6.13 Variation & Evolution

Differences in a population is called ‘variation’

  • each individual has different phenotypes (observable characteristics)

    • genes code for proteins

    • Genomes (all of your genes combined) code for an entire organism

  • Everyone (except identical twins) have different combinations of proteins, making everyone unique

  • Our phenotype also depends on our environment rather than just our genes

    • if identical twins have same gene for being tall, but one of them doesn’t eat / sleep enough, they will not be as tall

  • Most of our characteristics are determined by the interaction of our genes and our environment

Mutations

  • change in DNA code - protein that it codes for may be different

    • but most mutations don’t have an effect on proteins, so don’t change the organisms phenotype

    • In cases where protein coded for is changed, the phenotype may change slightly

      • this change is usually bad & unwanted

      • Occasionally the mutation is beneficial

  • Those with beneficial mutations are more likely to survive & pass on genes to next generation

    • ‘survival of the fittest’ noticed by Charles Darwin in the 1800s

      • noticed that certain traits were being passed from parent to child

      • And the most useful traits were passed on the most

  • ‘Natural selection’

    • fittest individuals being selected to survive

Evolution

  • inheritance of certain characteristics in a population, over multiple generations could lead to a change in the whole species

    • (sometimes even development of an entirely new species)

  • idea of evolution means that all living species must have evolved from simple life forms (first developed more than 3 billion years ago)

  • Took a long time for Darwin’s theory to become accepted

    • Proven many times by fossil records & antibiotic resistance in bacteria

  • evolution is the natural selection of genetic changes that give rise to the phenotypes that are best suited for the environment

    • given enough time, the phenotypes of 2 different populations within a species may become so different, they can no longer interbreed to produce fertile offspring

      • a new species has formed