BI256 Lecture 7: Sponges and Radiate Animals
Document Summary
Lecture 7 sponges and radiate animals chapters 12 and 13. Cellular level of organization (different cell types performing different functions) Blastula stage but no germ layers or gut formation (all digestion is cellular) Assemblage of cells embedded in extracellular matrix with skeleton of spicules and protein. Approximately 15,000 species of sponges: marine environments, brackish waters, 150 in fresh water. Cladogram depicting evolutionary relationships among the four classes of sponges. Homoscleromorpha less than 100 species (small group), has true epithelium. Spongeocile inside empty space (only the red part that filters out food) Choanacytes lining (filter cells) (red parts on picture) Asconoids-flagelated spongocoels simplest, no folding in walls, small tube shaped. Wall fold to increase surface, choanocytes on internal canal. Leuconoids flagellated chambers increase in complexity = increase in size. Usually more than one osculum (oscula (plural)) Extensive canal system, evolved independently many times. Organized in gelatinous extracellular matrix: mesohyl sponge connective tissue. Thus, all fundamental processes occur at individual cell level.
