MuLTEERatcliff Lab · Georgia Tech

Outreach

Evolve your own multicellular yeast

We provide free laboratory kits and curricula for high school and college courses. Students can evolve multicellularity de novo using settling selection, or test the hypothesis that small-mouthed predators select for multicellular size. We have sent more than 100 kits worldwide.

Two labs

Lab 1: Experimental evolution · Lab 2: Predation

Animated microscopy: a Philodina rotifer consuming red-stained unicellular yeast while a blue-stained multicellular snowflake cluster sits untouched nearby.

Predation in action

Predator
Philodina rotifer
Red
Unicellular yeast (Congo red)
Blue
Multicellular yeast (methylene blue)
Lab 1

Evolve multicellular yeast

Duration
3 weeks (daily transfers)
Level
College, advanced high school
Core concept
Settling selection for larger size

Students culture unicellular S. cerevisiae Y55 and a previously evolved snowflake strain, perform daily settling selection for three weeks, and track evolved changes in cluster size and settling speed by microscopy. By selecting for faster or slower settling, students can drive evolution in opposite directions.

Ratcliff et al. 2014 · The American Biology Teacher 76:81–87

Lab 2

Predator-imposed selection for multicellularity

Duration
1–2 class periods (50 min each)
Level
High school and college
Core concept
Size-selective predation

Students feed differentially stained unicellular and multicellular yeast to Philodina rotifers, whose small mouths preferentially consume unicellular cells. Students count prey in the transparent rotifer stomachs and apply a chi-square test. Paramecium aurelia works as an alternative predator.

Pentz et al. 2015 · Evolution: Education and Outreach 8:13

Free kits

What is in the kit

The full kit: a ziploc bag of stained yeast and spore tubes, two boxes of glass cavity slides, a Falcon tube of YPD+Agar media, and a sterile multi-well culture dish.

The kit

NSF support allows us to provide kits free of charge. Each kit contains the key materials and reagents for the predation lab (Lab 2). Some supplies and equipment must be provided by the instructor.

Kit contents

  • 1 mL fixed, Congo red stained unicellular yeast
  • 1 mL fixed, methylene blue stained multicellular yeast
  • Unicellular yeast spores
  • Multicellular yeast spores
  • 6.5 g of YPD+Agar media (enough for 150 mL of culture media)
  • 10 glass concavity slides
  • 1 sterile multi-well culture dish (for plating yeast spores)

Supplied by the instructor

  • Compound microscopes
  • Transfer pipettes or micropipettes
  • Rotifers (Philodina sp., Carolina Biological Supply #133172) or Paramecium aurelia (#131546)

Request a kit

To order a kit, contact ratcliff@gatech.edu. Please allow about 6 weeks for delivery. Kits are provided free of charge with support from the National Science Foundation.

Curricula

Downloads

Lab 1 · Evolution

Student handout

The full student protocol for the 3-week settling-selection evolution lab.

Download PDF

Lab 1 · Evolution

Teacher guide

Preparation notes, scheduling suggestions, and answer keys.

Download PDF

Lab 1 · Evolution

Introductory presentation

Slides introducing multicellularity and the snowflake yeast system.

Download PPTX

Lab 2 · Predation

Student handout

The student protocol for the predation lab (1–2 class periods).

Download PDF

Lab 2 · Predation

Teacher guide

Preparation, rotifer care, and statistical analysis guidance.

Download PDF

Lab 2 · Predation

Introductory presentation

Slides on predation as a selective pressure for multicellularity.

Download PPTX

Both labs

Lab summary

Overview of both labs, materials, and learning objectives.

Download PDF

Assessment

Post-test

Assessment instrument for evaluating student learning outcomes.

Download PDF

All materials are free to use and modify for educational purposes.

Published curricula

The papers behind the labs

  1. Predator Escape: An Ecologically Realistic Scenario for the Evolutionary Origins of Multicellularity

    Jennifer T. Pentz, Tami Limberg, Nicholas Beermann, William C. Ratcliff

    2015 Evolution: Education and Outreach 8:13 doi.org/10.1186/s12052-015-0041-8

  2. A Novel Laboratory Activity for Teaching about the Evolution of Multicellularity

    William C. Ratcliff, Allison Raney, Sam Westreich, Sehoya Cotner

    2014 The American Biology Teacher 76:81–87 doi.org/10.1525/abt.2014.76.2.3

Acknowledgments

Contributors

These labs were created by Will Ratcliff with Tami Limberg (Great River High School), Nicholas Beermann (MacDowell Montessori High School), and Sehoya Cotner (University of Minnesota). Jennifer Pentz developed the predation lab. We are grateful to Michael Travisano, R. Ford Denison, Mark Borrello, Matthew Herron, Sam Westreich, and Allison Raney for discussions and improvements.

Supported by the National Science Foundation (DEB-1315147) and the Society for the Study of Evolution (2013 Thomas Henry Huxley Award for scientific outreach to Will Ratcliff).