1. Key Points From Last Lecture Homeostasis is made possible by physiological negative feedback loops Osmoregulation: Evolutionary trend towards greater control of osmoregulation, waste secretion

2. Outline/Key Points: Kidneys filter blood, regulate osmolarity (two functions) - Human kidneys - Concentration gradient/kidney function Water/salt needs of different animals are different - Too much water/too little salt - Too little water/too much salt

3. The Kidney Filters Wastes from Blood, and is the Effecter of Osmoregulation Fig 32_13

4. The Kidney performs two functions - osmoregulation and recovery of valuable materials Low salt concentration - No water crosses tubule High salt concentration - allows passive diffusion of water out of waste - birds and mammals Active recovery of valuable materials

5. The Kidney is an Effecter in a Negative Feedback Loop Allowing Osmoregulation Pg 626

6. Organisms Face Different Challenges to Osmoregulation Based on their Environment Fig 32_10 Either too little or too much water/salt Marine environments are analogous to deserts In freshwater environments salts and minerals are limited

7. Three Types of Nitrogenous Waste Fig 32_14 Type of waste and the amount of dilutions follows phylogeny

8. Too Much Water/Too Little Salt Bodies are saltier than environment = water moves in salt moves out Fig 32_8

9. Too Little Water/Too Much Salt Environment is saltier than body = water moves out salt moves in Fig 32_8

10. Additional Physiological Adaptations Involved in Osmoregulation Fig 32_9 Fig 32_12 Urea is deteoxified, used to raise osmolarity of blood which prevents water loss Salt in diet, specialized organ to eliminate salt Elasmobranch (marine) Marine bird