KEY CONCEPT New species can arise when populations are isolated.

The isolation of populations can lead to speciation. Populations become isolated when there is no gene flow. Isolated populations adapt to their own environments. Genetic differences can add up over generations. Prior Knowledge: A. How do we know that a 3 foot tall Irish wolfhound and a 6 inch tall Chihuahua are the same species? B. At what point would the two breeds become separate species?

Reproductive isolation can occur between isolated populations. members of different populations cannot mate successfully final step to becoming separate species Speciation is the rise of two or more species from one existing species. Summarize: Why is reproductive isolation considered to be the final stage in speciation?

Reproductive Isolation Example

Populations can become isolated in several ways. Behavioral barriers can cause isolation. called behavioral isolation includes differences in courtship or mating behaviors Example: 2000 species of fireflies are isolated this way. Male and female fireflies produce patterns of flashes that attract mates of their own species (i.e. one flash every second or one every 2 seconds or a double flash every 5.5 seconds.).

Geographic barriers can cause isolation. called geographic isolation physical barriers divide population Fig. The formation of the Isthmus of Panama created a barrier for many marine species. They could no longer cross between the Atlantic and Pacific oceans. Here! Fig. Although snapping shrimp in the Atlantic and the Pacific oceans look similar, they are distinct species that have evolved through geographic isolation. Even when they are brought together they snap at each other and do not mate.

Geographic Isolation Possums of Australia and Opossums of Americas What do they have in common? Do they share a common ancestor? Why are they only found in Australia and the Americas? Explain how Geographic Isolation contributes to their individual differences. Vs.

Geographic Isolation Check your understanding: How did the formation of the isthmus affect marine species? How did the formation of the isthmus affect the land species of North and South America? What might it mean for marine species that there is now a canal connecting the Caribbean Sea and the Pacific Ocean?

Populations can become isolated in several ways Temporal barriers can cause isolation. called temporal isolation timing of reproductive periods prevents mating Example: two tree species that grow on the Monterey peninsula in California are very closely related. However, they have different pollination periods. The Monterey pine sheds its pollen in February and the Bishop pine sheds its pollen in April. These pine species have most likely evolved through temporal isolation. Compare and Contrast: What are the differences and similarities between behavioral isolation and temporal isolation?