© William C. Ratcliff 2013 Rotifer Rotifers consume preferentially consume the red, unicellular yeast. Paramecium aurelia Paramecium preferentially consume the red, unicellular yeast. Lab 2: Predation An ecologically realistic scenario for the evolution of multicellularity Time: Four 50-minute classes Download Student handout     Download Teacher’s guide     Download Rotifer predation video     Download Rotifers for quantitation     Download Introductory powerpoint     The predators The first step in the transition to multicellularity is the evolution of cellular clusters. One major hypothesis is that small-mouthed predators could select for cluster formation, allowing clusters to escape predation. In this lab, students will examine the effects of rotifer predation on uni and multicellular yeast. The rotifers are fed both uni and multicellular yeast, which are labeled with either red or blue stains. Students microscopically examine rotifers consuming yeast, then flatten rotifers and examine the contents of their stomachs quantitatively. Using a chi squared test, they then determine if the rotifer preference for consuming unicellular yeast is statistically significant. This lab is highly modular, offering a range of opportunities for student and teacher involvement. For example, students can use yeast they evolved in Lab 1, or they can use yeast provided with the kit. Students can grow and stain their own yeast for this lab, or they can use stained yeast provided in the kit. We have also included an optional exercise using the unicellular ciliate predator, Paramecium aurelia. Please have your students complete these pre and post tests online. This assessment will provide critical data on this lab’s efficacy, and will help us improve the lab. These quizzes are quick and anonymous.