Bài giảng Biology - Chapter 40: Basic Principles of Animal Form and Function

Chapter 40Basic Principles of Animal Form and FunctionOverview: Diverse Forms, Common ChallengesAnimals inhabit almost every part of the biosphereDespite their amazing diversityAll animals face a similar set of problems, including how to nourish themselvesThe comparative study of animalsReveals that form and function are closely correlatedFigure 40.1Natural selection can fit structure, anatomy, to function, physiologyBy selecting, over many generations, what works best among the available variations in a populationConcept 40.1: Physical laws and the environment constrain animal size and shapePhysical laws and the need to exchange materials with the environmentPlace certain limits on the range of animal formsPhysical Laws and Animal FormThe ability to perform certain actionsDepends on an animal’s shape and sizeEvolutionary convergenceReflects different species’ independent adaptation to a similar environmental challengeFigure 40.2a–e(a) Tuna(b) Shark(c) Penguin(d) Dolphin(e) SealExchange with the EnvironmentAn animal’s size and shapeHave a direct effect on how the animal exchanges energy and materials with its surroundingsExchange with the environment occurs as substances dissolved in the aqueous mediumDiffuse and are transported across the cells’ plasma membranesA single-celled protist living in waterHas a sufficient surface area of plasma membrane to service its entire volume of cytoplasmFigure 40.3aDiffusion(a) Single cellMulticellular organisms with a sac body planHave body walls that are only two cells thick, facilitating diffusion of materialsFigure 40.3bMouthGastrovascularcavityDiffusionDiffusion(b) Two cell layersOrganisms with more complex body plansHave highly folded internal surfaces specialized for exchanging materialsExternal environmentFoodCO2O2MouthAnimalbodyRespiratorysystemCirculatorysystemNutrientsExcretorysystemDigestivesystemHeartBloodCellsInterstitialfluidAnusUnabsorbedmatter (feces)Metabolic wasteproducts (urine)The lining of the small intestine, a diges-tive organ, is elaborated with fingerlikeprojections that expand the surface areafor nutrient absorption (cross-section, SEM).A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM).Inside a kidney is a mass of microscopic tubules that exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). 0.5 cm10 µm50 µmFigure 40.4Concept 40.2: Animal form and function are correlated at all levels of organizationAnimals are composed of cellsGroups of cells with a common structure and functionMake up tissuesDifferent tissues make up organsWhich together make up organ systemsDifferent types of tissuesHave different structures that are suited to their functionsTissues are classified into four main categoriesEpithelial, connective, muscle, and nervousTissue Structure and FunctionEpithelial TissueEpithelial tissueCovers the outside of the body and lines organs and cavities within the bodyContains cells that are closely joinedEpithelial tissueEPITHELIAL TISSUEColumnar epithelia, which have cells with relatively large cytoplasmic volumes, are often located where secretion or active absorption of substances is an important function.A stratified columnar epitheliumA simplecolumnar epitheliumA pseudostratifiedciliated columnarepitheliumStratified squamous epitheliaSimple squamous epitheliaCuboidal epitheliaBasement membrane40 µmFigure 40.5Connective TissueConnective tissueFunctions mainly to bind and support other tissuesContains sparsely packed cells scattered throughout an extracellular matrixCollagenousfiberElasticfiberChondrocytesChondroitinsulfateLoose connective tissueFibrous connective tissue100 µm100 µmNuclei30 µmBoneBloodCentralcanalOsteon700 µm55 µmRed blood cellsWhite blood cellPlasmaCartilageAdipose tissueFat droplets150 µmCONNECTIVE TISSUEConnective tissueFigure 40.5Muscle TissueMuscle tissueIs composed of long cells called muscle fibers capable of contracting in response to nerve signalsIs divided in the vertebrate body into three types: skeletal, cardiac, and smoothNervous TissueNervous tissueSenses stimuli and transmits signals throughout the animalMuscle and nervous tissueMUSCLE TISSUESkeletal muscle100 µmMultiplenucleiMuscle fiberSarcomereCardiac muscleNucleusIntercalateddisk50 µmSmooth muscleNucleusMusclefibers25 µmNERVOUS TISSUENeuronsProcessCell bodyNucleus50 µmFigure 40.5Organs and Organ SystemsIn all but the simplest animalsDifferent tissues are