Evolution Change in life on Earth

Evolution Phylogeny : the evolutionary history of a group of organisms. Often drawn as a tree

Jean Baptiste Lamarck Early contributor to the theory of evolution. His ideas are summarized as “use and disuse”.

Charles Darwin English naturalist Traveled the world for 5 years on the HMS Beagle Darwin first produced evidence of evolution of living things from a common ancestor

Charles Darwin Darwin identified natural selection as the process for evolution. Natural selection : mechanism for change in populations.

Natural Selection Natural selection proceeds in steps 1. In nature, organisms produce more offspring than can survive.

Natural Selection 2. Individuals have variations. This may be color, size, or speed

Natural Selection 3. Individuals with certain useful characteristics (variation) survive in a struggle for existence.

Natural Selection 4. Over time, the more successful variations are “selected” and the species will gradually change.

Natural Selection This gradual change in characteristics changes the population’s gene pool. Gene pool : all available genes for a population

Evidence of Evolution Fossils provide a record of early life. Fossils of a species can show change over time.

Evidence of Evolution Homologous structures: structures with the same evolutionary origin. Can be the same in arrangement, function or both.

Evidence of Evolution Embryology : the study of the developing embryo. The shared features of the young embryos suggest evolution from a common ancestor.

Evidence of Evolution Vestigial structures : a structure in a present day organism that no longer serves its original purpose. Probably useful to its ancestor

Evidence of Evolution Biochemical : nearly all organisms share DNA, ATP and many enzymes. The code for amino acids is the same in organisms. The more similar the DNA between 2 organisms, the more closely related

Results of Natural Selection Speciation : new species is formed when similar populations no longer interbreed. Species: group of organisms that can breed and reproduce Some obstacle may separate populations.

Results of Natural Selection

Diversity : a large variety of organisms. The more diversity the healthier the ecosystem.

Results of Natural Selection Genetic Drift : Change in gene frequency. (how often you see a trait) Especially in small populations. Recessive trait is expressed Results in a decrease in diversity.

Polydactyl

Results of Natural Selection Divergent evolution: related species become less alike.

Results of Natural Selection Convergent evolution: unrelated species become more alike.

Results of Natural Selection Extinction : species may vanish Can be a mass extinction like dinosaurs.

Paths of Evolution Gradualism : gradual change over time in a species

Paths of Evolution Punctuated equilibrium : relatively quick evolution followed by long periods of equilibrium. Big change in environment, or new predator