Grade Level

High School




Mara Laslo, Kaitlin Dinet

Lesson Summary

The purpose of this lesson is to provide an in depth exploration of homologies. Students will interpret phylogenetic trees, explore both structural and genetic homology, and apply what they’ve learned to make predictions about gene expression given phylogenetic relationships. Upon completion of this lesson, students will be able to:

  • understand that a “genetic toolkit,” a common set of developmental genes, is present in many species of mammals, and that differences in expression of these toolkit genes are largely responsible for differences among mammal forelimb structure;
  • explain how common genes present during limb development are evidence for evolution and common ancestry;
  • compare and contrast gene expression patterns within species across time and among species by making qualitative observations to explain how these expression patterns are evidence for evolution; and
  • analyze a phylogenetic tree to interpret relationships among species and to make predictions about when, relative to the evolution of given species, homologous traits and genes arose.


Science and Engineering Practices:

SP4, SP6

MA Science and Technology/Engineering (2016):


NGSS (2013):


Common Core Math/Language Arts Standards:



evidence of evolution, evolution, gene expression, homologous, tetrapod limbs

Educator SoundBites

"My students enjoyed this lesson and thought it was good because it made them think."
Jessica Ross, Midwood High School, Brooklyn, NY

Lesson Documents


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