Biology 1001A Lecture Notes - Lecture 16: Environmental Factor, Metaphase, Volvox

• School: Western University
• Department: Biology
• Course: Biology 1001A
• Professor: Tom Haffie

Document Summary

Likelihood that modern multi-cellular life forms are monophyletic. Not very likely at all; evidence shows that multicellularity has evolved multiple times over the course of evolution. Many branches on the tree of life (specifically eukarya) where some organisms are all unicellular, some are all multicellular, and others where species can be both. Characteristics of volvocine algae that make them a useful model system for studying the transition to multicellularity. Volvocine algae are a good model for multicellularity because they have both multicellular and unicellular species and have some who are intermediates. Also, the divergence of these species (chlamydomonas and volvox specifically) is very recent, occurring only 50 million years ago compared to the 1200 million years ago divergence between them and animals or land plants. Chlamydomonas is eukaryotic unicellular organism, has a single chloroplast, an eyespot, a couple mitochondria and flagella. It asexually divides and when it does, it loses its flagella.