Exam (elaborations) GIZMOS Rainfall and Beaks gizmo

Exam (elaborations) GIZMOS Rainfall and Beaks gizmo Vocabulary: adaptation, beak depth, directional selection, drought, evolution, natural selection, range, stabilizing selection Prior Knowledge Questions (Do these BEFORE using the Gizmo.) During the voyage of the HMS Beagle (1831–1836), the young Charles Darwin collected several species of finches from the Galápagos Islands. Two of Darwin’s finches are shown below. 1. Which species do you think is best adapted to a diet of small, delicate seeds? Explain why you think so. Geospiza fortis, because it has a smaller beak with a fine point that could pick up delicate seeds. 2. Which species do you think is best adapted to a diet of large, toughto-crack seeds? Explain. Geospiza magnirostris, because it has a larger, stronger beak that crush the seed shells easily. Gizmo Warm-up Darwin’s finches are one of many types of animals on the Galápagos Islands that have unique adaptations, or traits that help an organism survive in its environment. The Rainfall and Bird Beaks Gizmo™ allows you to explore how rainfall influences the range of beak shapes found in a single finch species. 1. The beak depth of a finch is the distance from the top of the beak to the bottom, as shown. A. What is the current average beak depth in the Gizmo? 10.04 mm B. Select the HISTOGRAM tab. Do all the finches have the same beak depth? No! 2. Click Play ( ) and let the simulation play for five years with average rainfall (12.5 cm/yr). Select the GRAPH tab and view the Finches vs time and Beak depth vs time graphs. A. How does the finch population change? The population varies in an almost sinusoidul shape, with the population going down in number and then up again. This study source was downloaded by from CourseH on :18:46 GMT -05:00 This study resource was shared via CourseH GIZMOS Rainfall and Beaks gizmo B. Does the beak depth change significantly? Yes, the beak depth decreases significantly. The beak depth went from 10mm to 7.5 on average over the 5 years. This study source was downloaded by from CourseH on :18:46 GMT -05:00 This study resource was shared via CourseH Activity A: Normal years Get the Gizmo ready:  Click Reset ( ). Introduction: The Galápagos Islands are very dry, with an average rainfall on some islands of about 12 centimeters per year. The amount of rainfall has a large impact on the abundance and types of seeds that are available to be eaten by finches. In the process of natural selection, only the finches that are best adapted to the available seed types survive and have offspring. Question: How is the finch population affected by a period of average rainfall? 1. Observe: With the Rain sliders set to 12.5 cm, click Play, and then Pause ( ) after one year has passed. Select the TABLE tab and look at the Month and Finches columns. A. How did the finch population change over the course of one year? It increased, then decreased. Overall decreased by 240. B. The finches have their young during the rainy season. Based on the table, which part of the year do you think is the rainy season? The 5th month had the highest population, so it’s likely the spring/may is the rainy season. 2. Analyze: Click Reset, and choose the HISTOGRAM. The bars represent the numbers of finches that have different beak depths. The range of beak depths is equal to the difference between the largest and smallest beaks. A. What is the average beak depth of the current finch population? 9.72 mm B. What is the range in beak depths in the population? 8 mm. C. Do most of the finches have beak depths near the lower extreme, the middle, or the higher extreme of the range? Near to the middle. 3. Experiment: Click Play, and observe the histogram as the simulation plays for five years. A. What is the average beak depth now? 7.9 mm B. What is the current range of beak depths? 7mm C. Based on what you have seen, are finches with very small, medium, or very large beaks most likely to survive in times of normal rainfall? Justify your answer. If set at 2 inches of rain, the lowest value, the beaks are about 12.64 mm on average. If set at 20 inches, the highest value of rain, the beaks are an average of 7.24 mm. At average rainfall, the beaks are 10.34 mm. Thus, finches with medium beaks are most likely to survive in times of normal rainfall. This study source was downloaded by from CourseH on :18:46 GMT -05:00 This study resource was shared via CourseH Activity B: Drought Get the Gizmo ready:  Click Reset. Introduction: In years of extreme drought, Galápagos plants don’t produce new seeds. The small, delicate seeds get eaten up quickly, leaving behind only the largest, toughest seeds. Question: How does drought affect the finch population and average beak depth? This study source was downloaded by from CourseH on :18:46 GMT -05:00 This study resource was shared via CourseH 1. Form hypothesis: What type of beak do you think will be best for finding food in a drought? To eat the largest, toughest seeds that are left, finches with the strongest and biggest beaks will have the advantage. 2. Predict: Select the HISTOGRAM tab. On the left side below, sketch the current histogram and list the average beak depth and range of beak depths. On the right side, sketch what you think the histogram will look like after five years of drought. Explain your prediction. Initial beak depths Beak depths after 5 years (predicted) Initial number of finches: 1000 Initial average depth: 9.97 mm Initial range of beak depths: 7 mm Explanation: I predict that the beak depths will be much deeper after the 5 years of little rain. 3. Experiment: Use the sliders to set the Rain to 2.5 centimeters for each of the five years in the simulation. Click Play, and wait for five years. Observe the beak of the finch. A. How does the beak depth change over time? It increases for the first two years, then plateus for the next three years. B. What is the final average beak depth? 12.24 mm. C. What is the final range of beak depths? 3mm. (Activity B continued on next page) This study source was downloaded by from CourseH on :18:46 GMT -05: