Theory of Evolution a change in inheritable traits

Theory of Evolution – a change in inheritable traits that occurs in a population over time Charles Darwin came up with 4 main ideas…. . 1) Individuals differ, and some of this variation can be inherited (adaptations) 2) Organisms produce more offspring than can survive, thus they must compete for resources, and only the most fit will survive and reproduce (survival of the fittest – Natural selection) 3) The most fit organisms pass on their heritable traits to their offspring 4) Species alive today are descended with modification from their ancestors (Descent with Modification)

Vocabulary of Evolution Adaptation – inherited traits that increase an organism’s chance of survival Fitness – ability to survive and reproduce in a given environment Natural selection – individuals best suited to their environment survive and reproduce most successfully • Driving force explaining evolution Common descent – all species come from a common ancestor

Evidence Supporting Evolution • Fossil record – comparing fossils from older to younger rock layers show changes over time and relationships between different organisms • Geographic distribution of living species – presence of similar looking but unrelated organisms in a similar environment caused by natural selection

Evidence Supporting Evolution • Embryological similarities – shows common descent in that all organism’s embryos begin looking the same for the first several weeks • Anatomical similarities Homologous structures – structures that have the same make-up or bone structure but different functions • Divergent evolution

Analogous structures – structures that have the same function but different make-up or structure • Convergent evolution Vestigial structures – structures that no longer have a purpose but no longer do but are still present in the organism

• Biochemical Similarities – the more closely related or identical the genetic code of two organisms, the more closely related they are • Observed speciation and human forced selective breeding Domestic breeds of dogs, horses, cats Polar bears from brown bears Antibiotic resistant bacteria; pesticide resistance