Development of multicellularity

Advantages of size Being big prevents others from eating you Being big allows you to eat others Change in ratio of surface area to volume as size increases. Metabolic rate is somewhat size dependent

Disadvantages of size Total energy requirements go up with increasing size In air and water, big causes more rapid sinking if not compensated for extensions of body or changes in specific gravity Diffusion becomes a problem

There must be an overall advantage Life as it evolved has become bigger (in bigger packages) Proximate and ultimate causes/effects

How does it happen Divisions Multinucleation Nuclear divisions--mitosis Cytoplasmic divisions--cytokinesis Multinucleation Syncitial--multinucleate, but no cell membranes. (fungi--saphrophytic/zoic Multicellularity--multiple mitoses and cytokineses

Cellular adhesion Glue--cell cement Physical structures

Advantages of multicellularity Increase size Division of labor Specialized cells

Disadvantages of multicellularity Total volume of food goes up Diffusion distances increase making the physical process of diffusion less functional

Volvocine method Volvox is a colonial algae Not much division of labor Hollow sphere with cells in outside layer colony

Protosponge approach Collar cells