Evolution

Evolution

1. Theory of evolution: More than 3 billion years ago life on earth began as simple organisms from which all the more complex organisms evolved

2. All organisms are related even if only distantly

   • Evolutionary relationships
     • Species with similar characteristics often have similar genes because they share a recent common ancestor so they are closely related
     • Occasionally genetically different species might look alike to e.g. dolphins and sharks look alike because they live in the same habitat
     • Evolutionary trees show common ancestors and relationships between organisms
   • Ecological relationships
     • If we see organisms in the same environment with similar characteristics it suggests that they may be in competition
     • Differences between organisms in the same environment can show predator prey relationships

3. Natural selection explains how evolution occurs

   • Charles darwin
   • 1. individuals within a species show variation because of the differences in their genes
     • 2. Individuals with characteristics that make them better adapted to the environment have a better chance of survival and so are more likely to breed succesfully
       • 3. So the genes that are responsible for the useful characteristics are more likely to be passed on to the next generation

4. Evolution can occur due to mutations

   • 1. A mutation is a change in an organisms DNA
     • 2. Most of the time mutations have no effect but occasionally they can be beneficial by producing useful characteristics.
       • 3. If so the beneficial mutation is more likely to survive to be passed on to future generations by natural selection
         • 4. Over time the beneficial mutation will accumulate in a population

5. Not everyone agreed with Darwin

   • It went against all common religious beliefs about how life on earth developed it was the first plausible explanation for our own existence without the need for a god
   • Darwin couldnt give a good explanation for why these new useful characteristics appeared or exactly how individual organisms passed on their beneficial characteristics to their offspring
   • There wasnt enough evidence to convince many scientists because not many other studies had been done into how organisms change over time

6. Lamarck had different ideas

   • Lamarck argued that if a characteristic was used a lot by an organism then it would become more developed during its lifetime
   • Lamarck believed that these acquired characteristics would be passed on to the next generation