The girdled lizards (Cordylidae) are a family of distinctively armored lizards endemic to
Sub-Saharan Africa. Students examine lizards in this family to classify the lizards based on
morphological characteristics. Students graph data on the percentage of osteoderm
coverage in each lizard group and discover that natural selection due to predation has
resulted in lightly armored lizards living in large rocks and more heavily armored lizards
living in open areas. Students then compare their morphological classification to
phylogenetic trees created from DNA analysis and discover that convergent evolution is
responsible for differences in ostederm coverage within the Cordylidae family and in the
Subject, Grade, Level:
This activity is targeted for AP Biology.
By the end of this activity, students will be able to:
1. Explain why molecular data provide more accurate and reliable evidence than
morphological traits when constructing phylogentic trees.
2. Differentiate between convergent and divergent evolution.
4 class periods (50-minute periods
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