chapter 40 basic principles of animal form and...
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Chapter 40Basic Principlesof Animal Formand Function
Overview: Diverse Forms, CommonChallenges
Anatomy is the study of the biological form of anorganismPhysiology is the study of the biological functions anorganism performsThe comparative study of animals reveals that formand function are closely correlated
Concept 40.1Animal form and function arecorrelated at all levels oforganization
Size and shape affect the way an animalinteracts with its environmentMany different animal body plans have evolvedand are determined by the genome
Physical Constraints on Animal Sizeand Shape
The ability to performcertain actions depends
size, and environmentEvolutionaryconvergence reflects
adaptations to a similarenvironmentalchallengePhysical laws imposeconstraints on animalsize and shape
(a) Tuna
(b) Penguin
(c) Seal
Exchange with the Environment
exchanges energy and materials with itssurroundingsExchange occurs as substances dissolved in theaqueous medium diffuse and are transported
A single-celled protist living in water has a sufficientsurface area of plasma membrane to service itsentire volume of cytoplasmMulticellular organisms with a sac body plan havebody walls that are only two cells thick, facilitatingdiffusion of materials
Exchange
0.15 mm
(a) Single cell
1.5 mm
(b) Two layers of cells
Exchange
Exchange
Mouth
Gastrovascularcavity
More complex organisms have highly foldedinternal surfaces for exchanging materials
0.5 cmNutrients
Digestivesystem
Lining of small intestine
MouthFood
External environment
Animalbody
CO2 O2
Circulatorysystem
Heart
Respiratorysystem
Cells
Interstitialfluid
Excretorysystem
Anus
Unabsorbedmatter (feces)
Metabolic waste products(nitrogenous waste)
Kidney tubules
10 µm
Lung tissue
Exchange with the EnvironmentIn vertebrates, the space between cells is filled withinterstitial fluid, which allows for the movement ofmaterial into and out of cellsA complex body plan helps an animal in a variableenvironment to maintain a relatively stable internalenvironment
Hierarchical Organization of BodyPlans
Most animals are composed of specialized cellsorganized into tissues that have different functionsTissues make up organs, which together make uporgan systemsTissue Structure and FunctionDifferent tissues have different structures that aresuited to their functionsTissues are classified into four main categories:epithelial, connective, muscle, and nervous
Epithelial TissueEpithelial tissue covers the outside of the body andlines the organs and cavities within the bodyIt contains cells that are closely joinedThe shape of epithelial cells may be cuboidal (likedice), columnar (like bricks on end), or squamous(like floor tiles)The arrangement of epithelial cells may be simple(single cell layer), stratified (multiple tiers of cells), orpseudostratified (a single layer of cells of varyinglength)
Epithelial TissueCuboidalepithelium
Simplecolumnarepithelium
Pseudostratifiedciliatedcolumnarepithelium
Stratifiedsquamousepithelium
Simplesquamousepithelium
Apical surface
Basal surfaceBasal lamina
40 µm
Connective TissueConnective tissue mainly binds and supports other tissuesIt contains sparsely packed cells scattered throughoutan extracellular matrixThe matrix consists of fibers in a liquid, jellylike, or solidfoundationThere are three types of connective tissue fiber, all madeof protein:
Collagenous fibers provide strength and flexibilityElastic fibers stretch and snap back to their original lengthReticular fibers join connective tissue to adjacent tissues
Connective tissue contains cells, includingFibroblasts that secrete the protein of extracellular fibersMacrophages that are involved in the immune system
Connective TissueIn vertebrates, the fibers and foundation combineto form six major types of connective tissue:
Loose connective tissue binds epithelia to underlyingtissues and holds organs in placeCartilage is a strong and flexible support materialFibrous connective tissue is found in tendons, whichattach muscles to bones, and ligaments, whichconnect bones at jointsAdipose tissue stores fat for insulation and fuelBlood is composed of blood cells and cell fragments inblood plasmaBone is mineralized and forms the skeleton
Connective Tissue
Collagenous fiberLooseconnectivetissue
Elastic fiber
Cartilage
Chondrocytes
Chondroitinsulfate
Adiposetissue
Fat droplets
White blood cells
Plasma Red bloodcells
Blood
Nuclei
Fibrousconnectivetissue
OsteonBone
Central canal
Muscle TissueMuscle tissue consists of long cells called muscle fibers,which contract in response to nerve signalsIt is divided in the vertebrate body into three types:
Skeletal muscle, or striated muscle, is responsible forvoluntary movementSmooth muscle is responsible for involuntary body activitiesCardiac muscle is responsible for contraction of the heart
Muscle Tissue
50 µmSkeletalmuscle
MultiplenucleiMuscle fiberSarcomere
100 µm
Smoothmuscle
Cardiac muscle
Nucleus
Musclefibers
25 µm
Nucleus Intercalateddisk
Nervous TissueNervous tissue senses stimuli and transmits signalsthroughout the animalNervous tissue contains:
Neurons, or nerve cells, that transmit nerve impulsesGlial cells, or glia, that help nourish, insulate, andreplenish neurons
Glial cells
Nervous Tissue
15 µm
DendritesCell body
Axon
Neuron
Axons
Blood vessel
40 µm
Coordination and ControlControl and coordination within a bodydepend on the endocrine system andthe nervous systemThe endocrine system transmitschemical signals called hormones toreceptive cells throughout the body viabloodA hormone may affect one or moreregions throughout the bodyHormones are relatively slow acting, butcan have long-lasting effects
Stimulus
Hormone
Endocrinecell
Signal travelseverywherevia thebloodstream.
