Presentation on theme: "Chapter 40 Animal Form and Function"— Presentation transcript:
1Chapter 40 Animal Form and Function By: Pham Tran & Princess Montemayor
2Overview: Diverse Forms, Common Challenges Common set of problems: obtain oxygen, nourish themselves, excrete waste products and moveAnatomy is the study of the structure of an organismPhysiology is the study of the functions an organism performsNatural selection can fit structure to function
340.1 Physical laws and the environment constrain animal size and shape Size and shape, “body plans” or “designs,” affect the way an animal interacts with its environmentPhysical laws limit the evolution of an organism’s formConvergence evolution occurs because natural selection shapes similar adaptation when diverse organisms face the same environmental challenge
4Exchange with the Environment Size and shape also affect how an animal exchanges energy and materials with its surroundingsBody plan must allow all living cells to be bathed in an aqueous medium, a requirement for maintaining the fluid integrity of the plasma membranesExchange with the environment occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes
5Amoeba (unicellular protist), entire surface area is in contact with the environment.Hydra consists of two layers of cells with an aqueous environment circulating in and out of the hydra’s mouth, being directly in contact to every one of its cells – exchanging materials with it.
640.2 Animal form and function are correlated to all levels of organization Tissues are groups of cells with a common structure and functionClassified under four main categories:Epithelial tissueConnective tissueMuscle tissueNervous tissue
8Epithelial TissueEpithelial tissue covers the outside of the body and lines organs and cavities within the bodySome are tightly packed to function as a barrier against mechanical injury, microbes and fluid loss.Glandular epithelia absorb or secrete chemical solutions.Form a mucous membrane: secrete mucus that lubricates the surface and keeps it moist.
9(Epithelial tissue cont.) Simple epithelium has a single layer of cellsStratified epithelium has multiple tiers of cells.“Pseudostratified” epithelium is single-layered but appears stratified because the cells vary in length.Shape of the cells at exposed surface may be cuboidal, columnar, or squamous
10Connective TissueConnective tissue functions mainly to bind and support other tissues.Sparse population of cells scattered through an extracellular matrixTissue fibers made of protein:Collagenous fibersElastic fibersReticular fibers
11Connective tissue (cont.) Collagenous fibers are made of collagen, most abundant protein in animal kingdomNon-elastic, does not tear easilyEx. Skin on the back of handElastic fibers are long threads made of a protein called elastin.Rubbery quality that complements the nonelastic strength of collagenous fibers
12Connective tissue (cont.) Reticular fibers are very thin and branched.Composed of collagen and continuous with collagenous fibers to form a tightly woven fabric that joins connective tissue to adjacent tissuesFibroblasts secrete the protein ingredients of the extracellular fibers.Macrophages are amoeboid cells that roam the maze of fibers, engulfing foreign particles and the debris of dead cells by phagocytosis.
13Muscle TissueMuscle tissue is composed of long cells called muscle fibers that are capable of contracting, usually when stimulated by nerve signals.Myofibrils made of the proteins actin and myosin and serve as contracting units.Vertebrate body has three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle
14Nervous TissueNervous tissue senses stimuli and transmits signals in the form of nerve impulses from one part of the animal to another.Functional unit is the neuron or nerve cell, specialized to transmit nerve impulses.Most animals, nervous tissue is concentrated in the brain, the control center that coordinates the animal’s activity.
15Organ and Organ Systems Tissues are combined into functions called organs.Many of the organs of vertebrates are suspended by sheets of connective tissue called mesenteries in moist or fluid-filled body cavities.Mammals have a thoracic cavity housing the lungs and heart that is separated from the lower abdominal cavity by a sheet of muscle called the diaphragm.
16Organ and Organ Systems (cont.) Organ systems are groups of organs that work together to carry out the major body functions of most animals.Efforts of all systems must be coordinated for an animal to survive.
