Eartha Sherrill - Daniel Hale Williams School  



People Are Like Peas in a Pod 

Eartha Sherrill                Daniel Hale Williams School  
11337 South Normal Avenue      2710 South Dearborn Street
CHICAGO IL  60628              CHICAGO IL  60616 
                               (773) 534-9226 

Objective(s):

The objectives of these activities are:

        1.  To observe and appreciate the diversity of individuals
            within a population.

        2.  To promote student understanding of how dominant traits,
            recessive traits, genotypes, and phenotypes help produce
            variation in a population.

        3.  To demonstrate how to construct a Punnett Square.

These activities are designed for grades 5 - 8.

Materials Needed:

Activity One
        1 dozen intact fresh pea pods
        a roll of paper towels

Activity Two
    Enough materials for groups of two.
        styrofoam cups
        one-half cup of black-eyed peas
        plastic or metal tray
        metric ruler
        graph paper
        Science notebook

Activity Three
      2 pieces of 8-1/2" by 11" black or dark colored construction paper
        cut into 4 parts, each about 2 1/2" by 8 1/2"
      2 pieces of clear transparency film cut into four parts
           
Strategies:

Activity One
1.  Write the words population, species, and variation on the blackboard.
2.  One member from each group will obtain a pea pod.
3.  Have each group examine a pod to observe the variations in pea size.
    When students open the pods, they will notice that the peas near the
    center are larger.  Why?  Are the peas constricted?  This can lead to
    a discussion of heredity and environment.
4.  Relate the terms species, population, and variation to the pea pods.


Activity Two
1.  Have students form groups of two and have one member from each group 
    get the supplies.
2.  Point out that the cup of peas is the group's sample population
    and that they are looking for variations within that sample.
3.  Ask students to pour the peas onto the tray so they can see all the peas at 
    once.  Each group should look for ways the peas are similar or different. 
4.  Tell each group to choose three differences (variables) including one
    that can be measured with the ruler.
5.  Monitor the class as they decide which characteristics of peas they will 
    select.  Those who can't find any characteristics other than color, texture, 
    or size might need a little prodding.  Ask those students a question such 
    as, "What other differences do you see?" 
6.  Taking one variable at a time, students should sort their peas on the tray, 
    then write the variable and record the number of peas showing that 
    characteristic in their notebook. 
7.  Students will take the results for each variable and plot the number of peas 
    on the graph paper.  (A bar graph works well.)  Place a model on the 
    chalkboard as an example. 
8.  Have those students who finish the sorting, classifying, and plotting before 
    others, compute the data percentages and record them in their notebook.
9.  When the class has finished the assignment, have each group share their 
    results.  Write the results on the chalkboard and discuss the similarities 
    and differences between the findings of each group.  Some questions to 
    consider for discussion:  Why are some peas wrinkled or small?  Why are 
    there differences between samples? 

Activity Three
1.  Discuss and write the terms dominant trait, recessive trait, genotype,
    and phenotype on the blackboard.  Have students write the definition
    for each in their notebook.
2.  Place students in groups of two and have one member from each group get 
    the materials. 
3.  Explain to students that they have two pieces of dark construction paper
    and two pieces of clear plastic.  Say "The dark paper represents
    a dominant gene and the clear plastic represents a recessive gene."
    In the activity, use the words "dark" or "clear" to describe the phenotype
    and the letters "D" for dominant and "d" for recessive to describe the
    genotype.
4.  Write the following instructions on the chalkboard.
 
    Describe the genotype and phenotype.
        1.  Place one dark strip on top of the other dark strip.  Result?
        2.  Place one dark strip on top of one clear strip.  Result?
        3.  Place one clear strip on top of one dark strip.  Result?
        4.  Place one clear strip over the other clear strip.  Result?

5.  Discuss and demonstrate the results on a Punnett Square. Then show 
    students how to show inheritance through three generations.
6.  Provide students with a list of dominant genes in humans.  Working in
    pairs, students will select one human trait and demonstrate three 
    generations on a Punnett Square.
7.  Individual groups will write their results on the chalkboard.  Then
    each group will discuss the accuracy of their results.


Performance Assessment:

Students will write a paragraph explaining how inheritance of dominant and 
recessive genes helps produce variation in a population.

Conclusions:

Dominant and recessive genes can contribute to variation in a species.  
Variation is necessary for the survival of a species.

References: 

 Super Science Activities.  Palo Alto, CA: Dale Seymour Publications, 1988.