organized into organsLumen ofstomachMucosa. The mucosa is anepithelial layer that linesthe lumen.Submucosa. The submucosa isa matrix of connective tissuethat contains blood vesselsand nerves.Muscularis. The muscularis consistsmainly of smooth muscle tissue.0.2 mmSerosa. External to the muscularis is the serosa,a thin layer of connective and epithelial tissue.In some organsThe tissues are arranged in layersFigure 40.6Representing a level of organization higher than organsOrgan systems carry out the major body functions of most animalsOrgan systems in mammalsTable 40.1Concept 40.3: Animals use the chemical energy in food to sustain form and functionAll organisms require chemical energy forGrowth, repair, physiological processes, regulation, and reproductionThe flow of energy through an animal, its bioenergeticsUltimately limits the animal’s behavior, growth, and reproductionDetermines how much food it needsStudying an animal’s bioenergeticsTells us a great deal about the animal’s adaptationsBioenergeticsEnergy Sources and AllocationAnimals harvest chemical energyFrom the food they eatOnce food has been digested, the energy-containing molecules Are usually used to make ATP, which powers cellular workAfter the energetic needs of staying alive are metAny remaining molecules from food can be used in biosynthesisFigure 40.7Organic moleculesin foodDigestion andabsorptionNutrient moleculesin body cellsCellularrespirationBiosynthesis:growth,storage, andreproductionCellularworkHeatEnergylost infecesEnergylost inurineHeatHeatExternalenvironmentAnimalbodyHeatCarbonskeletonsATPAn animal’s metabolic rateIs the amount of energy an animal uses in a unit of timeCan be measured in a variety of waysQuantifying Energy UseOne way to measure metabolic rateIs to determine the amount of oxygen consumed or carbon dioxide produced by an organismFigure 40.8a, bThis photograph shows a ghost crab in arespirometer. Temperature is held constant in thechamber, with air of known O2 concentration flow-ing through. The crab’s metabolic rate is calculatedfrom the difference between the amount of O2entering and the amount of O2 leaving therespirometer. This crab is on a treadmill, runningat a constant speed as measurements are made.(a)(b) Similarly, the metabolic rate of a manfitted with a breathing apparatus isbeing monitored while he works outon a stationary bike.An animal’s metabolic rateIs closely related to its bioenergetic strategyBioenergetic StrategiesBirds and mammals are mainly endothermic, meaning thatTheir bodies are warmed mostly by heat generated by metabolismThey typically have higher metabolic ratesStem ElongationAmphibians and reptiles other than birds are ectothermic, meaning thatThey gain their heat mostly from external sourcesThey have lower metabolic ratesThe metabolic rates of animalsAre affected by many factorsInfluences on Metabolic RateSize and Metabolic RateMetabolic rate per gramIs inversely related to body size among similar animalsThe basal metabolic rate (BMR)Is the metabolic rate of an endotherm at restThe standard metabolic rate (SMR)Is the metabolic rate of an ectotherm at restFor both endotherms and ectothermsActivity has a large effect on metabolic rateActivity and Metabolic RateIn general, an animal’s maximum possible metabolic rateIs inversely related to the duration of the activityFigure 40.9Maximum metabolic rate(kcal/min; log scale)5001005010510.50.1AHAHAAAHHHA = 60-kg alligatorH = 60-kg human1second1minute1hourTime interval1day1weekKeyExisting intracellular ATPATP from glycolysisATP from aerobic respirationDifferent species of animalsUse the energy and materials in food in different ways, depending on their environmentEnergy BudgetsAn animal’s use of energyIs partitioned to BMR (or SMR), activity, homeostasis, growth, and reproductionEndothermsEctothermAnnual energy expenditure (kcal/yr)800,000BasalmetabolicrateReproductionTemperatureregulation costsGrowthActivitycosts60-kg female humanfrom temperate climateTotal annual energy expenditures (a)340,0004-kg male Adélie penguinfrom Antarctica (brooding)4,0000.025-kg female deer mousefrom temperateNorth America8,0004-kg female pythonfrom AustraliaEnergy expenditure per unit mass (kcal/kg•day)438Deer mouse233Adélie penguin36.5Human5.5PythonEnergy expenditures per unit mass (kcal/kg•day)(b)Figure 40.10a, bConcept 40.4: Animals regulate their internal environment within relatively narrow limitsThe internal environment of vertebratesIs called the interstitial