Preview - Evolution Of Populations To Speciation (Advanced)

Introduction to Galapagos Finches


There are 13 species of finch on the islands, but they are at once both so similar and so diverse that they have provided a fertile ground for exploring evolution since Darwin’s 1835 visit.  Darwin himself did not realize their role in explaining evolution until after ornithologists revealed the abundance of speciation to him.

Let's watch a video developed by Howard Hughes Medical Institute based on data collected by Peter and Rosemary Grant, Princeton University.

The finches are proposed to have arrived on the volcanic islands from the South American mainland and are now considered part of the tanager family rather than the finch family.  There are four genera recognized in the group, and the species occupy overlapping but distinct ecological niches. In the genus Geospiza, there are six species.  In good times, they often eat the same foods, but in times of scarcity, each species has a specialized niche – large seeds, cactus fruits, etc. – on which they rely.  Their mating behaviors, such as times and songs, differ greatly, maintaining the distinct species.  The ecology of the different islands influences which species live on each island, and especially which species co-exist on an island.  Gene flow between islands occurs with occasional immigrants depending on storms and the distance between islands.

For several decades, scientists have gone to the Galapagos islands to study the physical characteristics of the finches there.  They recorded data on many traits including beak dimensions and weight.  In this lesson you will explore some of that data to understand the processes underlying speciation and adaptive radiation.


Questions

Please answer the questions below.

What do you think separates species from each other?  In other words, what does it mean to be a 'different species' than another organism?


How would you go about trying to distinguish one species from another?


Why do you think the data the scientists collected might be useful for studying differences between species?


Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.