VARIATIONS WITHIN A POPULATION LAB
Pre-Lab Discussion
The members of a species are not exactly alike. Small differences, called variations, exist in each
member of a species. Variations are found in all plants and animals. Some variations may be passed on to
the offspring of an organisms through reproduction. Most inherited variations are neutral; that is, they
do not affect the survival of the organism. Some variations are helpful. Helpful inherited variations are
called adaptations. Harmful inherited variations will cause the organism to be less well-suited to its
environment.
The process by which organisms with adaptations to the environment survive is called natural
selection. Natural selection tends to allow well-adapted organisms to reproduce and pass the beneficial
trait to their offspring. Organisms with harmful traits will die off. This process is sometimes referred
to as “survival of thefittest”
In this investigation, you will observe variations that exist in one type of plant as well as within
your classroom population.
Problem
How can the variations within plant and animal populations be measured?
Materials
10 kidney beans, metric ruler, colored pencils, graph paper
Part A. Variation Within a Species of Plants
1. Obtain a lab tray all your lab materials. This should have a cup with 10 kidney beans in it.
2. Measure the length of each kidney bean in millimeters. Record the measurements in Data Table 1
below.
3. When finished, report your measurements to the teacher. Your teacher wilt record all measurements
for the entire class and then dispiay the results en the overhead projector.
4. Copy the class results onto Data Table 2 below.
5. Using the data in Data Table 2, construct a bar graph for the kidney bean lengths on the top half of
a piece of graph paper. (See the board on how to construct the graph)
Part B. Variation within a species of Animal
1. Measure your handspan and that of your lab partner. Round off the measurement to the nearest
centimeter.
2. Record your hand span in Data Table 3 below. Then report your hand span to the teacher to record on
the class data table.
3. After all your classmate’s hand spans have been recorded on the class data table, transfer the class
results from the overhead projector to Data Table 4 below. Your results wiil show the total number of
hands having each different hand span.
4. Construct a bar graph of your hand span results using the same piece of paper as you used for the
kidney bean graph. (Use the bottom half of the same piece of graph paper).
Analysis and Conclusions
1. What is meant by the term variation?
2. What is meant by the phrase “survival of the fittest”?
3. In which range of lengths were most of the kidney beans?
4. In which range of lengths were the fewest number of kidney beans?
5. What is the general shape of the kidney bean graph?
6. What does the shape of the kidney bean graph indicate to you about the lengths of the kidney beans?
7. Are the hand spans of all students in your class the same?
8. Which hand span occurred most? least?
9. What is the general shape of the hand span graph?
10. What does the shape othe hand span ling graph indicate about the hand spans ofthe students in your
class?
Critical Thinking and Application
1. How does large seed size help a young plant to survive?
2. List two ways in which a large hand span might be a human adaptation for survival?
8)
b)
3. Why would having many seeds in a pod be a more adaptation to a bean plant than having only a few
seeds?
4. Why would having a very short root system be a harmful adaptation to a desert cactus plant?
5. How is the white coat color of certain arctic anirmals a helpful adaptation in the Winter?
6. Write a paragraph (at least 5 complete sentences) that describes the class results, explains why
there is variation and what might affect the variation (hint: why might each class have graphs that look
slightly different?).