C ONTROL OF THE I NTERNAL E NVIRONMENT Chapter 25

T HERMOREGULATION Maintenance of an internal temperature Life processes are temperature sensitive Stable internal temperature despite external fluctuations Endotherms use their metabolism Some reptiles, fish, and insects too Ectotherms gain heat from external sources Not mutually exclusive

H EAT E XCHANGE Conduction : molecules between 2 objects in direct contact Higher to lower temperature movement Convection : movement of air or liquid past an object Radiation : electromagnetic waves between 2 objects not in direct contact Evaporation : surface of a liquid losing molecules as a gas

A DAPTATIONS FOR T HERMOREGULATION Metabolic heat Hormonal boost or moving around to contract skeletal muscles, i.e shivering Insulation Hair, fur and feathers rise to trap insulating layer of air, goose bumps are vestigial remnant Blubber in aquatic birds and mammals Circulatory adaptations Change blood flow by constricting blood vessels to surfaces to conserve heat, dilation to dissipate Countercurrent heat exchange : adjacent vessels flow opposite directions Standing on ice, cold water across gills, and muscles Evaporative cooling Sweating and panting expose moisture to be removed with heat Behavioral response Migration, basking in sun when cold and damp areas when hot, bathing, and layered clothing

O SMOREGULATION Balancing uptake and loss of water and solutes Animal cells: net uptake = ? Net loss = ? Water follows solutes by osmosis Osmoconformers : no net gain or loss of water Marine invertebrates have body fluids of similar [solute] as seawater Osmoregulators : necessary to regulate to prevent changes Freshwater fish have higher [solute] than environment H 2 O gained and salt lost = doesn’t drink H 2 0, ions from food, and lots of dilute urine Saltwater fish have lower [solute] than environment H 2 O lost and salt gained = drinks salt H 2 O with salt out gills and little concentrated urine Land animals obtain H 2 O from food and drink while losing water through evaporation and excretion Exoskeleton, dead skin layers, egg shells, and amnitotic sac to prevent dehydration

D ISPOSAL OF W ASTES Metabolism produces toxic nitrogenous wastes that are removed by excretion Form of waste depends on habitat and evolution Ammonia too toxic to store, but diffuses in water Urea less toxic so can be stored, but costs energy and H 2 O loss to remove Uric acid insoluble in H 2 O so is semisolid Costs more energy, but conserves H 2 O

U RINARY S YSTEM Forms and excretes urine while regulating water and ion concentrations in body fluids Kidneys filter blood to extract filtrate which contains H2O, urea, glucose, AA’s, ions, and vitamins Filtrate is processed so valuable solutes not lost in urine Blood enters kidney through the renal arteries to be filtered and leaves via the renal veins What is the urine pathway from kidneys to outside?

T HE K IDNEYS Consist of renal cortex (outer) and renal medulla (inner) Nephrons are the functional units Start and end in cortex, part in medulla Bowman’s capsule encloses the glomerulus which filters the blood Nephron tubule has 3 parts Drains to collecting duct to join filtrate from other nephrons Capillary system in Bowman’s capsule and around tubule system

U RINARY S YSTEM P ROCESSING Filtration H2O and small molecules through capillary tube from glomerulus to nephron tubule Reabsorption Filtrate returns valuable solutes to blood (tubule capillaries) Secretion Excess ions, drugs, and toxic substances from blood transported into filtrate (tubule capillaries) Excretion Urine from kidneys to outside

B LOOD F ILTRATE TO U RINE NaCl enters interstitial fluid, bringing H 2 O with Excess H + secreted and HCO 3 - reabsorbed to maintain blood pH Toxins from liver into tubule system Loop of Henle facilitates H 2 O reclaimation ADH sets amount of H 2 O reabsorbtion Lots of H 2 O dilutes solutes so ADH down = less H 2 O retained Alcohol inhibits ADH release = excess H 2 O loss