Pleodorina starrii has an incomplete division of labor. Although the 12 small cells near the top of this colony only swim, the 20 larger cells both swim and reproduce. (Credit: Copyright 2008 Matthew Herron)From Science Daily:
ScienceDaily (Feb. 22, 2009) — Some algae have been hanging together rather than going it alone much longer than previously thought, according to new research.
Ancestors of Volvox algae made the transition from being a single-celled organism to becoming a multicellular colony at least 200 million years ago, during the Triassic Period.
At that time, Earth was a hot-house world whose inhabitants included tree ferns, dinosaurs and early mammals. Previous estimates had suggested Volvox's ancestors arose only 50 million years ago.
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