BIOL 1361 1nd EditionExam # 3 Study Guide Lectures: 20 - 26Lecture 20 (November 20)Thermoregulation and Thermoconformity:- An animal is a regulator for an environmental variable if it uses internal mechanisms to control internal change in the face of external fluctuation. An example of this is a river otter.- An animal is a conformer for a particular variable if it allows its internal condition to change in accordance with external changes. An example of this is a bass.Behavior and Heat Exchange:- Endotherms, humans and birds, are warmed by heat generated by metabolism- Ectotherms, fish and reptiles and invertebrates, gain heat from external resourceso Ectotherms adjust their body temperature behaviorally by seeking out shade or laying in the suno Because their heat source is largely environmental, ectotherms generally consume less food than endotherms.Circulation and Heat Exchange:- In response to changing temperatures of their surroundings, many animals alter the amount of blood (and hence heat) flowing between their body core and their skin. - Nerve signals that relax the muscles of the vessel walls result in vasodilation, a wideningof superficial blood vessels.o As a result of the increase in vessel diameter, blood flow in the skin increaseso In endotherms, vasodilation usually warms the skin and increases the transfer of body heat to the environment by radiation, conduction and convection.- In contrast, vasoconstriction reduces blood flow and heat transfer by decreasing the diameter of superficial vesselsCounter Current Exchange:o In many birds and mammals, reducing heat loss from the body relies on countercurrent exchange, the transfer of heat between fluids that are flowing in opposite directionso In a countercurrent heat exchanger, arteries and veins are located adjacent to each others warm blood moves from the body core in the arteries, it transfers heat to the colder blood returning from the extremities in the veinso Because blood flows through the arteries and veins in opposite directions, heat is transferred along the entire length of the exchanger, maximizing the rate of heat exchange4 Components of An Animal’s Energy Budget:o Conduction The direct transfer of thermal motion (heat) between molecules of objects in contact with each other, as when a lizard sits on a hot rocko Convection The transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss from a lizards dry skin or when blood moves heat from the body core to the extremities Ex. fano Radiation The emission of electromagnetic waves by all objects warmer than absolute zero. A lizard absorbs heat radiating from the distant sun and radiates a smaller amount of energy to the surrounding air.o Evaporation The removal of heat from the surface of a liquid that is losing some of its molecules as gas. Evaporation of water from a lizards moist surfaces that are exposed to the environment has a strong cooling effect.Lecture 21 (November 12)Regulation of Blood [glucose]o Glucose absorbed across intestine into the bloodstreamo Blood glucose enters the liver and muscle cellso In the cells, glucose is polymerized to glycogeno The pancreas secretes insulin when blood glucose rises after eatingo The pancreas secretes glucagon when blood glucose drops below set point- First green arrow – eating- First black (thick) arrow – insulin release- Second black arrow – glucose uptake- Third black (thick) arrow – glucagon release- Fourth black arrow – glucose release and glycogen breakdownLecture 22 (November 17)Osmoregulation:- Controlling solute concentration and water gain or loss from the body fluids- Cell function requires specific and stable solute concentrationsExcretory Processes:- Filtrationo 2nd most selectively specifico The body fluid enters the epithelial tubule o Pressure is exerted hereo Only small molecules can cross the membrane- Reabsorptiono 1st most selectively specifico Selective recovery of valuable solutes Glucose Salts Vitamins Amino acids- Secretiono Also 1st most selectively specific o Selective transport of ions or other substances into filtrate- Excretiono 3rd most selectively specifico The filtrate leaves the bodyComparison of the Different Excretory Systems:Lecture 23 (November 19) 3 Structural Arrangements that Minimize Diffusion Distanceo Body shape Ex. a flattened, thin body will allow all cells to be within diffusion distanceof external environmento Gastrovascular Cavity In lacking a circulatory system, hydras and other cnidarians, a central Gastrovascular cavity functions in the distribution of substances throughout the body and in digestion.  The combination of a Gastrovascular cavity and a flat body is well suited for exchange with the environmento Circulatory System All cells are within diffusion distance of a capillary or sinusOpen Circulatory System versus Closed Circulatory System:o Open Circulatory System The lower hydrostatic pressures make them less costly in terms of energy expenditureo Closed Circulatory System High blood pressure enables the effective delivery of O2 and nutrients to the cells of larger and more active animals Well suited to regulating the distribution of blood to different organsArteries vs. Veins vs. Capillarieso Arteries (3 layers) Outer layer consists of THICKER connective tissue and elastin Middle layer consists of THICKER muscle and elastin Inner layer consists of endothelial cellso Veins (3 layers) Outer layer consists of THINNER connective tissue and elastin Middle layer consists of THINNERmuscle and elastin Inner layer consists of endothelial cells; valveo Capillaries (1 layer) 1 layer consists of endothelial cellsBlood Flow Rate and Pipe Diameter- The smaller the cross section, the faster the flow rate- The larger the cross section, the slower the flow rateSingle-Loop Circulation System vs. Double-Loop Circulation SystemLecture 24 (November 24)Similarities and Differences between Pathways of Local and Long Distance Signalingo Hormones The signaling molecules broadcast throughout the body by the endocrine system are called hormones Different hormones cause distinct effects, and only cells that have receptors for a particular hormone respond It takes many seconds for hormones to be released into the bloodstream and carried throughout the body The effects are long-lasting because the hormones can remain in the bloodstream