1740.3 Animals use the chemical energy in food to sustain form and function Bioenergetics limits an animal’s behavior, growth, and reproduction and determines how much food it needs.Food provides energy-containing molecules after digested, serves to generate ATPMetabolic rate – the amount of energy an animal uses over time; the sum of all the energy- requiring biochemical reactions occurring over a given time interval
19Bioenergetic Strategies Two basic strategies found in animals:Endothermic: bodies are warmed by heat generated by metabolismEctothermic: gain heat through external sourcesMetabolic rate is inversely related to size
2040.4: Many animals regulate their internal environment within relatively narrow limits Internal environment of vertebrates is called the interstitial fluid.Fluid fills spaces between vertebrate cells, exchanges nutrients and wastes with blood contained in microscopic vessels called capillariesAnimals tend to maintain relatively constant conditions in their internal environment, even when the external changesThere are times during development of an animal when major changes in internal environment are programmed to occur.Ex: The balance of hormones in human blood is altered radically during puberty and pregnancyHomeostasis: steady state or internal balanceA dynamic state, an interplay between outside factors that tend to change the internal environment and internal control mechanisms that oppose such changes
21Regulating and Conforming Regulating and conforming are two extremes in how animals cope with environmental fluctuationsAn animal is a regulator for a particular environmental variable if it uses internal control mechanisms to moderate internal change in the face of external fluctuationAn animal is a conformer for a particular environment variable if it allows its internal condition to vary with certain external changes.Regulating and conforming represent extremes on a continuum and no organism is a perfect regulator or conformer.An animal may maintain homeostasis while regulating some internal conditions and allowing others to conform to the environment
22Nonliving example of negative feedback : control of room temperature
23Mechanisms of Homeostasis Mechanism of homeostasis moderate changes in the internal environment.Any homeostatic control system has three functional components:(1) Receptor: detects change in some variable of the animals internal environment, such as a change in body temperature(2) Control Center: processes information it receives from the receptor and directs an appropriate response by the (3) effector.Example: Regulation of Room TemperatureIn this case, the control center, a thermostat, contained the receptor, which is a thermometer. When the room temperature falls below a set point, the thermostat switches on the heater, the effector. When the thermometer detects a temperature above the set point, the thermostat switches the heater off. This type of control is called negative feedback, because a change in the variable being monitored triggers the control mechanism to counteract further change in the same directionOwing to a time lag between reception and response, the variable drifts slightly above and below the set point, but the fluctuations are moderateNegative-feedback mechanisms prevent small changes from becoming too large; most homeostatic mechanisms in animals operate on this principle of negative feedback.Positive feedback involves a change in some variable that triggers mechanism that amplify rather than reverse the change.Regulated change is essential to normal body functionsOver the short term, homeostatic mechanisms keep body temperature close to a set point, whatever it is at that particular time, but long term, it allows regulated change in the body’s internal environmentAnimals use a considerable amount of energy from eaten food to maintain favorable internal conditions
2440.5: Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior Thermoregulation: the process by which animals maintain an internal temperature within a tolerable rangeCritical to survival because most biochemical and physiological processes are sensitive to changes in body temperature.Although different animals adapt to different environment temperatures, each has an optimal temperature rangeThermoregulation helps keep the body temperature within that optimal range, enabling cells to function most effectively, even as the external temperature fluctuates
25Ectotherms and Endotherms One way to classify thermal characteristics of animals is to emphasize the role of metabolic heat in determining body temperatureEctotherms (invertebrates, fishes, amphibians, lizards, snakes, turtles) gain most of their heat from the environment. They have such a low metabolic rate that the amount of heat generated is too small to affect their body temperatureTolerate greater variation in internal temperature than endothermsEndotherms ( Mammals, birds, some reptiles and fish, and insects) can use metabolic heat to regulate their body temperature; in cold temperatures, they generate enough heat to keep their bodies warmer than their surroundings.Many maintain high and stable internal temperatures even as the temperature of their surroundings fluctuates.Animals not classified as ectotherms or endotherms based on whether they have variable or constant body temperatures, a common misconception.It’s the source of heat used to maintain body temperature that distinguishes ectotherms from endotherms.Another misconception is that ectotherms are “cold-blooded” and endotherms are “warm-blooded”Ectotherms don’t necessarily have low body temperaturesEctothermy and endothermy aren’t mutually exclusive thermoregulatory strategies.Endothermy has several important advantagesBeing able to generate a large amount of heat metabolically, along with other biochemical and physiological adaptations associated with endothermy enables endotherms to perform vigorous activity for much longer than is possible for most ectotherms.Enables terrestrial animals to maintain stable body temperatures in the face of environmental temperature fluctuations that are generally more severe than in aquatic habitats.Better buffered against external temperature fluctuations compared to ectotherms, but ectotherms can tolerate larger fluctuations in their internal temperatures.Endotherms need to consume more food than ectotherms because being endothermic is energetically expensive
26Modes of Heat ExchangeRegardless if it’s an ectotherm or endotherm, an organism exchanges eat by four physical processes:Conduction: direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other, as when a lizard sits on a hot rockConvection: 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 blood moves heat from the body core to the extremitiesRadiation: emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that aren’t in direct contact, as when a lizard absorbs heat radiating from the sunEvaporation: removal of heat from the surface of a liquid that is losing some of its molecules as fast. Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect.
