My Science Box backup 2010-03-27-02-31-bQvTz

Overview 

Summary
Inspired by observations of finches on the Galapagos Islands, Charles Darwin came up with an idea that is perhaps the most influential idea in all of science - natural selection. In this classic activity, students learn about natural selection by becoming birds foraging for food on an island (a large area of the schoolyard or classroom). The prey (beans) vary in their coloration such that some blend into the environment better than others. The birds vary in the type of beak they have (plastic forks, spoons and knives). Each season, any prey that survives has a baby bean the same color as the parent. In addition, the most successful birds has a baby with the same beak trait while the least successful birds die (and are reincarnated as the babies of the successful birds). Over several generations, the bird and bean populations shift depending on the environment. Well camouflaged beans survive and reproduce. Birds with beaks that can easily capture beans survive and reproduce. In this way, students model natural selection in 2 species and get a very good idea of how natural selection works.

Summary
Variation in a population is the raw material on which natural selection works. How do scientists measure and quantify variation in traits? We use garden snails as a model organism in order to describe and measure several different traits. Groups are given a small population of snails and must devise an objective way to measure a trait of their choosing (length, mass, speed, color intensity, stripes, withdrawal reflex reaction time, number of pennies it can carry, etc.). There are many ways to extend this activity. For instance, scientific protocols may be traded between groups, hypotheses may be made concerning what individuals will survive better in different environments, and snails may be tagged and released into one or more environments and the populations monitored over time. A long term open-ended project such as this provides a natural extension and assessment opportunity for both evolution and ecology concepts.

Summary
The management of the world’s fisheries is a controversial current issue that involves individuals from many different viewpoints – fishermen and women, environmentalists, park rangers, politicians, and shoppers at the seafood counter. The issue is that many of the world’s fisheries are overfished and have collapsed or are on the verge of collapse. This is but one example of the tragedy of the commons – where a limited common resource is overused because each individual person thinks, “If I don’t use this resource first, then somebody else will.” Students in this activity act as fishermen and women who need to share an ocean of fish and take in a catch. Groups soon realize that if they don’t set fishing limits and monitor the fish population, soon there are no fish left in the ocean.

Summary
Once students understand the concept of populations, it is important to introduce the idea of population change. There are many reasons for population change – limited resources, predator-prey cycles, human impact, habitat change – to name but a few. In this activity, students learn to graph population data and then use their graphs to evaluate one of the most famous examples of population change, the predator-prey population cycle of the snowshoe hare and the Canada lynx. The data is taken from the 300 years worth of real data collected by trappers of the Hudson Bay Company. This activity provides students a chance to look at real data and make some hypotheses about what causes population change in the real world. The Going Further section is more extensive than for other lesson plans on this site and refers teachers to many excellent population change activities that can be found in other curriculum guides.