Notes

1. Who were the scientists that researched the Galapagos Islands?

Biologists Peter and Rosemary Grant researched the Galapagos Islands.


2. Describe the diversity of islands and the finches that lived on them.

The volcanic islands vastly differ from one another in size, topography, and in height. Islands at higher elevations have tall trees and lower islands have cacti and grasses. The islands are home to thirteen separate finch species.


3. Choose 3 finches and describe their beak and what food they eat on the island.

The warbler finch has a needlelike beak to stab and pick up insects for food. The woodpecker finch has a robust beak and eats the larvae of beetles and termites. Cactus finches have long, sharp beaks to probe into cactus flowers.


4. Explain how the scientists believe the finches arrived on the Galapagos Islands.

The scientists believe that the finches evolved into their separate species once arriving on the island as a singular species. There is DNA proof that the finches likely diversified from a common ancestor into the thirteen species once on the island rather than arriving as separate preexisting species.


5. How did the scientists collect data of the finches?

The scientists routinely netted the medium-sized finches each morning, measuring each finch's beak and weight while tagging them for identification. They tracked over a thousand finches over the years of their studies.


6. What event first occurred to change the island drastically during the time the scientists were researching the finch?

A terrible drought began in 1977, and the island's vegetation (other than cacti) almost entirely disappeared.


7. What observations did the scientists make about the survivors?

The scientists observed that when the drought diminished the island's food supply, the finches began to compete for food. Small seeds were rare, so large seeds had to be eaten; only the birds with larger beaks could easily eat the large seeds, to birds with smaller beaks suffered and died off. The birds with the largest beaks had the highest probability of surviving the drought, and natural selection increased the average beak size.


8. What second event occurred and how did it affect the finch birds?

In 1982, an unusually strong El Nino brought an immense amount of rain. This caused the island to become overgrown with vines, but these vines dried out and left very few large seeds behind when a drought hit a few years later. The birds with larger beaks struggled to eat the available small seeds, and the birds with smaller beaks were able to eat the seeds easily. In short, natural selection switched the advantage trait, making small beaks the favorable trait in the Galapagos.


9. Explain speciation and how one finch has led to 13 different species.

Speciation occurs when two populations become geographically separated and differentiate in their respectively distinct habitats, to the point that the two populations' individuals will not mate together if in contact again in the future. Because the Galapagos Islands are so diverse and often undergo dramatic environmental changes, the finches on the islands have evolved with distinct traits and no longer mate as one population, making them the different species known to live on the Galapagos today.


10. How does song and behavior relate to finch speciation?

Finch species sing distinct songs and only respond to their respective songs. The finches also choose mates with similar beaks and body sizes and ignore other finches that are different than them in the context of these characteristics.