3/10/14 Objective: How does geographic isolation and adaptive radiation contribute to species diversity? Do Now: Why are these two animals considered to be 2 different species?

Speculate: Some evidence shows that tigers and lions evolved from a common ancestor, how did they become separate species?

Speciation The origin of a new species Occurs when a small group of individuals separate from main population

Geographic Isolation Can lead to speciation when a population gets separated by a barrier

Allopatric Speciation Populations separated by a geographic barrier form new species (ex: islands)

Adaptive Radiation The emergence of numerous species from a common ancestor introduced to new environments (ex: Darwin’s finches)

Timing of speciation

Gradualism Model Darwin thought evolution was gradual Differences gradually evolve in populations as they become adapted to their environment

Punctuated Equilibrium Abrupt episodes of speciation punctuating long periods of little change or equilibrium

Geologic Time Scale Organizes earth’s history into 4 eras Marked by mass extinctions Eras are divided into periods (marked by lesser extinctions)

Relative Dating The layers of rock chronicles the relative age of fossils

Radiometirc Dating Determines the ages of rocks and fossils Based on the measurement of certain radioactive isotopes C14