Evolution

Evolution

• The theory of evolution is that all of today's species have evolved from simple life forms that first started to develop over three billion years ago.
• Charles Darwin made an important theory about evolution. He used the observations he made on a huge world trip, along with experiments, discussions and new knowledge of fossils and geology, to suggest the theory of evolution by natural selection.
• Darwin knew that organisms in a species show wide variation in their characteristics (phenotypic variation). He also knew that organisms have to compete for limited resources in an ecosystem.
• Darwin concluded that the organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive. This idea is called the 'survival of the fittest'.
• The successful organisms that survive are more likely to reproduce and pass on the genes for the characteristics that made them successful to their offspring.
• The organisms that are less well adapted would be less likely to survive and reproduce, so they are less likely to pass on their genes to the next generation.
• Over time, beneficial characteristics became more common in the population and the species change- it evolves.
• Darwin's theory wasn't perfect. Because the relevant scientific knowledge wasn't available at the time, he couldn't give a good explanation for why new characteristics appeared or exactly how individual organisms passed on beneficial adaptations to their offspring.
• We now know that phenotype is controlled by genes. New phenotypic variations arise because of genetic variants produced by mutations. Beneficial variations are passed on to future generations in the genes that parents contribute to their offspring.
• Over a long period of time, the phenotype of organisms can change so much because of natural selectio that they form a completely new species. This is called speciation.
• Speciation happens when populations of the…