Evidence for Evolution FOSSIL EVIDENCEProvides TRANSITIONAL LINKS Archaeopteryxlinks reptiles and birds Anatomical Evidence HOMOLOGOUS STRUCTURES ANALOGOUS STRUCTURES structures that are similar because they were inherited from a COMMON ANCESTOR similar in function, but NOT inherited from a common ancestor NOTE: similar structure, but NOT always function! NOTE: similar FUNCTION, but not STRUCTURE More Anatomical Evidence: Vestigial Structures Vestigial Structures are undeveloped structures that were functional in some ancestor, but are no longer needed in that organism. EMBRYOLOGYsuggests common ancestors BIOGEOGRAPHICAL EVIDENCE When we study the distribution of plants and animals on the planet, we notice: Animals evolved differently in each of the biogeographical regions We see evidence that as the continents drifted, organisms were separated and evolved. BIOCHEMICAL EVIDENCE Almost all living things use the same biochemical molecules DNA, Protein, ATP Vast diversity came about by only slight differences in the same genes The more closely “related” the organisms are, the more similar their DNA Patterns of Evolution Macroevolution refers to large-scale evolutionary patterns and processes that occur over long periods of time. Macroevolution Six important topics in macroevolution are: extinction adaptive radiation (divergent evolution) convergent evolution coevolution punctuated equilibrium changes in developmental genes Gradualism Punctuated Equilibrium Gradualism Organisms go through gradual and continuous change Punctuated Equilibrium Organisms go through fast periods of change, followed by long periods of no change (according to fossil record) Extinction More than 99% of all species that have ever lived are now extinct. Extinction Mass extinctions: provide ecological opportunities for organisms that survived result in bursts of evolution that produced many new species Patterns of Evolution: 1. Convergent Evolution Convergent Evolution: When 2 or more unrelated species become more similar due to similar adaptations to their environment. Patterns of Evolution: 2. Divergent Evolution-Adaptive Radiation Divergent Evolution: when related species become more different as they adapt to different environments Divergent evolution leads to Adaptive Radiation Coevolution Sometimes organisms that are closely connected to one another by ecological interactions evolve together. The process by which two species evolve in response to changes in each other over time is called coevolution. Adaptive Radiation of Mammals Ancestral Mammals This diagram shows part of the adaptive radiation of mammals, emphasizing current hypotheses about how a group of ancestral mammals diversified over millions of years into several related living orders. Note that the dotted lines and question marks in this diagram indicate a combination of gaps in the fossil record and uncertainties about the timing of evolutionary branching.