Having a clear understanding of how reproduction over geological time periods leads to the creation of new species and the extinction of others is central for a student’s perception of natural selection and evolution.
For example, birds as a group gained many advantages by taking to the air and the adaptations they evolved to achieve flight are excellent examples of evolution and natural selection at work. Seabirds in particular, have evolved the harsh lifestyle needed for life at sea. Even though, most of the earth is covered by ocean, from the nearly 10,000 bird species in the world today, only a few (~300) call the ocean home.
The goal of our activity is three-fold. First, I want to give a simple and easy to remember explanation of evolution as: ‘time, sex and survival’. Time goes by, animals breed and variations occur with only those animals having variations helping their survival making to a reproductive age. Here I need to explain how long these periods of time can actually be and then explain how variations in individuals are selected by natural selection, leading to new species and the amazing diversity of species see on earth today.
Second, I will use the adaptations seabirds have evolved to make life at sea possible as examples for evolution and natural selection. To put it simply, when living in the ocean and searching for food, birds either travel long distances or dive underwater; two very distinct lifestyles evolving from one common ancestor. Here I will explain how the life-style of a seabird dictates the shape and size of its wings.
And third, by measuring the wingspans, and wing loading of species with different natural histories I will illustrate how biologist take measurements from animal specimens and teach students how to read and interpret a logarithmic graph showing how wing surface area increases as a function of bird weight. Using preserved wings from four to five seabird species with different natural histories, I will propose to the students to use their new knowledge of seabird morphology and natural history, and take measurements from these wings and interpret those measurements and hypothesize what species they come from.