1. Excretion Osmoregulation – Controlling Solutes and Water

3. Nitrogenous Waste Ammonia Ammonia HIGHLY Toxic HIGHLY Toxic Can’t be stored in Body Can’t be stored in Body Doesn’t take much energy to produce (good) Doesn’t take much energy to produce (good) Highly Soluble in Water Highly Soluble in Water Therefore, used by organisms with a lot of access to water. Therefore, used by organisms with a lot of access to water.

4. Nitrogenous Wastes Urea Urea Medium Toxicity Medium Toxicity Can be carried in body for short period of time Can be carried in body for short period of time Medium Solubility – Little water needed Medium Solubility – Little water needed Medium Amount of Energy used to produce this in the Liver Medium Amount of Energy used to produce this in the Liver Used by animals with medium access to water (short period of storage in body) Used by animals with medium access to water (short period of storage in body)

5. Nitrogenous Wastes Uric Acid Uric Acid Least Toxic Least Toxic Carried in Body for long periods of time Carried in Body for long periods of time Least Soluble in Water Least Soluble in Water Will precipitate out of water Will precipitate out of water Most energy used to produce Most energy used to produce Used by animals where water conservation is premium (land animals with shells) Used by animals where water conservation is premium (land animals with shells) Lots of Uric Acid produced in shell – white powder Lots of Uric Acid produced in shell – white powder

7. Comparative Excretion If Cells are in contact with environment, NO need for Excretory Structures If Cells are in contact with environment, NO need for Excretory Structures Protozoa – No (Diffusion – OK) Protozoa – No (Diffusion – OK) Hydra – NO (Diffusion – OK) Hydra – NO (Diffusion – OK) Planaria – 3 cell layers … See next slide Planaria – 3 cell layers … See next slide