theory of evolution (natural selection)

• Natural selection


  the process by which organisms with traits most favourable to their environment tend to survive with higher probability, produce more offspring and pass their favourable trait to their offspring
• biodiversity


  the variability among Earth's living organisms
• evolution


  the processes that have transformed life on Earth from its earliest forms to the vast diversity that characterises it
• microevolution


  small-scale variation of allele frequencies in the gene pool of a species
• macroevolution


  variation in allele frequencies at or above species level

  produces a whole new species rather than just small changes

  eg. the origin of mammals, the separation of aquatic and terrestrial animals, evolution of humans
• microevolution - gene flow


  the movement of alleles between populations due to the movement of individuals
• microevolution - genetic drift


  random events that cause a change in allele frequency
• microevolution - mutations


  changes in an organism's DNA that acts as a source of new alleles
• speciation


  the formation of new species
• convergent evolution


  the process by which organisms that are not closely related evolve similar structure in response to similar environmental conditions

  eg. dolphins and sharks - streamlined bodies, similar fins and tails
• divergent evolution


  the process by which one species branches out into different environments, producing organisms that possess different characteristics
• gradualism


  the theory that evolution is a continual, even and slow process of small changes over a long period of time, individuals possess small changes until they split into a number of different species
• punctuated equilibrium


  the theory that the evolution of species proceeds in a patten of long periods of stability (equilibrium/stasis) followed by rapid periods during which many new species emerge and some become extinct

  eg. the Cambrian Explosion shows all animal phyla evolving in 20 million years - rapid bursts of change after 540 billion years of no evolution