Evidence to Support Evolutionary Theory Fossils Similarity of embryos Homologous and analogous structures Vestigial structures Similarities in macromolecules http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

A) Fossils Most of the evidence for evolution comes from the fossil record Fossils show how much (or how little) organisms have changed over time One of the problems with the fossil record is that it contains gaps. Not all organisms fossilize well, and there will be many fossils that have been destroyed by the movements of the Earth, or simply not yet been discovered.

B) Embryos of all vertebrates are similar – indicating a common ancestor

C) Homologous Structures Develop from similar embryonic tissue May or may not have a similar function Suggest a common ancestor

C) Analogous Structures Structures in unrelated organisms that carry out the same functions Develop from different embryonic tissues Do not share a recent common ancestor Superficially similar because these adaptations evolved in response to similar environmental needs Wings of insects & wings of birds

Analogous Structures: These organisms do not share a recent common ancestor, but they have similar appendages that evolved to help them survive in an aquatic environment

D) Vestigial Structures Reduced or nonfunctional structures Examples: appendix, wisdom teeth, human tail bone Interpretation: the vestigial structure was functional in some ancestor of the modern organism Snakes have pelvic bones; they are known to be the descendants of four-legged reptiles

Vestigial Human Structures

E) Similarities in Macromolecules- Proteins MORE differences in amino acid sequences of distantly related species FEWER differences between species that are more closely related Nucleic Acids MORE differences in DNA sequences between distant relatives

DNA sequences Animal Human Gorilla Chimpanzee Orangutan

Three Different Patterns of Evolution 1) Coevolution 2) Convergent Evolution 3) Divergent Evolution

Coevolution When two species are in close association and evolve together. Also when a species evolves as a result of evolution in another species. These organisms may depend exclusively on each other & be highly specialized!

Convergent Evolution When un-related species becomes more similar over time. Example: streamlined bodies and swimming appendages on sharks (fish) & dolphins (mammals)

Divergent Evolution When related species become more different over time. An example is domestic dogs and wolves Divergent evolution is the result of: artificial selection adaptive radiation – where many species evolve from one species

Label what type of evolution is occuring Divergent Convergent Coevolution

Convergent or Divergent?? Homologous structures point to divergent evolution from a common ancestor Convergent: Analogous structures point to convergent evolution as a result of adapting to similar environments

Question: Convergent or Divergent Evolution? Why? Dolphins & Penguins Answer: Convergent Evolution Dolphins are mammals Penguins are birds Both have developed flippers and streamlined bodies to swim & blubber to keep warm in water

Genetic Equilibrium Genetic equilibrium is a theoretical condition where the frequency of alleles (traits) within a population stays the same from generation to generation **** Genetic equilibrium does not exist *****

Five Reasons Why Genetic Equilibrium Does Not Exist Migration Mutations Genetic Drift Non- Random Mating Natural Selection

1) Migration – the movement into or out of a population Immigration – the movement INTO a population Emigration – the movement OUT a population The genes will move also! 22

2) Mutations – the alteration in alleles, or genetic information New traits will form, while harmful traits will eventually be eliminated Creates VARIATION 3) Genetic Drift – by chance, some individuals survive to pass on their genes to their offspring. Has nothing to do with fitness Pure luck Greater effect on a small population than on a large population. 23

4) Non-random mating – organisms tend to mate with others in close proximity; promotes inbreeding and leads to a change in frequencies of certain traits 5) Natural Selection – the fittest will survive; bad traits will be eliminated from the population due to natural selection 24

Tempo of Evolution Gradualism is a process of evolution in which the formation of new species occurs gradually   Punctuated Equilibrium is a process in which the formation of new species occurs rapidly between periods of little or no change Formation of new species is called speciation