Lab: Evolution

Lab: Evolution

Introduction

The Evolution Lab includes seven projects focused on the evolution of beak size (i.e., the depth of the beak) in the medium-ground finch (Geospiza fortis).

Null Hypothesis

The factors affect the depth of the beak by manipulating various biological parameters (initial beak size, heritability of beak size, variation in beak size, clutch size, and population size) and two environmental parameters (precipitation and island size).

Alternative Hypothesis

The factors don't affect the depth of the beak by manipulating various biological parameters (initial beak size, heritability of beak size, variation in beak size, clutch size, and population size) and two environmental parameters (precipitation and island size).

Lab: Evolution

By altering these parameters, we can “design experiments” to infer for yourself how these various factors affect evolution.

The model is quite straightforward and is based on Peter and Rosemary Grant's work that was featured in the video What Wallace Never Saw. Small populations of medium-ground finches occur on two different hypothetical islands - “Wallace Island” and “Wallace Island” where they feed on seeds produced by plants. Three sizes of seeds are available to the finches:

1. Plants that do best under wet conditions produce small, soft seeds - finches having small beaks best exploit this category of seed. When wet conditions predominate, small seeds dominate and finches with small beaks have a higher survival rate.

2. Plants that perform best under moderate precipitation conditions produce intermediate-sized, hard seeds - finches with intermediate-sized beaks optimally handle this category of seed. At intermediate rainfall levels, a mixture of the three seed types are found, with intermediate-sized seeds most abundant; birds with medium-sized beaks survive best under these environmental conditions. (biologylabsonline.com)

3. Plants that dominate during drought conditions produce large, hard seeds - finches possessing large beaks that are able to crack and open hard seeds best use this category of seed. When ...