fluid, and is very different from the external environmentHomeostasis is a balance between external changesAnd the animal’s internal control mechanisms that oppose the changesRegulating and conformingAre two extremes in how animals cope with environmental fluctuationsRegulating and ConformingAn animal is said to be a regulatorIf it uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuationAn animal is said to be a conformerIf it allows its internal condition to vary with certain external changesMechanisms of homeostasisModerate changes in the internal environmentMechanisms of HomeostasisA homeostatic control system has three functional componentsA receptor, a control center, and an effectorFigure 40.11ResponseNo heatproducedRoomtemperaturedecreasesHeaterturnedoffSet pointToohotSetpointControl center:thermostatRoomtemperatureincreasesHeaterturnedonToocoldResponseHeatproducedSetpointMost homeostatic control systems function by negative feedbackWhere buildup of the end product of the system shuts the system offA second type of homeostatic control system is positive feedbackWhich involves a change in some variable that triggers mechanisms that amplify the changeConcept 40.5: Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behaviorThermoregulationIs the process by which animals maintain an internal temperature within a tolerable rangeEctothermsInclude most invertebrates, fishes, amphibians, and non-bird reptilesEndothermsInclude birds and mammalsEctotherms and EndothermsIn general, ectothermsTolerate greater variation in internal temperature than endothermsFigure 40.12River otter (endotherm)Largemouth bass (ectotherm)Ambient (environmental) temperature (°C)Body temperature (°C)40302010102030400Endothermy is more energetically expensive than ectothermyBut buffers animals’ internal temperatures against external fluctuationsAnd enables the animals to maintain a high level of aerobic metabolismModes of Heat ExchangeOrganisms exchange heat by four physical processesRadiation is the emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that are not in direct contact, as when a lizard absorbs heat radiating from the sun.Evaporation is the removal of heat from the surface of aliquid that is losing some of its molecules as gas. Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect.Convection is the transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss from a lizard’s dry skin, or blood moves heat from the body core to the extremities.Conduction is the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other, as when a lizard sits on a hot rock.Figure 40.13Balancing Heat Loss and GainThermoregulation involves physiological and behavioral adjustmentsThat balance heat gain and lossInsulationInsulation, which is a major thermoregulatory adaptation in mammals and birdsReduces the flow of heat between an animal and its environmentMay include feathers, fur, or blubberHairSweatporeMuscleNerveSweatglandOil glandHair follicleBlood vesselsAdipose tissueHypodermisDermisEpidermisIn mammals, the integumentary systemActs as insulating materialFigure 40.14Many endotherms and some ectothermsCan alter the amount of blood flowing between the body core and the skinCirculatory AdaptationsIn vasodilationBlood flow in the skin increases, facilitating heat lossIn vasoconstrictionBlood flow in the skin decreases, lowering heat lossMany marine mammals and birdsHave arrangements of blood vessels called countercurrent heat exchangers that are important for reducing heat lossIn the flippers of a dolphin, each artery issurrounded by several veins in acountercurrent arrangement, allowingefficient heat exchange between arterialand venous blood.CanadagooseArteryVein35°CBlood flowVeinArtery30º20º10º33°27º18º9ºPacific bottlenose dolphin21323Arteries carrying warm blood down thelegs of a goose or the flippers of a dolphinare in close contact with veins conveyingcool blood in the opposite direction, backtoward the trunk of the body. Thisarrangement facilitates heat transferfrom arteries to veins (blackarrows) along the entire lengthof the blood vessels.1Near the end of the leg or flipper, wherearterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colderblood of an adjacent vein. The venous bloodcontinues to absorb heat as it passes warmer and warmer arterial blood traveling in the opposite direction. 