Formation of Species 16.3 pp. 309-312 Speciation = formation of new species of organisms by evolving from an ancestor Morphological Concept: Morphology = internal & external structure and appearance Morph = change the look Plus: Convenient, works with extinct species Minus: Easy to make mistakes Populations evolve, individuals do not evolve.

Formation of Species 16.3 pp. 309-312 Biological Species concept = individuals of a population can successfully interbreed and cannot interbreed with other populations Offspring are fertile Plus: testable for living species; improved by DNA analysis Minus: can’t apply to non-living organisms Not this case:

Formation of Species 16.3 pp. 309-312 Isolation = populations are separated which may lead to speciation Ways to separate: Geographic isolation = different places Temporal isolation = different times Reproductive isolation = don’t mate

Formation of Species 16.3 pp. 309-312 2 categories of Reproductive Isolation: 1. Prezygotic = before fertilization (before a zygote) Different behavior Different times (temporal) Different habitats (geographic) 2. Postzygotic = after fertilization (after a zygote) Mutation Infertility of offspring

Formation of Species 16.3 pp. 309-312 Rates of Speciation = how fast does a new species evolve Rough average is 1 every million years but this can vary greatly Depends on selection pressures in the environment

Formation of Species 16.3 pp. 309-312 Rates of Speciation Gradualism = slowly over time (~ million years) Mutation Isolation 2. Punctuated Equilibrium = periods of sudden evolution caused by extreme selection pressures, followed by periods of no evolution (~ thousands of years)