A Short-Term Advantage for Syngamy in the Origin of Eukaryotic Sex: Effects of Cell Fusion on Cell Cycle Duration and Other Effects Related to the Duration of the Cell Cycle—Relationship between Cell Growth Curve and the Optimal Size of the Species, and Circadian Cell Cycle in Photosynthetic Unicellular Organisms

Figure 1

Eukaryotic cell cycle profiles in modeling studies (a) and studies measuring the individual growth of single cells in fission yeast (b) and (c). The first assumes a triangular profile; while in the second, a final plateau always appears with no growth or very limited growth. The profiles in (b) and (c) are taken from Baumgärtner and Tolić-Nørrelykke [68, page 4337] (six profiles with red tones measuring the parameter of length), from Neumann and Nurse [69, page 596] (one blue profile: cell volume) and from Buchwald and Sveiczer [71, page 5 and 6] (two green profiles: length). The horizontal and vertical scales have been modified to match the beginning and end of every cycle, to better show the presence of the plateau. In figure (c) they have also been arranged vertically. Cells of fission yeast are cylindrical, with a constant diameter, and grow by extending at the ends; therefore, cell length is a good measure of the size (volume and mass) of these cells [101].