The purpose of this lesson is to learn how the combination of mutations, natural selection, and environmental change generate progressively better-suited adaptations.

Purpose  
So far we have studied how environmental changes affect population of species. In this lesson, we will explore how new species emerge.

Brainstorm
You know that many species that were alive in the past have gone extinct.  Many of the species that are alive today did not exist at one point in the past.  

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.

Below is a data analysis tool called CODAP created by educators at the Concord Consortium. Using this computational tool, you will be able to delve deeply into the finch data mentioned on the previous page. When the page loads you will see the basic finch dataset with columns for sex, weight (g), beak length (mm), beak depth (mm). In CODAP we are able to interact dynamically with the data, allowing us to make connections and draw conclusions. We will use this set to answer several questions about these Galapagos finches.

The scientist that have collected this data have done so for over 40 years now, the first bar graph that you saw in section one contains finch data from 1973 -1981. Lets see what we can find if we look deeper into the data.

In this data set, "Last Year" is the record of the last year an individual finch was seen by the researchers.  This typically means that the individual finch died during that year.

Use the methods you learned in the last activity to compare the finches that died during 1977 with the finches that survived 1977 and answer the questions below.

This CODAP frame has a much larger data set than those you have explored in the previous activities.  To help you gain a better understanding of the finches in the Galapagos, there are many more physical traits to explore.  Use the skills you developed in the previous activities to use CODAP to look at several traits and compare them across species and locations.

Not all of the traits were measured on each individual, so some traits will have more complete information than others.  We will focus on a trait that has a lot of data points, beak height.