Unit Plan 30 (Grade 7 Science): Embryological Evidence

Focus: Analyze embryological development to identify similarities and differences among species and use those patterns as evidence for relationships and change over time.

Grade Level: 7

Subject Area: Science (Life Science — Biological Evolution & Evidence)

Total Unit Duration: 5 sessions (one week), 50–60 minutes per session

I. Introduction

In this unit, students explore how embryos of different species can look surprisingly similar at early stages, then become more distinct as development continues. Using embryo image sets, developmental stage diagrams, and simple data tables, students analyze how features such as head shape, tail, limb buds, and gill slits/pharyngeal arches appear and change. They compare developmental sequences across species to identify patterns of similarity and difference and discuss how these patterns can be used as evidence of relatedness and evolutionary change. The unit culminates in an Embryological Evidence Explanation aligned with MS-LS4-3.

Essential Questions

• How can comparing embryos at different stages help scientists understand relationships among species?
• Why are embryos of different species sometimes more similar in early stages than the adults are?
• What kinds of similarities and differences in embryological development provide evidence for shared patterns or separate evolutionary paths?
• What are some limitations of using embryo images alone to draw conclusions about evolution?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Describe key features of embryonic development (e.g., head shape, tail, limb buds, eye spots, pharyngeal arches) in simple diagrams of multiple species.
2. Analyze displays of embryos at different stages to identify similarities and differences in early development among species.
3. Use tables and/or sorting activities to identify patterns in how embryos of related species are more similar at early stages and more different later.
4. Construct written or oral explanations that use embryological evidence to support ideas about relationships among species and patterns of change.
5. Create an Embryological Evidence Explanation (poster, one-pager, or slide) that clearly uses developmental comparisons among species, aligned with MS-LS4-3.

Standards Alignment — 7th Grade (NGSS-based custom)

• MS-LS4-3 — Analyze displays of embryological development of different organisms to identify similarities and differences among species and use these patterns as evidence of relatedness and evolution.
  • Example: Compare early embryo images of fish, amphibians, birds, and mammals and describe shared features and later differences.

Success Criteria — Student Language

• I can describe and label basic features in embryo diagrams from different species.
• I can use embryo image sets and tables to identify similarities and differences in development.
• I can notice patterns where embryos are more alike early and more different later, and explain what that might mean.
• I can write or present an explanation that uses embryological evidence to support a claim about relationships among species.
• I can mention at least one strength and one limitation of using embryo comparisons as evidence.