Species Produces new types of Organisms,

Coauthored by Linnea Langusch and Andrew Kieckhefer

• Speciation is the process by which new species are generated.

• The main mode of species formation is allopatric speciation, formation due to physcial separation of populations over some geographic distance.

• When a mutation arises in the DNA of an organism in one of the isolated populations, it cannot spread to the other populations. Over some time, each population will have its own mutations.

• The mutations will eventually not allow the populations to breed with each other, ultimately, creating two different species.

• If environmental conditions happen to be different for the two populations, then natural selection could speed up the divergence.

Populations can be Separated in many ways

• We can infer the History of Life's diversification by Comparing Organisms

• Phylogenetic trees, or cladograms are treelike diagrams used to illustrate the history of divergence.

Cladograms display scientists' hypotheses about how divergence occurred.

• Used by analyzing patterns of similarity of genes or external features of species, then mapping traits on a tree. This allows for traits to be traced and to see how they may have evolved.

• Evolutionary Biologists study the patterns of diversity at levels above the species level.

Evolution, Biodiversity, and Population Ecology

• Glacial ice sheets may move across continents during ice ages and split populations in two.

• Dry climate may partially evaporate bodies of water.

• Warming or cooling temperatures may cause vegetation to move, creating a whole new plant and animal distribution.

• Speciation requires how many generations to occur?

• Geologic or climate processes that isolate populations can reverse, allowing populations to do what?

• What can populations do if they have not diverge too much? What happens if the divergence is significant?

• Sympatric speciation occurs when populations become reproductively isolated within the same geographic area. Can be caused due to mutations in chromosome numbers.