Lesson 27 - Thermoregulation & Osmoregulation

27: thermoregulation & osmoregulation Monday, April 1, 2024 12:56 PM comparing basal metabolic rates (BMR) • in mammals, elephants use more total energy than shrews • per kg, small mammals have higher metabolic rates than larger animals metabolism and body size • as an organism grows in volume, it does so at a higher rate than it grows in surface area • greater surface area, the greater the metabolic rate • larger animals have proportionally less surface area to support metabolic needs ○ as body size increases, total BMR increases due to increased overall consumption ○ mass-specific BMR decreases due to reduced surface area to • greater surface area, the greater the metabolic rate • larger animals have proportionally less surface area to support metabolic needs ○ as body size increases, total BMR increases due to increased overall consumption ○ mass-specific BMR decreases due to reduced surface area to volume ratio of tissues temperature regulation • ectotherms: ○ use external sources of energy to modify/control body temperature ○ move around in their environment (ex. going into the sun or hiding from it) ○ ex. reptiles, amphibians, ray-finned fish • endotherms: ○ rely on internal energy (metabolic heat) to modify/control body temperature • poikilotherms: ○ body temperature varies with the environment ○ ex. insects • homeotherms: ○ body temperature is relatively stable regardless of environment ○ ex. mammals we can combine terms to provide more specific information about how an organism thermoregulates. antarctic marine fish, which use behavior to regulate their body temperatures, live in an environment that is thermally stable (i.e., always the same temperature). these fish are best described as: a. homeothermic endotherm b. poikilothermic ectotherm c. homeothermic ectotherm ○ ectotherm because of behavior use ○ thermally stable in environment, which is also thermally stable d. poikilothermic endotherm thermoregulation: costs and benefits • ectotherms: ○ expend less energy to maintain temperature ○ inactive under poor environmental conditions thermoregulation: costs and benefits • ectotherms: ○ expend less energy to maintain temperature ○ inactive under poor environmental conditions ○ enzymes function under a range of internal conditions ○ costly to maintain multiple enzymes • endotherms: ○ expend a lot of energy to maintain temperature ○ remain active in spite of poor environmental conditions ○ enzymes optimized for near constant internal conditions ○ efficient to have optimized enzymes ○ more derived but not necessarily better how body temperature changes • evaporation is cooling only • convection, radiation, and conduction can be both heating and cooling • convection: any fluid when taking a hot shower, the primary mechanism that increases your body temperature is: a. conduction b. convection ○ water is flowing c. evaporation d. radiation body temperature is: a. conduction b. convection ○ water is flowing c. evaporation d. radiation managing heat loss and gain • cooling: ○ the conversion of liquid sweat to vapor results in heat loss, cooling the body ○ vasodilation increases heat transfer from the body to the environment § higher surface area exposed to the environment • warming: ○ fat and fur keep mammals warm ○ feathers keep birds warm ○ mammals raise fur and birds raise feathers when cold to trap warm air extreme temperatures • in extreme heat, most animals have behavioral strategies ○ ex. being more active at night, moving away from the sun • in extreme cold, most animals have behavioral strategies ○ ex. hibernating and highly reducing metabolic rate for several months (black bears) ○ ex. torpor - shorter hibernation; lasts a few hours (hummingbirds) ○ ex. stasis - freezing the outside of one's cells and having immeasurable activity, including low cardiovascular and respiratory activity (wood frogs) water balance • osmolarity ○ number of molecules of solute per liter solution • osmoconformers ○ have the same osmolarity as its environment • osmoregulators ○ controls osmolarity independently of its environment water balance in aquatic environments • isosmotic organism • osmoregulators ○ controls osmolarity independently of its environment water balance in aquatic environments • isosmotic organism ○ water in organism = water in environment ○ water and salts continuously diffuse § passive transport; concentration gradient ○ osmoconformer • hyperosmotic organism ○ water in organism < water in environment ○ water moves in, salts move out ○ osmoregulator • hypoosmotic organism ○ water in organism > water in environment ○ water moves out, salts move in ○ osmoregulator marine animals • many are hypoosmotic organisms ○ salts move in, water moves out • can become strongly dehydrated ○ compensate by drinking large amounts of seawater • regulators freshwater animals • many are hyperosmotic organisms ○ salts move out, water moves in • gain water by osmosis ○ excrete large amounts of highly dilute urine • regulatorss all sharks live in marine habitats and are osmoconformers, but they must maintain a low concentration of salt in their blood to maintain homeostatic conditions. which of the following mechanisms explains how sharks do this? a. sharks rely on passive diffusion of salt out of their bodies and back into the environment b. sharks use active transport to pump salt out of cells for excretion back into the environment ○ when salt levels reach a critical level, they are pumped out how sharks do this? a. sharks rely on passive diffusion of salt out of their bodies and back into the environment b. sharks use active transport to pump salt out of cells for excretion back into the environment ○ when salt levels reach a critical level, they are pumped out ○ conform until they cannot anymore c. sharks have specialized gills that physically block dissolved salt ions from entering the body d. sharks make large amounts of highly dilute urine to flush out salt in the body water balance on land • • • • animals obtain water through eating and drinking animals lose water through secretions and excretions water loss is a major challenge adaptations that animals have to prevent water loss in the move from water to land: ○ less permeable skin, scales, hair, etc. § most tetrapods ○ amniotic egg ○ no osmoconformers on land an animal that changes temperature with its environment is: a. a thermoconformer and a poikilotherm b. a thermoconformer and a homeotherm c. a thermoregulator and a poikilotherm d. a thermoregulator and a homeotherm an aquatic animal is observed excreting large amounts of water into its environment. we would describe this animal as _____ relative to its environment. a. an osmoconformer that is hyperosmotic b. an osmoconformer that is hypoosmotic c. an osmoregulator that is hyperosmotic ○ water passively moves into the body and needs to be actively secreted ○ salt is passively moving out of the body d. an osmoregulator that is hypoosmotic