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Embryonic Development and Toxins


Jasmine D. Edgren
Department of Biology
North Carolina Wesleyan College
Erica F. Kosal
Department of Biology
North Carolina State University


This case study was written for an introductory course for biology majors who are first learning about embryonic development. The case is composed of several parts and involves a storyline about a team of researchers who find frogs and eggs in bamboo plants during a field study. Students consider what these observations mean, learn basics about the stages of animal embryonic development, and make connections to phylogeny and natural selection. Students then apply their understanding of animal embryonic stage development to the chemical atrazine in the environment by examining data from several experiments. As a concluding activity students write a letter to an agency or newspaper of their choosing stating their opinion surrounding the use of atrazine in the environment. The case proceeds in a progressive disclosure format and involves a combination of class discussion, small group work, and homework. Because the case focuses on very basic animal embryonic development, it would also be a great start to a developmental biology course or an embryology course.


  • Describe the basic stages of animal embryonic development.
  • Outline the basic pathways by which one stage of animal embryonic development might move into the following stage of development.
  • Explain the concepts of natural selection, selective pressures, as well as primitive and derived traits.
  • Evaluate graphs and data to understand embryonic development in a real situation in nature.
  • Critically think through phylogenetic comparisons of different species or different groups of animals and how their embryonic development might be the same or different from one another.


embryonic development; phylogeny; atrazine; frogs; bamboo; cleavage; cladogram; blastula; organogenesis; Xenopus laevis

Topical Areas

Ethics, Regulatory issues, Scientific argumentation

Educational Level

High school, Undergraduate lower division



Type / Methods

Directed, Discussion, Interrupted



Subject Headings

Biology (General)  |   Evolutionary Biology  |   Environmental Science  |   Zoology  |   Developmental Biology  |  

Date Posted


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