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Speciation. Family Trees Show relationships between species. Human Evolution. Humans did not evolve from chimpanzee. Humans and chimps share a common ancestor. Defining a Species.

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Family Trees

Show relationships between species.

human evolution
Human Evolution
  • Humans did not evolve from chimpanzee. Humans and chimps share a common ancestor.
defining a species
Defining a Species
  • A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions.
  • For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridiongrallator.
defining speciation
Defining Speciation
  • Speciation is a lineage-splitting event that produces two or more separate species.
  • Branching point on the tree, is a speciation event.
  • At that point genetic changes resulted in two separate fruit fly lineages, where previously there had just been one lineage. But why and how did it happen?
convergent evolution
Convergent Evolution
  • the independent evolution of similar structures in species, often due to similar lifestyles and selection pressures.
analogous structures
Analogous Structures
  • Separate evolutionary origins
  • Similar because they evolved to serve the same function. (they both fly)
  • Analogies are the result of convergent evolution.
  • Characters in different organisms that are similar because they were inherited from a common ancestor
  • Birds, bats, mice, and crocodiles all have four limbs. Sharks and bony fish do not.
geographic isolation
Geographic Isolation

Flies are living on

A group of Banana’s

A storm carries them

To a different island

The flies are separated

And can no longer breed

With the mainland flies

reproductive isolation
Reproductive isolation
  • The evolution of different mating location, mating time, or mating rituals:Genetically-based changes to these aspects of mating could complete the process of reproductive isolation and speciation.
punctuated equilibrium
Punctuated Equilibrium
  • Generally Evolution is slow, changing over millions of years.
  • Sometimes a rapid change in the environment results in burst of new species.
adaptive radiation
Adaptive Radiation
  • Organism’s that share a common ancestor and adaptive to different environments.