Learning Exercise

Bird Bills and Natural Selection

This lab illustrates how environmental pressures, such as food shape, can determine the success/fitness of species variants.
Course: biology
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Pictures of the galapagos finches. see more

Exercise

The 5 E's: I. Engagement Teacher will stimulate prior knowledge by quickly drawing a concept map of evolution, Darwin's travels to the Galapagos islands, and natural selection. Students will then write 3 to 4 sentences explaining natural selection in their own words. This will mentally prepare them for the activity they are going to be participating in, and also allow me (the teacher) to see where students are in understanding the concept that has been presented in class. 2 to 4 students will share their responses with the class. The teacher will add key words/phrases to the concept map like fitness and environmental pressures. II. Exploration Students will participate in a Bird Bill experiment. Using various “bird bills” (scissors, clothes pins, forceps, etc.) students will attempt to pick up the most amount of “food” (marbles, toothpicks, etc) as they can in a limited amount of time. This simulation represents the variety of bird bill shapes of the Galapagos finches and the information that Darwin derived from observing these finches. III. Explanation After the game is completed students are to collect the information into a data table, for the entire class. Students will then have to answer a series of questions pertaining to the information they find in the class data chart. IV. Extenstion After students have answered questions, we will have a discussion about what their results mean on a grander scale, and how they could be applied to other species besides finches. V. Evaluation Students will be informally evaluated through discussion, and will be given a score on the lab based on completeness, and relevance. The Lab: Bird Bills and Natural Selection Introduction: Bird bills come in many different sizes and shapes. Each shape is designed for harvesting a certain food type. Some birds eat seeds, some insects, some fish, some land animals, and some eat small marine animals. Each beak is designed for the food the bird eats and therefore it is difficult for a bird that normally eats seeds to change its diet to insects because it can’t change its beak. So if a bird’s food supply runs out, the bird will die or have to move to a new location to find more food. In this activity we will imitate 4 different birds by collecting food with objects resembling their different bills. Some of the bills will be more successful than other bills in collecting certain foods. What will happen to the birds that have bills that can’t harvest very much food? Materials: 20-30 paper cups (stomachs) 50-100 marbles 1 box of toothpicks 200 washers 3-4 paper plates (to hold food) Bird Beaks: 12 Popsicle sticks 6 clothes pins 6 pairs of scissors 6 plastic spoons Procedure: 1. Break up into groups of 4. Each member will have one type of “bird beak.” 2. Each student needs a cup to put their collected food in; this will be considered the bird’s stomach. 3. The teacher will distribute the first food item to each group. 4. When the teacher says go, with only one hand, use your bill to put as many items as you can into your stomach. 5. Record how many items you harvested with your bill, in the proper section of the data table. 6. Complete steps 3-5 for each food item. 7. When all the food items are finished, gather as a class to collect the data into one table. Type of Bill Marbles Washers Toothpicks Popsicle Sticks Clothespins Scissors Spoons Questions: 1. Which bill type captured the most number of prey items (food)? 2. Which food type is each bill type best adapted to? Popsicle sticks: Clothes pins: Scissors: Spoons: 3. Which bill type is the most generally adapted to the food supply? 4. If the environment changed and killed off all of the other food sources except marbles, which bird would be most successful? What would happen to the other birds? 5. If your bill was shaped like a Popsicle sticks, what adaptation would have to occur in order for you to compete with spoons in feeding on marbles? 6. Create a bill shape from a household item that would be very successful with all 3 food shapes? Homework** 7. Please give another example of natural selection in action and explain how your example is similar to the Galapagos finches.

Technical Notes

There are several materials needed (marbles, washers, etc.) that are not found in the typical science classroom.

Requirements

Students must have been introduced to the theory of evolution, natural selection, fitness, and Darwin's travels to the Galapagos Islands.

Topics

The California state standards covered is Biology/Life Science grades 9-12 8a) Students know how natural selection determines the differential survival of groups of organisms.

Learning Objectives

Students will be able to explain how environmental pressures have shaped the evolution of Galapagos finches. Students will also be able to relate the fitness of these finches to the evolutionary history of life on Earth.

Assessment

Formative for the discussion and a small grade for lab completeness.