A Simple Transition to Multicellularity -- Not!

Volvox is a small spheroid green alga that lives in ponds, making its living by photosynthesis as plants do. Volvox is among the simplest animals to have more than one cell type. The hollow sphere that is its body is made up of somatic cells (soma is the Greek word for body). Within the sphere are specialized cells called gonidia (from the Greek gonē, meaning generation or seed). Early in embryogenesis, some cells divide to produce large cells. These become the gonidia, which then become emb...