HHMI The Beak of the Finch

Different finch species have beaks of different shapes and sizes. What do these beak differences tell us?

• Differences in beak shapes tell us that all the finches eat the same type of food.
• Different finch beak shapes are evidence that all Galápagos finches shared a common ancestor a long time ago.
• Different finch beak shapes are evidence that over time, finch species adapted to different food sources on the islands.
• Different finch beak shapes are evidence that several finch species with different beak shapes came to the Galápagos Islands from the mainland.

How does DNA evidence support the hypothesis that the 13 species of Galapagos finch all came from 1 common ancestor?

• DNA evidence shows that all the finches have similar beak shapes, therefore a common ancestor
• DNA evidence shows that the birds had 1 similar gene in common so they are all from the same common ancestor
• DNA evidence showed that each of the 13 species DNA sequences were more similar to each other than any mainland bird
• DNA evidence shows birds came from 13 different mainland species that all migrated to the island

In 1977, Daphne Major experienced a severe drought. The figure shows the beak depths(sizes) of the initial population of medium ground finches before the drought (red bars), and of the drought survivors (black bars). What does the data show? Select all that apply.

• The most common beak depth of the initial population (red bars) was 8.8 mm. A very small proportion of individuals with this beak depth survived the drought.
• More than half of the initial finch population died during the drought.
• Finch species with larger beaks survived the drought while other finch species went extinct

• Finches with larger beaks had a survival advantage in the dought

The top figure shows the beak depths of the 1976 finch population (red bars) before the drought, and the population after the drought (black bars). The lower figure shows the beak depths of the offspring of the drought survivors in 1978. What do these figures tell us?

• The average beak depth of the 1978 offspring population is larger than that of the original 1976 population.
• The finches that survived the drought (black bars in first graph) had offspring (red bars in second graph) with on average much larger beaks than their parents.
• The offspring (red bars in second graph) had a smaller range of beak depths—from smallest to largest—than their parents (black bars).
• The size of the offspring population in 1978 is much larger than the initial 1976 population, before the drought.

The film defines species as populations whose members don't interbreed. What keeps different Galápagos finch species from mating? Select the 2 that apply.

• Individuals only recognize and respond to songs of their own species.
• One population eats mostly small, soft seeds and the other population eats mostly large, hard seeds.
• Geographic isolation and different environments led to changes in traits that affected mating.

Which is the most likely explanation for the presence of 13 different finch species on the Galápagos Islands today?

• Many years ago, several different species of birds migrated to the islands and the 13 finch species that currently live there are the only species that survived.
• Many years ago, a small population of a single bird species migrated to the islands and evolved into the 13 species that live on the islands today.
• Each of the 13 species has migrated to the islands at different times over the years.

Different finch species have beaks of different shapes and sizes. These different beak structures are evidence of ....

• different finch species adapting to different environments over many generations.
• different finch species with different beak structures coming to the Galápagos Islands from the mainland.
• different finch populations being evolutionarily related.
• . individual birds changing their beak characteristics so that they could feed efficiently.

Examine the phylogenetic tree of the 13 finch species below. Which of the following statements is a correct interpretation of the phylogenetic tree in the illustration?

• The warbler finch is the common ancestor to all the finch species that exist today in the Galápagos Islands.
• The 13 finch species evolved in sequence; the warbler finch is the oldest species and the small ground finch is the most recent species to evolve.
• All the Galápagos finches are more closely related to one another than they are to mainland finch species.

Which of the five statements below describe(s) GEOGRAPHICALLY isolated populations?

• i. The two populations live on different islands.
• ii. One population breeds in late spring and the other population breeds in late summer.
• iii. One population eats mostly small, soft seeds and the other population eats mostly large, hard seeds.
• iv. The males of one population have different mating calls than the males of the other population.
• v. The females of the two populations look the same.

Which of the five observations below provide(s) evidence that two populations are likely experiencing REPRODUCTIVE isolation and that there is little, if any, genetic exchange between them? SELECT ANY THAT APPLY

• i. The two populations live on different islands.
• ii. One population breeds in late spring and the other population breeds in late summer.
• iii. One population eats mostly small, soft seeds and the other population eats mostly large, hard seeds.
• iv. The males of one population have different mating calls than the males of the other population.
• v. The females of the two populations look the same.