2 As the venous blood approaches the center of the body, it is almost as warm as the body core, minimizing the heat lost as a result of supplying blood to body partsimmersed in cold water.3Figure 40.1513Some specialized bony fishes and sharksAlso possess countercurrent heat exchangersFigure 40.16a, b21º25º23º27º29º31ºBody cavitySkinArteryVeinCapillarynetwork withinmuscleDorsal aortaArtery andvein underthe skinHeartBloodvesselsin gills(a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintainstemperatures in its main swimming muscles that are much higherthan the surrounding water (colors indicate swimming muscles cutin transverse section). These temperatures were recorded for a tunain 19°C water. (b) Great white shark. Like the bluefin tuna, the great white sharkhas a countercurrent heat exchanger in its swimming muscles thatreduces the loss of metabolic heat. All bony fishes and sharks loseheat to the surrounding water when their blood passes through thegills. However, endothermic sharks have a small dorsal aorta, and as a result, relatively little cold blood from the gills goes directly to the core of the body. Instead, most of the blood leaving the gillsis conveyed via large arteries just under the skin, keeping cool bloodaway from the body core. As shown in the enlargement, smallarteries carrying cool blood inward from the large arteries under theskin are paralleled by small veins carrying warm blood outward fromthe inner body. This countercurrent flow retains heat in the muscles.Many endothermic insectsHave countercurrent heat exchangers that help maintain a high temperature in the thoraxFigure 40.17Cooling by Evaporative Heat LossMany types of animalsLose heat through the evaporation of water in sweatUse panting to cool their bodiesBathing moistens the skinWhich helps to cool an animal downFigure 40.18Both endotherms and ectothermsUse a variety of behavioral responses to control body temperatureBehavioral ResponsesSome terrestrial invertebratesHave certain postures that enable them to minimize or maximize their absorption of heat from the sunFigure 40.19Adjusting Metabolic Heat ProductionSome animals can regulate body temperatureBy adjusting their rate of metabolic heat productionMany species of flying insectsUse shivering to warm up before taking flightFigure 40.20PREFLIGHTPREFLIGHTWARMUPFLIGHTThoraxAbdomenTemperature (°C)Time from onset of warmup (min)40353025024Mammals regulate their body temperatureBy a complex negative feedback system that involves several organ systemsFeedback Mechanisms in ThermoregulationIn humans, a specific part of the brain, the hypothalamusContains a group of nerve cells that function as a thermostatThermostat inhypothalamusactivates coolingmechanisms.Sweat glands secrete sweat that evaporates, cooling the body.Blood vesselsin skin dilate:capillaries fillwith warm blood;heat radiates fromskin surface.Body temperaturedecreases;thermostatshuts off coolingmechanisms.Increased bodytemperature (suchas when exercisingor in hotsurroundings) Homeostasis:Internal body temperatureof approximately 36–38CBody temperatureincreases;thermostatshuts off warmingmechanisms.Decreased bodytemperature(such as whenin coldsurroundings)Blood vessels in skinconstrict, diverting bloodfrom skin to deeper tissuesand reducing heat lossfrom skin surface.Skeletal muscles rapidlycontract, causing shivering,which generates heat.Thermostat inhypothalamusactivateswarmingmechanisms.Figure 40.21Adjustment to Changing TemperaturesIn a process known as acclimatizationMany animals can adjust to a new range of environmental temperatures over a period of days or weeksAcclimatization may involve cellular adjustmentsOr in the case of birds and mammals, adjustments of insulation and metabolic heat productionTorpor and Energy ConservationTorporIs an adaptation that enables animals to save energy while avoiding difficult and dangerous conditionsIs a physiological state in which activity is low and metabolism decreasesHibernation is long-term torporThat is an adaptation to winter cold and food scarcity during which the animal’s body temperature declinesAdditional metabolism that would benecessary to stay active in winterActualmetabolismBodytemperatureArousalsOutsidetemperatureBurrowtemperatureJuneAugustOctoberDecemberFebruaryAprilTemperature (°C)Metabolic rate(kcal per day)200100035302520151050-5-10-15Figure 40.22Estivation, or summer torporEnables animals to survive long periods of high temperatures and scarce water suppliesDaily torporIs exhibited by many small mammals and birds and seems to be adapted to their feeding patterns