natural selection is now widely accepted and many sources of data are now available to support the theory of evolution

One very clear piece of evidence for evolution is antibiotic resistance in bacteria

An antibiotic is a chemical that can kill or inhibit the growth and reproduction of bacteria

Antibiotics are extremely useful to humans as some bacteria are pathogenic and can cause life-threatening disease

Bacteria reproduce, on average, every 20 minutes and therefore evolution occurs in a much shorter time span

Like all other organisms, within a population, there will be variation caused by mutations

A chance mutation might cause some bacteria to become resistant to an antibiotic (eg penicillin)

When the population is treated with this antibiotic, the resistant bacteria do not die

This means they can continue to reproduce with less competition from non-resistant bacteria, which are now dead

Therefore the genes for antibiotic resistance are passed on with a much greater frequency to the next generation

Over time the whole population of bacteria becomes antibiotic-resistant because the bacteria are best suited to their environment

Darwin’s theory of evolution by natural selection is now widely accepted

Evidence for Darwin’s theory is now available as it has been shown that characteristics are passed on to offspring in genes

Our understanding of genetics has made clear the mechanism by which natural selection can occur

There is further evidence for evolution in the fossil record and our knowledge of how resistance to antibiotics evolves in bacteria