Paleobio Home Cassit Birds: Lessons on Genes, Inheritance,and Evolution
Lesson Two

Written by Jennifer A. Collins
Jen's Other Lessons   ~  Education
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Concept: The genotype and phenotype frequencies in a population can be measured.

Overview: Students use their understanding of genotype and phenotype to create their own Cassit bird by flipping pennies to represent genes. The class then shares the genotype and phenotypes of their birds so that a data table and graph can be started to show the frequency of the different genotypes and phenotypes.

Time:20-30 minutes

Grouping:individual, class

Vocabulary: phenotype, genotype, homozygous, heterozygous, allele

Advance Preparation: Make overheads, cut out Cassit Bird Sex Cells so that each student has one sex cell.


  • My Cassit Bird Female | My Cassit Bird Male
    (equal numbers of the male and female versions-1 per student)
  • Pennies (1 per student)
  • Colored pencils
  • Cassit Bird Data Table
  • Graph paper

    Procedure: 1.Explain to students that they are going to create a population of Cassit birds to learn how the gene frequencies and therefore phenotypes in a populations can change from generation to generation. They will only focus on beak shape, chest patches and sex.

    2.Pass out My Cassit Bird and penny to each student. Be sure that half of the class has female birds and the other half has male birds. Explain the information on the identification tag. Students will flip a coin to determine the genes of their bird and write this information along with the resulting phenotype onto the Cassit Identification tag.

    3.Students should color in the features of their bird according to the information on the Cassit Identification tag.

    4.Pass out a copy of the Cassit Bird Data Table and graph paper to each student. As a class, collect the data for the birds they just created. Inform students that this population is called the P or parent population. They will graph the class data as a bar graph, starting with this P generation. They will be adding data to both the data table and graph as new generations of birds are created.

    5.Review the population structure of the birds. Ask students to make prediction of what the next generations of birds might look like.

  • ©   Updated: June 2003   Contact: jen-AT-paleobio or allen-AT-paleobio