The microevolution lab provides a rare opportunity for students to address evolution and natural selection with a hands-on experiment that can be completed in less than two weeks. The experiment utilizes Pseudomonas fluorescens, a common, nonpathogenic saprophyte that colonizes soil, water and plant surface environments and Tetrahymena thermophila to demonstrate diversifying selection in response to predator-prey interaction. The basic lab can be expanded to compare resource competition and predation as driving forces behind adaptive radiation. Students observe predator-driven real time evolution in a micro-environment in about a week. In the presence of a Tetrahymena predator, clear phenotypic changes in bacterial growth pattern and niche formation are observed in liquid culture, and related changes in bacterial colony formation on agar plates are easily distinguished. Colony formation is dependent on what niche bacteria occupy in the liquid culture, e.g. surface biofilm compared to bottom dwellers.

Module Protocols

High School

Relevant Concepts

Mechanisms of Evolution; Population dynamics; Diversity of Organisms; Mutation; Prokaryotic and eukaryotic cells; Interdependence in Nature; Continuity and Change.

Next Generation Science Standards Relationships

High School: HS-LS1-3 | HS-LS2-6 | HS-LS3-2 | HS-LS4-1 | HS-LS4-2 | HS-LS4-3 | HS-LS4-4 | HS-LS4-5

Middle School: MS-LS1-1 | MS-LS1-5 | MS-LS2-4 | MS-LS2-5 | MS-LS3-1 | MS-LS4-4

NYS Science Curriculum Guideline Relationships

Key Ideas 1.1 | 1.2 | 1.3 | 4.1 | 4.2 | 4.3 | 4.6