Bloodvessel
Response
(a) Signaling by hormones
Coordination and ControlThe nervous system transmits informationbetween specific locationsThe information conveyed depends on
signalNerve signal transmission is very fastNerve impulses can be received byneurons, muscle cells, and endocrinecells
Stimulus
Neuron
AxonSignal
Signal travelsalong axon toa specificlocation.
Signal
Axons
Response
(b) Signaling by neurons
Concept 40.2Feedback control loops maintainthe internal environment in manyanimals
Animals manage their internal environment byregulating or conforming to the externalenvironment
Regulating and ConformingA regulator usesinternal controlmechanisms tomoderate internalchange in the face ofexternal,environmentalfluctuationA conformer allows itsinternal condition tovary with certainexternal changes
River otter (temperature regulator)
Largemouth bass(temperature conformer)
0 10
10
20
20
30
30
40
40
Ambient (environmental) temperature (ºC)
HomeostasisOrganisms use homeostasis
environmentIn humans, body temperature, blood pH, andglucose concentration are each maintained at aconstant level
Mechanisms ofHomeostasis
Mechanisms ofhomeostasis moderatechanges in the internalenvironmentFor a given variable,fluctuations above orbelow a set point serve asa stimulus; these aredetected by a sensor andtrigger a responseThe response returns thevariable to the set point
Response:Heaterturnedoff
Stimulus:Control center(thermostat)reads too hot
Roomtemperaturedecreases
Setpoint:20ºC
Roomtemperature
increases
Stimulus:Control center(thermostat)
reads too cold
Response:Heaterturnedon
Feedback Loops in HomeostasisThe dynamic equilibrium of homeostasis ismaintained by negative feedback, which helps toreturn a variable to either a normal range or a setpointMost homeostatic control systems function bynegative feedback, where buildup of the endproduct shuts the system offPositive feedback loops occur in animals, but donot usually contribute to homeostasis
Alterations in HomeostasisSet points and normal ranges can change with ageor show cyclic variationHomeostasis can adjust to changes in externalenvironment, a process called acclimatization
Concept 40.3Homeostatic processes forthermoregulation involve form,function, and behaviour
Thermoregulation is the process by which animalsmaintain an internal temperature within atolerable range
Endothermy and EctothermyEndothermic animals generate heat by metabolism;birds and mammals are endothermsEctothermic animals gain heat from externalsources; ectotherms include most invertebrates,fishes, amphibians, and non-avian reptilesIn general, ectotherms tolerate greater variation ininternal temperature, while endotherms are activeat a greater range of external temperaturesEndothermy is more energetically expensive thanectothermy
Variation in Body TemperatureThe body temperature of a poikilotherm varies withits environment, while that of a homeotherm isrelatively constantOrganisms exchangeheat by four physicalprocesses: conduction,convection, radiation,and evaporation
Radiation Evaporation
Convection Conduction
Body Heat Loss and GainHeat regulation in mammals often involves theintegumentary system: skin, hair, and nailsFive general adaptations help animalsthermoregulate:
InsulationCirculatory adaptationsCooling by evaporative heat lossBehavioral responsesAdjusting metabolic heat production
ThermoregulationInsulation
Insulation is a major thermoregulatory adaptation inmammals and birdsSkin, feathers, fur, and blubber reduce heat flowbetween an animal and its environment
Circulatory AdaptationsRegulation of blood flow near the body surfacesignificantly affects thermoregulationMany endotherms and some ectotherms can alter theamount of blood flowing between the body core andthe skinIn vasodilation, blood flow in the skin increases,facilitating heat lossIn vasoconstriction, blood flow in the skin decreases,lowering heat loss
ThermoregulationCirculatory Adaptationscontinued
The arrangement of bloodvessels in many marinemammals and birds allowsfor countercurrentexchangeCountercurrent heatexchangers transfer heatbetween fluids flowing inopposite directionsCountercurrent heatexchangers are animportant mechanism forreducing heat loss
Canadagoose
Bottlenosedolphin
ArteryArtery
Vein VeinBlood flow
33º35ºC27º30º
18º20º
10º 9º
ThermoregulationCooling by Evaporative Heat Loss
Many types of animals lose heat through evaporation ofwater in sweatPanting increases the cooling effect in birds and manymammalsSweating or bathing moistens the skin, helping to cool ananimal down
Behavioural ResponseBoth endotherms and ectotherms usebehavioral responses to control bodytemperatureSome terrestrial invertebrates have posturesthat minimize or maximize absorption of solarheat
ThermoregulationAdjusting Metabolic Heat Production
Some animals can regulate body temperature byadjusting their rate of metabolic heat productionHeat production is increased by muscle activitysuch as moving or shiveringSome ectotherms can also shiver to increase bodytemperature
Contractions per minute0
0
20
2015105 25 30 35
40
60
80
100
120 PREFLIGHT PREFLIGHTWARM-UP
FLIGHTThorax
Abdomen
Time from onset of warm-up (min)0 2 4
25
30
35
40
Acclimatization in Thermoregulation
Birds and mammals can vary their insulation toacclimatize to seasonal temperature changesWhen temperatures are subzero, some ectotherms
formation in their cells
PhysiologicalThermostats andFever
Thermoregulation iscontrolled by a region ofthe brain called thehypothalamusThe hypothalamus triggersheat loss or heatgenerating mechanismsFever is the result of achange to the set point fora biological thermostat
Sweat glands secretesweat, which evaporates,cooling the body.
