Methods
Habitats
Bibliography
Glossary
Schedule
Students

PHYCOLOGICAL SOCIETY OF AMERICA

Life History

Life Cycle       Fruiting Patterns       Swarmers       Phototaxis   

Vegetative Reproduction

Life Cycle

Click image to see a larger view of  Ulva's life history

All Ulva species are isomorphic, meaning that they alternate between gametophytic and sporophytic life stages with similar morphologies.  The gametophytes are haploid and the sporophytes are diploid.  The gametophytes produce biflagellate haploid gametes through mitosis, and the sporophytes produce quadriflagellate haploid zoospores through meiosis.  Ulva are slightly anisogamous, in that both gametes are motile and the female is a little bit larger.  

Vegetative cells                                  Reproductive cells

Reproductive activities occur near the margins of Ulva fronds, with the fertile portions turning slightly brown.  Both gametogenesis and sporogenesis are accompanied by a sharp reduction in photosynthetic capacity.  The motile reproductive cells all contain the ability to photosynthesize.

more life history