Reproduction
Portuguese Man of Wars (men of war?) are a colony of genetically identical polyps. Each polyp is an individual organism in its own right, but is specialised to a certain role. They reproduce sexually using eggs and sperm, and then each offspring develops from a single organism by asexual reproduction so that the colony is a single genetic clone. As a result, the colony can reproduce successfully through just a few reproductive polyps.
This isn't all that different to yourself. There's no need for (say) your brain cells to produce sperm because the cells elsewhere can do it more efficiently with the same genetic relatedness. The difference is that your cells are organised into one large organism, whereas the Man of War has its cells divided into many organisms that are then organised into a larger colony that is analogous to a single organism.
www.aloha.com/~lifeguards/portugue.html for a little more...
(, Sun 28 Dec 2008, 17:31, Reply)