Variation Within a Population (Evolution: How Change Occurs)
Teacher Worksheet
Standards:
 8b: Students know a great diversity of species increases the change that at least some organisms survive major
changes in the environment.
 8c: Students know the effects of genetic drift on the diversity of organisms in a population.
Duration:
This lab can be done in one period with questions as homework; spread over two days is recommended.
Objectives:
 Understand that there is variation within any given population.
 Understand that variation within a population can strengthen a species.
 Understand the mathematical concept of a mean.
Teacher Notes:
In Part A, the 10 maple leaves needed for each group should be taken from the same tree. In Parts A and B, it will be
necessary to provide tables on the board for students to tabulate total class counts. After the entire class has placed
measurements in the class tables, students can transfer the totals to the Data Tables in the laboratory investigation.
Questions/Answers:
Graphs: Answers will vary.
1. What is meant by the term variation? Small differences in appearance that organisms of the same species may
display.
2. In what length range are most of the kidney beans? Most of the leaf blades? Most of the petioles? Most samples
should fall in the middle ranges.
3. In what length range are the fewest beans? The fewest leaf blades? The fewest petioles? The fewest samples
should be at the extremes of the full-length range.
4. What is the general shape of each line graph? The shape of each graph should a bell or upside down U.
5. What do the shapes of the graphs indicate about the lengths of the kidney beans, the lengths of the leaf blades and
the lengths of the petioles? The shapes indicate that, although the lengths vary, most of the lengths are near the
average, with fewer samples at either extreme.
6. List two other variations that can be observed in the beans, leaf blades and petioles. Answers will vary, but might
include width, thickness, petiole diameter and/or coloration.
7. Are hand spans of all students in your class the same? No; lengths will vary, sometimes considerably.
8. Which hand span occurs most often? Least often? Answers will vary, but the results should be based on Data
Table 5 and Graph 3.
9. What is the general shape of the line graph? What does the shape of the line graph indicate about the hand spans
of the students in your class? The graph should look similar to Graphs 1 and 2, indicating that most human
measurements are near the average, with fewer measurements at both extremes.
Critical Thinking and Application
1. Why would having many seeds in a pod be a more useful adaptation to a bean plant than having only a few seeds?
The more seeds a pod has, the greater the possibility that some of them will germinate and grow into new bean
plants.
2. Why would having a very short root system be a harmful adaptation to a desert cactus plant? A cactus plant with
a short root system will have difficulty obtaining water. Thus, it will have difficulty surviving in the desert.
3. How is the white coat of certain arctic animals a helpful adaptation in the winter? The white coat color allows the
animals to blend in with their white surroundings. This enables these animals to hide from their predators
and/or sneak up on their own prey more successfully.
4. List two ways in which a large hand span might be a useful human adaptation. Answers will vary, but might
include the playing of musical instruments, increased athletic ability, carrying larger loads, survival against
predators, etc.