Thermoregulation Concept 40.3-Homeostatic Process for Thermoregulation involve Form, Function, and Behavior Susan Chen AP Biology 1st Pd.

Overview Thermoregulation- the process by which animals maintain an internal temp. within a tolerable range Physiological processes are very sensitive to changes in body temp. Ex. Changes in enzyme-mediated reactions, and the membrane becomes more rigid or fluid as temp. rise or fall

Endothermy Endothermic describes animals warmed mostly by heat generated form metabolism. Ex. Birds and Mammals

Ectothermy Ectothermic describes animals that gain most of their heat form external sources. Ex. Amphibians, lizards, snakes, turtles, many fishes, and most invertebrates

Endotherms vs. Ectotherms Endothermy and ectothermy are NOT mutually exclusive modes of thermoregulation. Ex. A bird is mainly endothermic, but it may also warm itself in the sun on a cold morning, much as an ectothermic lizard does. Because their heat source is mainly environmental, ectotherms generally need to consume much LESS food than endotherms of equivalent size.

Variations in Body Temp. Poikilotherms- animals whose body temp. varies with its environment. Homeotherms- animals with a relatively constant body temp. There is NO FIXED relationship btw source of heat with stability of temp.

Variations in Body Temp. Continue Common Misconceptions: Ectotherms are "cold-blooded" and endotherms are "warm blooded" Ectotherms do NOT necessarily have low body temp. Ex. Many ectothermic lizards have higher body temp. than mammals when sitting in the sun. "Cold-blooded" and "warm-blooded" are MISLEADING and have been dropped from the scientific vocab.

Balancing Heat Loss and Gain Thermoregualation depends on an animal's ability to control the exchange of heat with its environment. An animal, like any other animal exchange heat by 4 physical processes: CONDUCTION, RADIATION, CONVECTION, EVAPORATION.

Balancing Heat Loss and Gain: Insulation Mammals and birds can reduce the flow of heat btw them and its environment with insulation. Sources of insulation: hair, feathers and fat

Balancing Heat Loss and Gain: Circulatory Adaptations Circulatory systems provide the major routes for heat flow btw. the interior and exterior of the body. Vasodilation- an increase in the diameter of superficial blood (hence heat) caused by relaxation of muscles of the vessel walls Vasoconstriction- reduces blood flow and heat transfer by decreasing the diameter of superficial vessels Birds and mammals reduce heat loss by countercurrent exchange.

Balancing Heat Loss and Gain: Circulatory Adaptations Cont.

Balancing Heat Loss and Gain: Evaporative Cooling and Behavioral Responses Panting, sweating, and bathing increase evaporation, which in turn, cools the body. BOTH ectotherms and endotherms adjust the rate of heat exchange with their environment by behavioral responses. -Ex. 1) Hibernation 2) Moving from the sun to the shade 3) Restricting activities to the night

Balancing Heat Loss and Gain: Metabolic Heat Production Heat production (THERMOGENSIS) is increased by muscle activity----------shivering and moving. NONSHIVERING THERMONGENSIS occurs when certain hormones cause the mitochondria to increase metabolic activity and produce heat instead of ATP. BROWN FAT in the neck and btw the shoulders is specialized for rapid heat production.

Balancing Heat Loss and Gain: Metabolic Heat Production Cont. SOME ectoderms can also generate heat through spasmodic muscle contraction suggesting that certain groups of dinosaurs could have been endothermic.

Acclimatizations in Thermoregulation Acclimatizations- temporary changes in response to external environment NOT to be confused with ADAPTATIONS, a process of change n a population brought about by natural selection acting over many generations. In birds and animals, acclimatizations to seasonal temperature changes often includes adjusting the amount of insulation. Ex. Growing a thicker coat of fur in winter and shedding it in the summer

Acclimatizations in Thermoregulation Cont. Acclimatizations in ectotherms often involve adjustments at cellular levels Ex. -Cell produce variant of enzymes w/same function but DIFFERENT optimal temp. -Proportions of saturated and unsaturated lipids in membrane change; unsaturated lipids help keep membrane more fluid at lower temp.

