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18/04/12 Regula=ng and Conforming •  A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctua=on •  A conformer allows its internal condi=on to vary with certain external changes •  Animals may regulate some environmental variables while conforming to others © 2011 Pearson Education, Inc.
Figure 40.7
Homeostasis •  Organisms use homeostasis to maintain a steady state or internal balance regardless of external environment •  In humans, body temperature, blood pH, and glucose concentra=on are each maintained at a constant level © 2011 Pearson Education, Inc.
1 18/04/12 Mechanisms of Homeostasis •  Mechanisms of homeostasis moderate changes in the internal environment •  For a given variable, fluctua=ons above or below a set point serve as a s2mulus; these are detected by a sensor and trigger a response •  The response returns the variable to the set point Anima=on: Nega=ve Feedback Anima=on: Posi=ve Feedback © 2011 Pearson Education, Inc.
Figure 40.8
Feedback Control in Homeostasis •  The dynamic equilibrium of homeostasis is maintained by nega2ve feedback, which helps to return a variable to a normal range •  Most homeosta=c control systems func=on by nega=ve feedback, where buildup of the end product shuts the system off •  Posi2ve feedback amplifies a s=mulus and does not usually contribute to homeostasis in animals © 2011 Pearson Education, Inc.
2 18/04/12 Altera7ons in Homeostasis •  Set points and normal ranges can change with age or show cyclic varia=on •  In animals and plants, a circadian rhythm governs physiological changes that occur roughly every 24 hours © 2011 Pearson Education, Inc.
Figure 40.9
Figure 40.9a
3 18/04/12 Figure 40.9b
•  Homeostasis can adjust to changes in external environment, a process called acclima2za2on © 2011 Pearson Education, Inc.
Concept 40.3: Homeosta=c processes for thermoregula=on involve form, func=on, and behavior •  Thermoregula2on is the process by which animals maintain an internal temperature within a tolerable range © 2011 Pearson Education, Inc.
4 18/04/12 Endothermy and Ectothermy •  Endothermic animals generate heat by metabolism; birds and mammals are endotherms •  Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian rep=les © 2011 Pearson Education, Inc.
•  In general, ectotherms tolerate greater varia=on in internal temperature, while endotherms are ac=ve at a greater range of external temperatures •  Endothermy is more energe=cally expensive than ectothermy © 2011 Pearson Education, Inc.
Figure 40.10
5 18/04/12 Varia=on in Body Temperature •  The body temperature of a poikilotherm varies with its environment •  The body temperature of a homeotherm is rela=vely constant •  The rela=onship between heat source and body temperature is not fixed (that is, not all poikilotherms are ectotherms) © 2011 Pearson Education, Inc.
Balancing Heat Loss and Gain •  Organisms exchange heat by four physical processes: radia=on, evapora=on, convec=on, and conduc=on © 2011 Pearson Education, Inc.
Figure 40.11
6 18/04/12 •  Heat regula=on in mammals o`en involves the integumentary system: skin, hair, and nails •  Five adapta=ons help animals thermoregulate: –  Insula=on –  Circulatory adapta=ons –  Cooling by evapora=ve heat loss –  Behavioral responses –  Adjus=ng metabolic heat produc=on © 2011 Pearson Education, Inc.
Insula7on •  Insula=on is a major thermoregulatory adapta=on in mammals and birds •  Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment •  Insula=on is especially important in marine mammals such as whales and walruses © 2011 Pearson Education, Inc.
Circulatory Adapta7ons •  Regula=on of blood flow near the body surface significantly affects thermoregula=on •  Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin •  In vasodila=on, blood flow in the skin increases, facilita=ng heat loss •  In vasoconstric=on, blood flow in the skin decreases, lowering heat loss © 2011 Pearson Education, Inc.
7 18/04/12 •  The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange •  Countercurrent heat exchangers transfer heat between fluids flowing in opposite direc=ons and reduce heat loss © 2011 Pearson Education, Inc.
Figure 40.12
•  Some bony fishes and sharks also use countercurrent heat exchanges •  Many endothermic insects have countercurrent heat exchangers that help maintain a high temperature in the thorax © 2011 Pearson Education, Inc.
8 18/04/12 Cooling by Evapora7ve Heat Loss •  Many types of animals lose heat through evapora=on of water from their skin •  Pan=ng increases the cooling effect in birds and many mammals •  Swea=ng or bathing moistens the skin, helping to cool an animal down © 2011 Pearson Education, Inc.
