Genetic Variation and Evolution

• Mutations generate genetic variation in a population
• These genetic variations lead to different phenotypes in a population
• Populations evolve when some members of the population have greater reproductive success than other members of the population

Evidence of Evolution

• Evidence of evolution can be found in extant (living) and extinct species
• Molecular evidence compares DNA sequences and amino acid sequences in proteins from different organisms to provide evidence of evolution
• When comparing the DNA sequence of a gene that is shared by different organisms, the more recently the organisms share a common ancestor, the more similar their DNA sequences will be
• The GAPDH gene in humans and in chimpanzees is over 99% similar in sequence, but the similarity in the GAPDH gene in humans and in dogs is only about 91% similar, indicating that humans and chimpanzees share a more recent common ancestor than humans and dogs
• Molecular evidence is considered very strong evidence since environmental factors do not usually change an organism's DNA sequence
• Morphology which includes homologous structures that have common ancestry but different functions, also provide evidence of evolution
• The number and arrangement of bones in human hands, bat wings, and whale fins are very similar, indicating common ancestry and evidence of evolution
• Fossils from organisms that no longer live on Earth provide evidence of evolution
• Transitional fossils show intermediate states between ancestral and modern species
• Fossils can be dated by studying the age of the rock layers in which they are found or by using radioactive isotopes to date the fossils
• Vestigial structures are anatomical features in some organisms that no longer seem to have a purpose in the modern organism but may have had a function in an ancestral organism