GCSE AQA Biology 1 Evolution

GCSE AQA Biology 1 Evolution

1. Evolution

   • The theory of evolution
     • More than 3 billion years ago, life on Earth began as simple organisms from which all the more complex organisms evolved.
   • Similarities/differences allow classification
     • 1) Plants make their own food and are fixed to the ground 2) Animals move about and can't make their own food 3) Microorganisms are different to plants & animals
   • Evolutionary and ecological relationships
     • Evolutionary
       • * Species wich similar characteristics - similar genes because they share common ancestor (closely related), often look alike and live in similar habitat * Genetically different species can look alike too * Evolutionary trees show common ancestors/ relationships between organisms (more recent, more closely related)
     • Ecological
       • * Organisms in same environment with similar characteristics - might be in competition * Differences between organisms in same environment can show predator-prey relationships

2. Natural Selection

   • Charles Darwin's idea
   • 1) Individuals within species show variation due to differences in genes
     • 2) Individuals with characteristics that make them better adapted to environment have better chance of survival - more likely to breed successfully
       • 3) Useful genes more likely to be passed on to next generation

3. Mutations

   • Mutation: Change in organism's DNA
   • Mostly, mutations have no effect but can be beneficial i.e. produce useful characteristic
     • Beneficial mutation more likely to be passed on by natural selection
       • Over time, beneficial mutation will accumulate in a population

4. Darwin's idea was very controversial at the time...

   • Wasn't enough evidence to convince many scientists
     • Not many other studies had been done into how organisms change over time
   • No good explanation of how appeared or passed on - didn't know about genes/mutations
   • Went against religious beliefs - no need for God

5. Lamarck

   • Argued that if characteristic was used a lot it would become more developed in its lifetime
     • Believed acquired characteristics would be passed onto next generation

6. Evidence

   • Lamarck's hypothesis rejected - experiments didn't support
   • Discovery of genetics supported Darwin's idea
     • Provided explanation of how organisms born with beneficial characteristics can pass them on (via their genes)