Do Now What does it mean to evolve? Provide an example based on the modern theory of evolution.

Convergent Evolution Selective pressure Selective Pressure: any phenomena which alters the behavior and fitness of living organisms within a given environment. Converge- come together

Convergent Evolution The process that occurs when organisms that are not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

Similar traits independently evolve in unrelated species Analogous structures: same function, different structures Similar traits independently evolve in unrelated species

Bat wings and bird wings are analogous as flight structures: their structure and function have evolved by different routes from a flightless reptilian ancestor. Note for example that a good portion of the flight surface in bats consists of a membrane stretched between the extended digits (chiropatagium), whereas the digits of the bird are relatively small and do not support the flight surface.

Convergent Evolution leads to… Analogous structures: Body parts that are similar in structure and functions that have no anatomical or embryological similarities Ex. Bird wings and insect wings

Divergent Evolution When related species become more and more different in response to different environments Diverge: going apart Allopatric speciation

Divergent Evolution leads to… Homologous Structures: Body parts that are alike because of a common ancestor These structures may serve the same or different functions Ex. Forelimbs

Homologous structures Anatomically similar but different functions Same origin

Coevolution

Coevolution The change in the evolution of one species in response to a change in another species. Ex: Honeybees become dependent on flowers, and flowers become dependent on honeybees for survival.

Vestigial structures Organs that were useful for an ancestors, but no longer useful in the modern day species. Ex. Appendix Jean Baptiste Lamarck discovered and named vestigial structures