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ANSWERS Chapter 1 Worksheet for Case Study in the Process of Science #1 How Do Environmental Changes Affect a Population of Leafhoppers? Instructions 1. Go to www.campbellbiology.com or the Essential Biology student CDROM. 2. Select Chapter1 from the pulldown menu. 3. On the left, click on "Case Studies in the Process of Science." 4. Click on "How Do Environmental Changes Affect a Population of Leafhoppers?" 5. Read the text in the upper right, and follow the instructions. Instead of typing your
Lab Notebook Global Warming Data Table Number of: Large Parental 2 generation 10th 0 generation 20th 0 generation 30th 0 generation
Size Medium 22
Color Small 2
Black 22
Brown 3
20
5
25
0
10
15
25
0
3
22
25
0
Graph your Global Warming data, using this key: __________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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•
Black leafhoppers = X Brown leafhoppers = X in color
Large leafhoppers = Medium leafhoppers = O Small leafhoppers = •
Predator Change Data Table Number of: Size Large Medium Parental 1 22 generation 10th 1 23 generation 20th 1 23 generation 30th 0 25 generation
Color Small 2
Black 22
Brown 3
1
15
10
1
10
15
0
2
23
Graph your Predator Change data:
__________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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Vegetation Change Data Table Number of: Size Large Medium Parental 2 22 generation 10th 1 23 generation 20th 0 25 generation 30th 0 25 generation Graph your Vegetation Change data:
Color
Pesticide Application Data Table Number of: Size Large Medium Parental 2 22 generation 10th 5 20 generation 20th 10 15 generation 30th 23 2 generation
Small 1
Black 22
Brown 3
1
23
2
0
24
1
0
25
0
Color Small 1
Black 22
Brown 3
0
24
1
0
25
0
0
25
0
Graph your Pesticide Application data: __________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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Lab Report 1. What role does genetics play in the variation seen in this leafhopper population? Different forms of genes in the leafhopper population provide the variety of characteristics seen. 2. Note the results from the 20th generation under global warming conditions. Before continuing with the 30th generation, predict the population composition of the 30th generation. One would expect a loss of lighter colored (brown) and larger leafhoppers leading to a population predominated by darker, smaller leafhoppers. 3. What happened to the proportion of each type of leafhopper in subsequent generations under global warming conditions? Suggest a reason why the traits of the 30th generation make this population better adapted to its altered environment. There were fewer orange and large leafhoppers and more small leafhoppers. Perhaps the snall leafhoppers have a metabolism better suited for global warming, e.g., smaller leafhoppers may dissipate heat better than larger ones. Metabolic differences in the lighter colored leafhoppers may explain their demise. Perhaps they did not survive as well as the darker ones because they needed more calories of energy to produce offspring in a warmer climate. Color may not always play a direct role in survival, but may be linked to other characteristics that are passed on to subsequent generations.
__________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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4. Why would you expect a change in predators to cause a difference in the types of leafhoppers being selected? Each predator has a different strategy for finding its prey. Birds and snakes hunt differently and would select leafhoppers with characteristics fitting to their foraging strategy. 5. Note the differences between the parental, 10th and 20th generations when the predator changed from a bird to a snake. What evidence supports the view that leafhopper size is not affected by a change in predators? It appears from the data that birds favor the light colored leafhoppers and snakes favor the dark colored ones. There is no gain or loss in the proportion of small or large leafhoppers for each generation. 6. What happened to the proportion of each type of leafhopper in subsequent generations when the predator changed from a bird to a snake? Suggest a reason why the traits predominant in the 30th generation make this population better adapted to the change in predators. There are now more light colored leafhoppers than dark colored ones. Snakes regularly selected the dark colored leafhoppers and shifted the population characteristics from predominantly dark colored to light colored. 7. Describe some human activities around your school that could have influenced the natural vegetation in the area. Examples: land clearing for housing, college buildings, commercial buildings. 8. Note the differences between the parental and the 30th generations. What happened to the proportion of each type of leafhopper when the vegetation changed? Suggest a reason why the traits of the 30th generation make this population better adapted to its altered environment. The leafhopper population was selected for uniformly medium sized dark bodied individuals. Those individuals making up the population may possess a metabolism that is adapted to eating the new food source. The new plants may have nutritional __________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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components that favor these leafhoppers or they may produce poisons that prevent the reproduction of leafhoppers with other characteristics. 9. Identify some major sources of pesticides in your area. Examples: golf courses, parks, residential yards, farms, restaurants, grocery stores. 10. What happened to the proportions of leafhoppers in each subsequent generation when pesticides were added to the environment? Explain why all the leafhoppers were not killed by the pesticide application. The smaller brown leafhoppers are selectively killed by the pesticides. Larger black leafhoppers appear to be resistant to the pesticide applications; they probably possess genes that protect them from the pesticides. They may avoid the pesticide application with a behavioral adaptation or have metabolic traits that protect them from pesticide poisoning. This type of pesticide use would ultimately change the populations of the insects being sprayed and possibly lead to insects that tolerate pesticide applications.
__________________________________________________________________________________ __ Campbell/Reece/Simon Essential Biology 2e and Essential Biology with Physiology © Pearson Education
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