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

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