Sponges (Chapter 26.2)

1. Sponges (Chapter 26.2) Please set up your notebook for Cornell Notes

2. Phylum Porifera pore bearers • Sponge characteristics • Sessile  spend entire adult life attached in a single place • Multicellular with a few specialized cells • Heterotrophic with no cell walls

3. Form and function • Body plan  asymmetrical • Large central cavity • Choanocytes cells that use flagella to move water through the sponge • Osculum large opening at the top of sponge where water exits • This movement of water allows a sponge to feed, respire, excrete and circulate

4. Other cell structures • Spicule  a spike shaped structure made of silica or calcium carbonate • Spicules are made by cells called archaeocytes • Sponges are filter feeders • Sift microscopic food from water and digest intracellularly • Sponges have no nervous tissue and cannot respond to changes in the environment • Some sponges do produce toxins to thwart predators

5. Reproduction • Sexual  sperm is released into the water and drawn into other sponges by the choanocytes • Fertilization is internal • Zygote develops into a larva that is free floating and carried by water currents until it settles and attaches to a surface

6. Asexual • Budding  a new individual grows on the body of the parent and detaches forming a separate organism • Gemmules a group of archaeocytes surrounded by spicules • Can withstand extreme temperatures and drought

7. Why are sponges important? • Provide habitats for marine animals • Form partnerships with algae and bacteria • Spicules can direct light for photosynthesis even in dim water