Behavioral Responses •  Both endotherms and ectotherms use behavioral responses to control body temperature •  Some terrestrial invertebrates have postures that minimize or maximize absorp=on of solar heat © 2011 Pearson Education, Inc.
Figure 40.13
9 18/04/12 Adjus7ng Metabolic Heat Produc7on •  Thermogenesis is the adjustment of metabolic heat produc=on to maintain body temperature •  Thermogenesis is increased by muscle ac=vity such as moving or shivering •  Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic ac=vity •  Some ectotherms can also shiver to increase body temperature © 2011 Pearson Education, Inc.
Figure 40.14
Figure 40.15
10 18/04/12 Acclima=za=on in Thermoregula=on •  Birds and mammals can vary their insula=on to acclima=ze to seasonal temperature changes •  When temperatures are subzero, some ectotherms produce an=freeze compounds to prevent ice forma=on in their cells © 2011 Pearson Education, Inc.
Physiological Thermostats and Fever •  Thermoregula=on is controlled by a region of the brain called the hypothalamus •  The hypothalamus triggers heat loss or heat genera=ng mechanisms •  Fever is the result of a change to the set point for a biological thermostat © 2011 Pearson Education, Inc.
Figure 40.16
11 18/04/12 Figure 40.16a
Figure 40.16b
Concept 40.4: Energy requirements are related to animal size, ac=vity, and environment •  Bioenerge2cs is the overall flow and transforma=on of energy in an animal •  It determines how much food an animal needs and it relates to an animal s size, ac=vity, and environment © 2011 Pearson Education, Inc.
12 18/04/12 Energy Alloca=on and Use •  Animals harvest chemical energy from food •  Energy-­‐containing molecules from food are usually used to make ATP, which powers cellular work •  A`er the needs of staying alive are met, remaining food molecules can be used in biosynthesis •  Biosynthesis includes body growth and repair, synthesis of storage material such as fat, and produc=on of gametes © 2011 Pearson Education, Inc.
Figure 40.17
Quan=fying Energy Use •  Metabolic rate is the amount of energy an animal uses in a unit of =me •  Metabolic rate can be determined by –  An animal s heat loss –  The amount of oxygen consumed or carbon dioxide produced © 2011 Pearson Education, Inc.
13 18/04/12 Figure 40.18
Minimum Metabolic Rate and Thermoregula=on •  Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a comfortable temperature •  Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature •  Both rates assume a nongrowing, fas=ng, and nonstressed animal •  Ectotherms have much lower metabolic rates than endotherms of a comparable size © 2011 Pearson Education, Inc.
Influences on Metabolic Rate •  Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm •  Two of these factors are size and ac=vity © 2011 Pearson Education, Inc.
14 18/04/12 Size and Metabolic Rate •  Metabolic rate is propor=onal to body mass to the power of three quarters (m3/4) •  Smaller animals have higher metabolic rates per gram than larger animals •  The higher metabolic rate of smaller animals leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (rela=ve) blood volume, compared with a larger animal © 2011 Pearson Education, Inc.
Figure 40.19
Figure 40.19a
15 18/04/12 Figure 40.19b
Ac7vity and Metabolic Rate •  Ac=vity greatly affects metabolic rate for endotherms and ectotherms •  In general, the maximum metabolic rate an animal can sustain is inversely related to the dura=on of the ac=vity © 2011 Pearson Education, Inc.
Energy Budgets •  Different species use energy and materials in food in different ways, depending on their environment •  Use of energy is par==oned to BMR (or SMR), ac=vity, thermoregula=on, growth, and reproduc=on © 2011 Pearson Education, Inc.
16 18/04/12 Figure 40.20
Figure 40.20a
Figure 40.20b
17 18/04/12 Torpor and Energy Conserva=on •  Torpor is a physiological state in which ac=vity is low and metabolism decreases •  Torpor enables animals to save energy while avoiding difficult and dangerous condi=ons •  Hiberna2on is long-­‐term torpor that is an adapta=on to winter cold and food scarcity © 2011 Pearson Education, Inc.
Figure 40.21
•  Summer torpor, called es=va=on, enables animals to survive long periods of high temperatures and scarce water •  Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding paierns © 2011 Pearson Education, Inc.
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