Human Variation Investigation-Instruction Sheet and Discussion
Questions
Introduction: Variability is a basic characteristic of most species of living things.
Humans show variation in many visible traits. Some characteristics are inherited from
our parents; other characteristics are not inherited or can be influenced or determined by
the environment. For example, hair color is an inherited characteristic, but changing hair
color using dyes is not.
Some human traits have survival values, while others have no apparent survival value.
For example, having a long second toe does not mean life or death. But if a plant inherits
the lack of chlorophyll, it would die and not be able to reproduce.
Look at the individuals sitting around you. We are all members of the same species, but
are we all photocopies of one another?
Standards:
Genetics
2. A typical cell of any organism contains genetic instructions that specify its traits.
Those traits may be modified by environmental influences. As a basis for
understanding this concept:
b. Students know plant and animal cells contain many thousands of
different genes and typically have two copies of every gene. The two
copies (or alleles) of the gene may or may not be identical, and one
may be dominant in determining the phenotype while the other is
recessive.
Evolution
3. Biological evolution accounts for the diversity of species developed through
gradual processes over many generations. As a basis for understanding this
concept:
a. Students know both genetic variation and environmental factors are
causes of evolution and diversity of organisms.
Purpose: to examine variability among members of the class on the basis of a few
selected inherited traits.
Procedure:
1. Study the following table (figure 1). Working in pairs, determine both of
your characteristics for the 10 listed traits. Jot these characteristics down in
your lab report or journal.
2. Use the Wheel of Six Human Traits (figure 2). Start in the middle of the circle
with the first trait and determine whether it places you on the right or the left
side of the vertical line.
3. Move outward to the next circle and decide which of the 2 characteristics you
possess. Continue moving outward, trait by trait, until you come to the outer edge of
the wheel. Now read the number assigned to your particular combination of traits.
4. Record this number in your lab report or journal.
5. Have each class member write his or her number on the chalkboard.
6. Class Talley: Combine the numbers for all students in the class indicating where
there are multiple students for any particular number.
7. Construct a bar graph showing the class results.
Discussion:
1. Are there more non-tongue rollers or tongue rollers? What is the ratio of tongue
rollers to non-tongue rollers?
2. Are there traits that show up more in your class? What are these traits? Why do you
think that these traits are more common?
3. Is there anyone in the class like you with respect to all 6 traits? That is, does anyone
have the same assigned number you have?
4. If so, can you name a seventh trait that will distinguish between you? How will this
help?
5. If you had to keep extending the traits, how many more could you add?
6. In what ways would a person with number 1 be different from a person with number
64?
7. In what ways would a person with number 17 differ from one with number 45?
Conclusions:
Why are some traits more prevalent in a population even if there is little or no survival
value for these traits?
Key:
1. Students should come up with a ratio that approximates 3:1.
2. Students will not always come up with the idea of dominance. They may say some
traits are “stronger”.
3. Answers will vary.
4. Answers will vary, but they should be genetic traits not non-genetic traits.
It breaks the group down even further.
5. Thousands of traits can be observed in humans.
6. Individuals of numbers 1 and 64 will vary in all 6 traits.
7. Individuals of numbers 17 and 45 will differ in 4 traits: tongue rolling, hair texture,
ear lobes, and length of second toe.
8. Answers will vary, but students may be clustered due to dominant traits, gene
sampling of class, random chance, and the fact that only 6 traits outs of hundreds are
considered.
Conclusions:
Some traits are more prevalent in a population because of alleles that are dominant in
determining the phenotype.