Choanoflagellates are unicellular protists but they also happen to be the closest living relatives to animals. This week, David Booth discusses what choanoflagellates are, where you can find them, and the connection to animal evolution. He also talks about how these microbes are interesting in their own right, impacting whole food webs and ecosytems and interacting with bacteria. We talk about the fossil record and cover a bunch of major evolutionary transitions and how microbial life was the precursor to the kingdoms of organisms we're most familiar with today.Dr. David Booth, PhD, is an assistant professor at University of California San Francisco. His lab investigates the ecological interactions and cell fate of choanoflagellates. You can follow him on Twitter (@dsboothacosta), Instagram (@bioboothlab) or find his work on his lab website or on Google Scholar.For more info on microbes and to follow updates of this podcast, find @couch_microscopy on Instagram, @CouchMicroscopy on Twitter, or visit www.couchmicroscopy.com/store for merch!Music is "Introducing Cosmic Space" by Elf Power and "Vorticella Dreams" by L. Felipe Benites.