27Balancing Heat Loss and Gain For endotherms, and ectotherms that thermoregulate, the essence of thermoregulation is managing the heat budget so that rates of heat gain are equal to rates of heat lossIf heat budget is unbalanced, the animal becomes either warmer or colderFive general categories of adaptations help animals thermoregulateInsulationCirculatory AdaptationsCooling by Evaporative Heat LossBehavioral ResponsesAdjusting Metabolic Heat Production
28InsulationA major thermoregulatory adaptation in mammals and birds that reduces the flow of heat between an animal and its environment and lowers energy cost of keeping warmIn mammals, insulating material is associated with integumentary system, the outer covering of the body, consisting of the skin, hair, and nailsSkin functions as a thermoregulatory organ by housing nerves, sweat glands, blood vessels, and hair follicles and protects internal body parts from mechanical injury, infection, and drying out.Consists of two layers, the epidermis and the dermis, underlain by a tissue layer called the hypodermisEpidermis is the outermost layer of skin and is composed mostly of dead epithelial cells that continually flake and fall off. New cells pushing up from lower layers replace the cells that are lost.Dermis supports epidermis and contains hair follicles, oil and sweat glands, muscles, nerves, and blood vessels.Hypodermis contains adipose tissue, which includes fat-storing cells and blood vessels. Adipose tissue provides varying degrees of insulation, depending on the species.Insulating power of fur or feathers mainly depends on how much still air the layer traps
30Circulatory Adaptations Many endotherms and ectotherms can alter amount of blood (and hence heat) flowing between the body core and the skinElevated blood flow in the skin results from vasodilation, an increase in the diameter of superficial blood vessels triggered by nerve signals that relax the muscle of the vessel walls.in endotherms, vasolidation usually warms the skin, increasing the transfer of body heat to a cool environment by radiation, conduction, and convection.Vasoconstriction: reduces blood flow and heat transfer by decreasing the diameter of superficial vesselsCountercurrent heat exchanger: important for reducing heat loss in may endotherms, including marine animals and birds.In some species, blood can go either through the heat exchanger or bypass it by way of blood vessels. In this way, relative amount of blood that flows through the two paths may vary, adjusting the rate of heat loss as an animal’s physiological state or environment changes.
32Cooling by Evaporative Heat Loss Many Mammals and birds live in places where thermoregulation requires cooling as well as warmingIf environmental temperature is above body temperature, animals gain heat from the environment and metabolism, and evaporation is the only way to keep body temperature from rising rapidly.Terrestrial animals lose water by evaporation across the skin and when they breathe. Water absorbs considerable heat when it evaporates; this heat is carried away from the body surface with the water vaporSome animals have adaptations that can greatly augment this cooling effect like pantingMany terrestrial mammals have sweat glands controlled by the nervous systemOther mechanisms that promote evaporative cooling include spreading saliva on body surfaces, or secreting mucus
33Behavioral ResponsesBoth endotherms and ectotherms use behavioral responses to control body temperature.Many ectotherms maintain a nearly constant body temperature through simple behaviors. More complex behavioral adaptations in some animals include hibernation or migrationAll amphibians and most reptiles other than birds are endothermic which means these organisms control body temperature mainly by behaviorOptimal temperature range for amphibians varies substantially with the speciesBy moving to a location where solar heat is available, an amphibian can maintain a satisfactory body temperature and when it’s hot, they move to a cooler area
34Adjusting Metabolic Heat Production Because endotherms generally maintain body temperatures considerably warmer than the environment, they must counteract constant heat lossEndotherms can vary heat production to match changing rates of heat loss; heat production is increased by such muscle activity as moving or shiveringIn some mammals, certain hormones can cause mitochondria to increase their metabolic activity and produce heat instead of ATP. This nonshivering thermogenesis (NST) takes place throughout the body, but some mammals also have a tissue called brown fat in the neck and between the shoulders that is specialized for rapid heat production.Through shivering and NST, mammals and birds in cold environments can increase their metabolic heat production by as much as five to ten times the minimal levels that occur in warm conditions.
