Question

the beak of the finch

1. which experimental data from the film provide the best evidence that the cactus finch and the medium ground finch on daphne major are distinct species?

a. many more medium ground finches than cactus finches died in response to the drought.
b. cactus finch and medium ground finch males attempted to breed only with females of their own species.
c. the cactus finch and medium ground finch feed on different types of food.
d. medium ground finch and cactus finch females have different markings and feather color.

1. imagine you are studying a population of finches on one of the galápagos islands. you have been recording many of the birds physical traits, including the length of both wings. you observe that for 80% of individuals measured, the length of the left wing is not significantly different from the length of the right wing (in other words, they are symmetrical). but for about 20% of birds measured, the wing lengths are asymmetrical. this distribution is true from generation to generation. suddenly, a rare 5 - day windstorm takes over the island. after the storm, you spend the next several days netting each bird on the island that survived the storm. you discover that 85% of the birds with symmetrical wings survived the storm, whereas only 5% of the birds with asymmetrical wings did.

a. propose a hypothesis to explain this observation.
b. if such storms become increasingly common due to changes in climate, how might you expect the population to change over time with respect to wing symmetry?

1. which of the five statements below describe(s) geographically isolated populations? select the appropriate answer, a - d.

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.
a. statement i only
b. statements i and iv only
c. statements ii, iii, and v only
d. statement iv only

Explanation:

• Question 4:
• According to the biological species concept, a species is a group of organisms that can interbreed and produce fertile offspring. If cactus finch and medium ground finch males only attempt to breed with females of their own species, it indicates that there is no gene flow between them, which is a key characteristic of distinct species.
• Option a (difference in death - rate due to drought) is about survival in a particular environmental condition, not about species - distinction.
• Option c (difference in food type) is an ecological difference, not a species - defining characteristic.
• Option d (difference in markings and feather color) is a morphological difference, but not the best evidence for species distinction compared to reproductive isolation.
• Question 5a:
• Birds with symmetrical wings may have better flight performance. During a windstorm, better flight performance could be an advantage for survival. For example, symmetrical wings might provide more stable flight, allowing birds to better navigate through strong winds, find shelter, or avoid obstacles.
• Question 5b:
• If such storms become common, natural selection will favor birds with symmetrical wings. Over time, the proportion of birds with symmetrical wings in the population will increase. This is because birds with symmetrical wings have a higher survival rate (85% vs 5% in the storm scenario), and thus are more likely to reproduce and pass on the genes related to wing symmetry.
• Question 6:
• Geographical isolation means that populations are separated by a physical barrier. Populations living on different islands (statement i) are geographically isolated.
• Statement ii (difference in breeding time) is a temporal isolation.
• Statement iii (difference in food type) is an ecological isolation.
• Statement iv (difference in mating calls) is a behavioral isolation.
• Statement v (similar female appearance) is not a form of isolation.

Answer:

• Question 4: B. Cactus finch and medium ground finch males attempted to breed only with females of their own species.
• Question 5a: Birds with symmetrical wings have better flight performance, which helps them survive windstorms better.
• Question 5b: The proportion of birds with symmetrical wings in the population will increase over time.
• Question 6: A. statement I only