CLASS SET: PLEASE DO NOT WRITE ON THIS Natural Selection: Butterflies

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1 CLASS SET: PLEASE DO NOT WRITE ON THIS Natural Selection: Butterflies BACKGROUND: Butterflies don t actually eat. Instead of eating, butterflies get their nourishment from drinking. They have a long narrow tube in their mouth called a proboscis that acts as a straw. In this activity, you will model the different patterns of natural selection that occur to a population of butterflies on Nectar Island. The straws represent the proboscis of a butterfly. The flowers that the butterflies drink nectar from are trumpet shaped with the depth ranging from shallow, medium, and deep. The length of a butterfly s proboscis determines what type of flower it can drink from. A butterfly with a short proboscis eats only the nectar from the shallow trumpet flowers. A butterfly with a medium proboscis eats only the medium trumpet flowers and those with a long proboscis eat only from deep trumpet flowers. MATERIALS: Straw of different lengths and colors, ruler, colored pencils SET UP: 1. Take all of the straws out of the Ziploc bag and sort by size. 2. Using a ruler, measure each different sized straw in centimeters. Record the length and number of straws at each length in the tables for both scenario 1 and 2 in the columns labeled length and generation 0. This is your starting population for both scenarios. PART 1 Scenario 1: Non-native rabbits are introduced to Nectar Island. They reproduce like crazy and they like to eat the very shallow trumpet flower plants. Soon, all of these flowers are gone. Since the shallow trumpet flowers are gone, the butterflies with short proboscis start to die from starvation. Once all the shallow trumpet flowers are gone, the rabbits move on to eating the deep trumpet flowers since they don t like the taste of the medium trumpet flowers. Soon the deep trumpet flowers also disappear. 1. When the shallow trumpet flowers are all eaten, most short proboscis butterflies die and do not reproduce. Remove the blue colored straws to simulate this occurrence in your butterfly population. 2. With the deep trumpet flowers gone, the butterflies with long proboscis also die and most do not reproduce. Remove the green colored straws from the population. 3. Multiply the remaining straws of each size by 2 to simulate reproduction of the original population. Record these numbers in your table under the column labeled generation Create a line graph for the two generations in your table. There should be two lines, one for each generation. Color code the lines and create a key and title. Continue to Part 2 on the back.

2 PART 2 Scenario 2: The shallow and medium trumpet flowers live near the edge of the beach while the deep trumpet flowers live farther inland. One day a very strong storm passed over the island, causing enormous waves to hit the beaches and wipe out almost all of the shallow and medium trumpet flowers living there. With the majority of the shallow trumpet flowers gone, the competition between the short proboscis butterflies is fierce and many die from starvation. The same is true of the medium proboscis butterflies on the island. 1. Remove from your butterfly population the blue colored straws to simulate many of the short proboscis butterflies dying off. 2. Remove the yellow colored straws except for one 4 cm length straw to simulate many of the medium proboscis butterflies dying off 3. Multiply the remaining straws of each size by 2 to simulate reproduction of the original population. Record these numbers in your table under the column labeled generation Create a line graph for the two generations in your table. There should be two lines, one for each generation. Color code the lines and create a key and title.

3 Number of Butterflies LABS AND ACTIVITIES Data: Scenario 1 NAME: Natural Selection: Butterflies Number of Individuals Length (cm) Generation 0 Generation 1 Key: Length of Proboscis (cm) Analysis: 1. Which pattern of selection is simulated in this scenario? 2. What environmental pressure caused this selection? 3. Describe how the two lines on your graph differ. 4. Why did the population change in this way?

4 Number of Butterflies Data: Scenario 2 Number of Individuals Length (cm) Generation 0 Generation 1 Key: Length of Proboscis (cm) Analysis: 1. Which pattern of selection is simulated in this scenario? 2. What environmental pressure caused this selection? 3. Describe how the two lines on your graph differ. 4. Why did the population change in this way? CHALLENGE! On a separate piece of paper you will come up with an original scenario which results in disruptive selection. Use any organism you would like. Be sure that all necessary details are included in order to understand why this type of selection occurs. Describe how the population changes in your scenario from one generation to the next. Also include a definition of disruptive selection and sketch a graph with lines for both the original population and the generation after selection.

5 Teacher Set Up For one butterfly population you will need: 6 yellow straws 1 that is 3 cm long, 4 that are 4 cm long, and 1 that is 5 cm long 3 blue straws 1 that is 2 cm long, and 2 that are 3 cm long 3 green straws 2 that are 5 cm long, and 1 that is 6 cm long Each group will need their own butterfly population so I suggest putting each into a Ziploc bag. If you change the colors of the straws make sure you change the colors in the instructions so it will still simulate the same pattern of natural selection.