Chapter 17.3

How can reproductive isolation develop?

it can develop from behavioral, geographic, or temporal isolation

What happens when a gene pool splits?

the changes in one gene pool can't spread to the other

What is speciation?

the formation of a new species

What causes a gene pool to split?

the gene pool splits if members of the population stop breeding with other members of the population.

What happens when a population becomes reproductively isolated?

they can evolve into two separate species.

Why is there competition for two species of finches living in one are?

they compete for seeds because during the dry season, birds that are the most different from each other have a higher fitness since more specialized birds have less competition. Over time, species evolve in ways to increase the differences between them.

What is an example of temporal isolation?

three similar species of orchid species live in the same rainforest. They all have flowers that last one day so they must be pollinated on that day to make seeds but the three species bloom on different days so they cannot pollinate each other

What is temporal isolation?

when two or more species reproduce at different times

What is geographic isolation?

when two populations are separated by geographic barriers such as rivers, mountains, and bodies of water

What is reproductive isolation?

when two populations no longer interbreed and produce fertile offspring

What is behavioral isolation?

when two populations that are capable of interbreeding develop differences in courtship rituals or other behaviors

What hypothesis did Peter and Rosemary Grant come up with?

According to their hypothesis: the speciation in the Galapagos finches occurred by the founding of a new population, geographic isolation, changes in the new population's gene pool, behavioral isolation, and ecological competition

What is an example of geographic isolation?

Albert's squirrels live the South West. 10,000 years ago, a small population of the Albert's squirrel became isolated on the North rim of the Grand Canyon forming separate gene pools. Natural selection and genetic drift separately worked on each group creating a subspecies called the Kaibab squirrel. Both of these species of squirrels are very similar but they differ in fur color

Explain how the vegetarian tree finch, which feeds on fruit, might have evolved

Finches that ate seeds or insects may have arrived on an island where fruit was avail-able. Birds with beak variations that made them better-suited for eating fruit would have been favored by selection. Eventually, selection might have led to the evolution of a new species of fruit-eating finches

What types of reproductive isolation may have been imporatant in Galapagos finch speciation? Explain.

Geographic isolation may have been important initially as populations of finches became separated on different islands, because they would no longer share a common gene pool. Later, if different species lived in the same place, behavioral isolation may have been important. The birds now had different-sized beaks and would not mate with each other, so their gene pools remained isolated

Explain why reproductive isolation must occur for separate populations of the same species to evolve into different species.

Reproductive isolation must occur so that the gene pools are isolated. When the gene pools are isolated, changes that occur in one gene pool will not be carried over to the other gene pool. Thus, over time, accumulated gene pool changes can produce a new species.

A botanist identifies two distinct species of violets growing in a field. Also in the field are several other types of violets that, although somewhat similar to the two known species, appear to be new species. Develop a hypothesis explaining how the new species may have originated.

Sample answer: The new species originated from the two known species by becoming reproductively isolated, perhaps by flowering at different times, and then had different mutations and selective pressures.

A newly formed lake divides a population of a beetle species into two groups. What other factors besides isolation might lead to the two groups becoming separate species?

Sample answer: the founder effect and varied selection pressures in different environments

How did geographic isolation affect the finch population?

Some finches from the original population on the mainland flew to other islands. Because finches rarely fly over open water, they don't usually move islands becoming geographically isolated.

How is time a factor in temporal isolation?

Temporal isolation occurs when two or more species reproduce at different times, such as different times of day or days of the year

Suppose a seamount forms from an underwater volcano. Birds on the mainland colonize the island. How might this lead to speciation?

The birds on the island may become reproductively isolated from mainland birds through geographic isolation. As a result, the gene pool of the birds that colonized the island would remain isolated, and the birds may evolve to become a new species as they adapt to their island habitat

What is a species?

a population or group of populations whose members can interbreed and produce fertile offspring

How did the founder effect affect the original species of finches that came to the Galapagos from South America?

because of the founder effect, allele frequencies in the founding population are different from the South American population

What is an example of behavioral isolation?

eastern and western meadow larks are similar birds with habitats that overlap but they won't mate with each other because they use different songs to attract mates

How can geographic barriers link species?

for example, if theres a flood, it can link separate lakes allowing fish populations to mix.

How do the finches on the Galapagos islands become behaviorally isolated?

If one finch population from an island were to fly back to the mainland where the original finch population is, they probably won't mate because finches carefully choose their mate. In courtship, the finches inspect their partner's beak favoring ones with the same beak size as them. because both populations evolved different beak sizes, they won't mate with each other.

Explain why reproductive isolation usually must occur before a population splits into two distinct species?

If populations are not reproductively isolated, genetic changes continue to spread among individuals through interbreeding. Only after reproductive isolation can genetic changes cause a divergence between gene pools and, therefore, speciation

What must happen in order for a new species to evolve?

Populations must be reproductively isolated from one another

How did the gene pools of finch populations on the Galapagos islands change?

overtime populations on the islands adapted to local environment based on the resources available. For example on island 1, small, thin-shelled seeds were more common and on island 2, large, thick-shelled seeds were more common. On each of these islands, directional selection would favor individuals with smaller or larger beaks causing the population to evolve smaller or larger beaks overtime creating two new species