Table 1.

Comparison of Chlamydomonas reinhardtii and Volvox carteri sexual cycles

Chlamydomonas reinhardtii	Volvox carteri
Nitrogen starvation is signal for gametogenesis	Diffusible sex inducer protein is signal for gametogenesis
Isogamous (equal sized gametes)	Oogamous (eggs and sperm)
All vegetative cells can differentiate into gametes directly	Eggs and sperm packets formed by only a subset of cells during sexual spheroid embryogenesis
Gametes can de-differentiate back to vegetative cells	Eggs can de-differentiate. Sperm are terminally differentiated
Gametes are free-swimming single cells that find each other by chance	Motile sperm packets must find a sexual female spheroid, gain entry, dissociate, and fertilize eggs
Zygotes undergo meiosis to form tetrads (all four products viable)	One large meiotic product survives; 3 small polar bodies are non-viable
Uniparental inheritance of chloroplast genome from MT+ parent and mitochondrial genome from MT− parent	Uniparental inheritance of both chloroplast and mitochondrial genomes from female parent