Physiological Mechanisms Regulation of body temp. in humans is brought about by a complex system based on feedback mechanism. Hypothalamus- brain region, where the sensors for thermoregulation are concentrated. A group of nerve cells functions as a thermostat.

Concept 44.1-Osmoregulation balances the uptake of water and solutes.

Overview Osmoregulation- the process by which animals control solute concentration and balance water gain and loss. Animals' surroundings presents severe osmoregulatory challenges. Ex. -Desert animals live an environment that can quickly deplete their body water -Marine animals also face potential problem of dehydration -Freshwater animals live in an environment that threatens to flood and dilute their body fluids

Osmosis ALL animals face the need for osmoregulation Osmosis is the movement of water across a selectively permeable membrane It occurs when 2 solutions seperated by a membrane differ in osmotic pressure, or OSMOLARITY (total solute concentration, expressed as molarity)

Osmotic Challenges All animals maintain water balance in 2 ways. They are either: Osmoconformers- isoosmotic with its surroundings Osmoregulators- controls with its internal osmolarity independent of that of its environment All osmoconformers are MARINE animals

Osmotic Challenges Continue Stenohaline describes MOST animals, whether osmoconformers of osmoregulators, that cannot tolerate substantial changes in external osmolarity. Euryhaline describes CERTAIN osmoconformers and osmoregulators that can survive large fluctuations in external osmolarity.

Osmotic Challenges in Marine Animals Most marine animals are osmoconformers------their osmolarity is the SAME as that of seawater. But they differ considerably in concentration of specific solutes. Marine bony fishes constantly lose water by osmosis.

Osmotic Challenges in Marine Animals Cont. They must balance water loss by drinking large amounts of water----they then use their gills and kidneys to rid themselves of salt. In gills, specialized CHLORIDE cells transport chloride ions (Cl- ) out and sodium ions (Na+) follow passively. Kidneys excreted excess calcium, magnesium, sulfate w/small loss of water.

Osmotic Challenges in Freshwater Animals Their problem is the opposite of marine animals. They have an osmolarity higher than that of their environment, so they gain water by osmosis and lose salt by diffusion. Some fishes such as Salmon, can do both.

Osmotic Challenges in Freshwater Animals Cont. Water balance is solved by almost drinking NO water and excreting large amounts of very dilute urine. Salt is replenished by eating at the same time. Chloride cells in gills actively transport Cl- into the body and Na+ follows.

Osmotic Challenges in Land Animals Water is lost through urine and feces, across skin, and from moist surface in gas exchange. Body coverings of most terrestrial animals help prevent dehydration. Ex. waxy layers of insect exoskeleton, shells of land snails, and the layers of dead, keratinized skin

Osmotic Challenges in Land Animals Cont. Many terrestial animals esp. desert animals are nocturnal, which reduces evaporative water loss. They can also maintain water balance by eating and drinking moist foods and by producing water metabolically through CELLULAR RESPIRATION.

Energetics of Osmoregulation There is an ENERY COST for maintaining osmolarity btw its body and the external environment. Osmoregulation uses ACTIVE TRANSPORT to maintain solute concentration. The energy cost for osmoregulation depends on 3 factors: How different an animal's osmolarity is form its surroundings How easily water and solutes can move across the animal's surface How much work is required to pump solutes across the membrane

Transport Epithelia in Osmoregulation Water balance and waste disposal depends on transport epithelia Tranpsort Epithelia- layers of specialized epithelial cells that regulate the solute movements for waster disposal and for tempering changes in body fluids.

Hope you paid attention Hope you paid attention. Have fun rereading the chapters 40 and 44 if you did not. NOTE: The Princeton Review for AP Biology does NOT go over Thermoregulation and Osmoregulation.

Review Questions Compare the mechanism of thermoregulaton with osmoregulation. What modes of heat exchange is involved in wind chill, when moving air feels colder than still air at the same temp.? Flowers differ in how much sunlight they absort. Why might this matter to a humming bird seeking nectar on a cold morning? The movement of salt from the surrounding water to the blood of a freshwater fish requires the expenditure of energy in the form of ATP. Why? Why aren't any freshwater animals osmoconformers?