Recap on Evolution

What is the Theory of Evolution? Evolution is defined as change over time. One of the earliest theories of evolution was put forward by Darwin. He studied physical differences in finches on the Galapagos Islands. From his studies he discovered the theory of Natural Selection which favors some adaptations. Organisms not favored can become extinct. Natural selection works off of competition for resources and adaptations that help animals survive in an environment.

Evidence for Evolution

Fossils (Palentology) The study of fossils Fossils show us what organisms looked like a long time ago We know how old they are- –Relative dating: what layer of rock the fossil is found in

How are fossils evidence? If modern species looked exactly the same as fossils, then it would show that nothing has changed but they do not look the same. Extinctions: species were not “fit” for the environment any more

Comparative anatomy Anatomy is the study of the body parts of an organism Homologous structures: structures in different species that are similar but have evolved to be different because they are used differently Vestigial structures: structures that no longer serve a purpose in modern organisms

Divergent evolution: when one species evolves into two or more –Adaptive radiation: when one species evolves into many Convergent evolution: when two unrelated organisms have similar structures because of their environment

How is anatomy evidence? If a group of organisms have similar structures, we know they had a common ancestor

Embryology Embryology is the study of embryos and how they are similar During the first few hours and days of development, all animals start out looking the same because they all use the same genes to get started.

How is embryology evidence? If the organisms are using the same genes to create the same structures, it shows that they were at one time the same organism and that they share a common ancestor

DNA and the universal code DNA is the genetic molecule for every organism on earth All organisms use A, T, G, and C which is called the universal code DNA makes proteins out of 20 amino acids Mutations cause changes to DNA sequences and amino acid sequences

How is DNA evidence? If all organisms use the same code (DNA), then they all started out as one organism (3.5 billion year ago) Mutations have caused changes to some organisms and other changes to other organisms The more similar the DNA (or protein) is between two species, the more recently they were related to each other

Population genetics Population genetics is a fusion of Darwin’s ideas with genetics Speciation is the creation of a new species Speciation can occur by: –Mutations –Gene flow –Genetic drift –Selective mating –Natural selection due to environmental changes

How is population genetics evidence? When speciation occurs, changes are made to the gene pool which cause different populations to be different If there are enough differences, they become isolated from each other and they are considered different species Types of isolation –Mechanical- Geographic –Seasonal- Behavioral –Habitat

Types of selection –Disruptive –Stabilizing –Directional