Embryology: Common Ancestry Lesson Plan

The goal of this exploratory lesson is to introduce students to one line of evidence that is used to understand the shared ancestry between different species. Students will compare and contrast the embryos of different species in order to study the shared similarities between those species. Students will use the evidence presented to them in order to construct an argument about the common ancestry between the embryos they are studying.




45 minutes

NGSS Standard

MS-LS4-3: Biological Evolution: Unity & Diversity


Embryo comparison worksheet

Activity Overview

  1. Explore student’s knowledge of embryos
  • Provide information on what an embryo is and how they develop over their gestational period
  • Explain how people study embryos and what we can learn by studying them
  1. Complete an embryo tables activity
  • Students will study embryos from different species at different stages of their development and attempt to organize and sort them by their species and developmental level
  • This activity demonstrates evidence of common ancestry as these embryos at their earlier stages look very similar to one another
  1. Open a guided discussion
  • Engage students to think about why the embryos at their early stages look so similar to one another
  • Construct an explanation and describe the evidence of common ancestry among living things

Teaching Guide

  1. Explore student’s knowledge of embryos
  • Begin the lesson by showing pictures of embryos of different species and ask students what they observe in the pictures. Ask them if they can guess what animals they are
  • Explain that these images show different embryos as they are growing and developing in gestation (from left to right: cat, chicken, iguana)
  • Tell students that people study embryos to learn how animals grow and develop over the course of their lives, and much can be learned by understanding how embryos grow
  1. Complete the embryo development activity, taken from North Arizona University
  • This activity will allow students to compare and contrast the embryonic development of different species through their gestation
  • Students should work together with a partner to complete the activity in this worksheet
  • Provide each pair with the worksheet provided 
    • Begin by reading the background section with a partner
    • Complete the activity by working through each stage of development to identify each species
    • The answers are provided on the last page of the activity. Instruct students not to look until they have finished making their guesses

Describe how what you learned from this activity supports the theory that all animals descended from a common ancestor.

  1. Open a guided discussion
  • When groups have finished working through the activity, open a discussion about their experiences and guesses
    • Ask them the following questions: was it difficult to identify the early stage embryos? The late stage embryos? Why or why not?
    • What do the similarities between the embryos tell you about the relationship between them?
    • Which animals do you think are the most closely related based on their embryos? The most distantly related? Why?

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