35Feedback Mechanisms in Thermoregulation Regulation of body temperature in humans and other mammals is a complex system facilitated by feedback mechanismsNerve cells that control thermoregulation, as well as those that control many other aspects of homeostasis, are concentrated in a region of the brain called the hypothalamusHypothalamus contains group of nerve cells that functions as a thermostat, responding to changes in body temperature above or below a set point by activating mechanisms that promote heat loss or gainNerve cells that sense temperature are in the skin, hypothalamus, and several other body regionsWarm receptors signal the hypothalamic thermostat when temperatures when temperatures increase; cold receptors signal temperature decrease. At body temperatures below the normal range, the thermostat inhibits heat loss mechanisms and activates heat-saving ones such as vasoconstriction of superficial vessels and erection of fur, while stimulating heat-generating mechanismsIn response to elevated body temperature, the thermostat shuts down heat retention mechanisms and promotes body cooling by vasolidation, sweating, or panting. The thermostat can also respond to external temperature even without changes in body core temperature
36Adjustment to Changing Temperatures Many animals can adjust to a new range of environmental temperatures over a period of days or weeks, a physiological response called acclimatizationBoth ectotherms and endotherms acclimatize, but in different ways. In birds and mammals, acclimatization includes adjusting amount of insulation by growing or shedding furHelps endotherms keep constant body temperature in warm and cold seasonsAcclimatization responses in ectotherms often include adjustments at the cellular level. Cells may increase certain enzymes or produce variants of enzymes that have the same function but different optimal temperatures.Membranes may also change proportions of saturated and unsaturated lipids they contain, which helps keep membranes fluid at different temperaturesSome ectotherms protect themselves by producing “antifreeze” compounds that prevent ice formation in the cellsCells can often make rapid adjustments to temperature changes. Mammalian cells respond to a marked increase in temperature and to other forms of severe stress by accumulating molecules called stress-induced proteins, including heat shock proteinsWithin minutes of being shocked, the cells begin synthesizing heat-shock proteins to help maintain the integrity of other proteins that would be denatured by severe heatStress induced proteins help prevent cell death when an organism is challenged by severe changes in the cellular environment
37Torpor and Energy Conservation Despite their many adaptations for homeostasis, animals may occasionally encounter conditions that severely challenge their abilities to balance heat, energy, and materials budgets.An adaptation that enables animals to save energy while avoiding difficult and dangerous conditions is torpor, a physiological state in which activity is low and metabolism decreasesHibernation: long-term torpor that is an adaptation to winter cold and food scarcity.When vertebrate endotherms enter torpor or hibernation, their body temperatures decline-in effect, their body’s thermostat is turned downResulting energy savings due to lower metabolic rate and less heat production are huge; metabolic rates during hibernation can be several hundred times lower than if the animal attempted to maintain normal body temperaturesThis allows hibernators to survive very long periods on limited supplies of energy stored in the body tissues or as food cached in a burrowEstivation, or summer torpor, also characterized by slow metabolism and inactivity enables animals to survive long periods of high temperatures and scarce water supplies.Many small mammals and birds exhibit a daily torpor that seems to be adapted to their feeding patternsAn animals daily cycle of activity and torpor appears to be a built-in rhythm controlled by its biological clock
38BibliographyCampbell, Neil A., and Jane B. Reece. Biology. AP ed. Vol. 7th. San Francisco: Pearson Education, Print.E., Marino F. Thermoregulation and Human Performance. NSW: Bathurst, Print."Homeostasis." - Definition from Biology-Online.org. Web. 07 Mar<http://www.biology-online.org/dictionary/Homeostasis>.Pack, Philips. Biology 2nd Edition. New York: Wiley, Print."Tissue (biology)." Wikipedia. Wikimedia Foundation, 03 July Web. 07 Mar<http://en.wikipedia.org/wiki/Tissue_(biology)>."Thermoregulation." Wikipedia. Wikimedia Foundation, 03 June Web. 07 Mar<http://en.wikipedia.org/wiki/Thermoregulation>.