Thermostat inhypothalamusactivates coolingmechanisms.
Blood vesselsin skin dilate:capillaries fill;heat radiatesfrom skin. Increased body
temperature
Decreased bodytemperature
Thermostat inhypothalamusactivates warmingmechanisms.
Blood vessels in skinconstrict, reducingheat loss.
Skeletal muscles contract;shivering generates heat.
Body temperatureincreases; thermostat
shuts off warmingmechanisms.
Homeostasis:Internal temperature
of 36 38°C
Body temperaturedecreases;thermostat
shuts off coolingmechanisms.
Concept 40.4Energy requirements are related toanimal size, activity, andenvironment
Bioenergetics is the overall flow andtransformation of energy in an animalIt determines how much food an animal needs
environment
Energy Allocation and UseAnimals harvest chemicalenergy from foodEnergy-containingmolecules from food areusually used to make ATP,which powers cellularworkAfter the needs of stayingalive are met, remainingfood molecules can beused in biosynthesisBiosynthesis includes bodygrowth and repair,synthesis of storagematerial such as fat, andproduction of gametes
Organic moleculesin foodExternal
environmentAnimalbody Digestion and
absorption
Nutrient moleculesin body cells
Carbonskeletons
Cellularrespiration
ATP
HeatEnergy lostin feces
Energy lost innitrogenouswaste
Heat
Biosynthesis
Heat
Heat
Cellularwork
Metabolic Rate andThermoregulation
Metabolic rate is the amount of energy an animaluses in a unit of timeOne way to measure it is to determine the amountof oxygen consumed or carbon dioxide producedBasal metabolic rate (BMR) is the metabolic rate of
temperatureStandard metabolic rate (SMR) is the metabolic rateof an ectotherm at rest at a specific temperatureBoth rates assume a nongrowing, fasting, andnonstressed animalEctotherms have much lower metabolic rates thanendotherms of a comparable size
Influences on Metabolic RateMetabolic rates are affected by many factorsbesides whether an animal is an endotherm orectothermTwo of these factors are size and activity
Size andMetabolic Rate
Metabolic rate per gram isinversely related to bodysize among similar animalsResearchers continue tosearch for the causes ofthis relationshipThe higher metabolic rateof smaller animals leads toa higher oxygen deliveryrate, breathing rate, heartrate, and greater (relative)blood volume, comparedwith a larger animal
Elephant
Horse
HumanSheep
DogCat
RatGround squirrel
MouseHarvest mouse
Shrew
Body mass (kg) (log scale)10 3 10 2
10 2
10 1
10 1
10
10
1
1 102
102
103
103
(a) Relationship of BMR to body size
Shrew
Mouse
Harvest mouse
SheepRat Cat
DogHuman
HorseElephant
Ground squirrel
Body mass (kg) (log scale)10 3 10 2 10 1 1 10 102 103
0
1
2
3
4
5
6
8
7
(b) Relationship of BMR per kilogram of body mass to body size
Activity and Metabolic RateActivity greatly affects metabolic rate forendotherms and ectothermsIn general, the maximum metabolic rate an animalcan sustain is inversely related to the duration of theactivity
Energy BudgetsDifferent species use energy and materials in food indifferent ways, depending on their environmentUse of energy is partitioned to BMR (or SMR),activity, thermoregulation, growth, andreproduction
60-kg female humanfrom temperate climate
800,000Basal(standard)metabolism
ReproductionThermoregulation
Growth
Activity
340,000
4-kg male Adélie penguinfrom Antarctica (brooding)
4,000
0.025-kg female deer mousefrom temperateNorth America
8,000
4-kg female easternindigo snake
Endotherms Ectotherm
Torpor and Energy ConservationTorpor is a physiological state in which activity is lowand metabolism decreasesTorpor enables animals to save energy whileavoiding difficult and dangerous conditionsHibernation is long-term torpor that is an adaptationto winter cold and food scarcityEstivation, or summer torpor, enables animals tosurvive long periods of high temperatures andscarce water suppliesDaily torpor is exhibited by many small mammalsand birds and seems adapted to feeding patterns