Homeostasis and Excretion

1. Homeostasis and Excretion • Chapter 44 Presentation by: Imani Phillips, Stephanie Riley, and Jamie Chavez

2. Osmoregulation and Excretion • Osmoregulation: how animals regulate solute concentrations and balance the gain and loss of water • Excretion: how animals get rid of the nitrogen-containing waste products of metabolism

3. Osmosis • Osmolarity: total solute concentration expressed as molarity or moles of solute per liter of solution • Unit of measurement: milliosmoles per liter(mosm/L) where 1 mosm/L = a total solute concentration of 10-3M • Osmolarity of human blood= 300 mosm/L while osmolarity of seawater= 1000 mosm/L • When tow solutions differ in osmolarity, • The one with greater concentration of solutes is hyperosmotic • The more dilute solution is hypoosmotic • When two solutions separated by a selectively permeable membrane have the same osmolarity they are said to be isoosmotic

4. 2 Basic Solutions to the Problem of Balancing Water Gain with Water Loss • Osmoconformers: • Available only to marine animals that mostly live in water that has a very stable composition • Does not actively adjust its internal osmolarity • Osmoregulators: • An animal that must control its internal osmolarity because its body fluids are not isoosmotic with the outside environment

5. Energy Cost of Osmoregulation • Osmoregulators must expend energy to maintain the osmotic gradients that cause water to move in or out • Energy Cost depends on • how different an animal’s osmolarity is from its environment • how easily water and solutes move across the animal’s surface • how much work is required to pump solutes across the membrane • Adaptations also help to reduce the energy cost by reducing the amount of water lost • ex: many animals that live in the desert are nocturnal. This reduces water loss by taking advantage of lower temperature and higher relative humidity of night air.

6. Transport Epithelia • Is a layer or layers of specialized epithelial cells that regulate solute movements • Moves specific solutes in controlled amounts in specific directions

7. Nitrogenous Wastes • When proteins and nucleic acids are broken apart for energy or converted to carbohydrates or fats, enzymes remove nitrogen in the form of ammonia which is very toxic • The amount of nitrogenous waste produced is tied to the energy budget because it strongly depends on how much and what kind of food the animal eats So Endotherms>Ectotherms in producing nitrogenous wastes So Predators>Herbivores in producing nitrogenous wastes

8. Forms of Nitrogenous Wastes