Unit 6.8. Motor Mechanisms and Behavior CAMPBELL BIOLOGY IN FOCUS. Urry Cain Wasserman Minorsky Jackson Reece

Transcription

1 CAMPBELL BIOLOGY IN FOCUS Urry Cain Wasserman Minorsky Jackson Reece Unit 6.8 Motor Mechanisms and Behavior Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge

2 Overview: The How and Why of Animal Activity Fiddler crabs feed with their small claw and wave their large claw Why do male fiddler crabs engage in claw-waving behavior? Claw waving is used to repel other males and to attract females

3 Figure 39.1

4 A behavior is an action carried out by muscles under control of the nervous system Behavior is subject to natural selection

5 Concept 39.1: The physical interaction of protein filaments is required for muscle function Muscle activity is a response to input from the nervous system Muscle contraction is an active process; muscle relaxation is passive

6 Muscle cell contraction relies on the interaction between protein structures Thin filaments consist of two strands of actin coiled around one another Thick filaments are staggered arrays of myosin molecules

7 Vertebrate Skeletal Muscle Vertebrate skeletal muscle moves bones and the body and is characterized by a hierarchy of smaller and smaller units A skeletal muscle consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle Each muscle fiber is itself a bundle of smaller myofibrils, which contain thick and thin filaments

8 Skeletal muscle is also called striated muscle because the regular arrangement of myofibrils creates a pattern of light and dark bands The functional unit of a muscle is called a sarcomere and is bordered by Z lines

9 Figure 39.2 Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Z lines Myofibril Sarcomere TEM Thick filaments (myosin) Thin filaments (actin) Z line M line Sarcomere 0.5 μm Z line

10 Figure 39.2a Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Z lines Myofibril Sarcomer e

11 Figure 39.2b Sarcomer e TEM Thick filaments (myosin) Thin filaments (actin) Z line M line Sarcomere 0.5 μm Z line

12 The Sliding-Filament Mechanism of Muscle Contraction According to the sliding-filament model, filaments slide past each other longitudinally, causing an overlap between thin and thick filaments

13 Figure 39.3 Relaxed muscle Z Sarcomere M Z Z M Z Contracting muscle 0.5 μm Fully contracted muscle Contracted sarcomere

14 The sliding of filaments relies on interaction between actin and myosin The head of a myosin molecule binds to an actin filament, forming a cross-bridge and pulling the thin filament toward the center of the sarcomere Muscle contraction requires repeated cycles of binding and release

15 Glycolysis and aerobic respiration generate the ATP needed to sustain muscle contraction

16 Figure Thin filaments Thick filament Thin filament Myosin head (low energy configuration) ATP 5 ATP 2 Thick filament Thin filament moves toward center of sarcomere. Actin ADP Myosin head (low energy configuration) ADP P Pi ADP i 4 Myosinbinding sites Pi Cross-bridge Myosin head (high energy configuration) 3

17 Figure 39.4a Thin filament 1 ATP ATP Myosin head (low energy configuration) Thick filament

18 Figure 39.4b 2 Acti n AD P Pi Myosinbinding sites Myosin head (high energy configuration)

19 Figure 39.4c 3 AD Pi P Crossbridge

20 Figure 39.4d 4 Thin filament moves toward center of sarcomere. Myosin head (low energy configuration)

21 The Role of Calcium and Regulatory Proteins The regulatory protein tropomyosin and the troponin complex, a set of additional proteins, bind to actin strands on thin filaments when a muscle fiber is at rest This prevents actin and myosin from interacting

22 Figure 39.5 Ca2+-binding sites Tropomyosi n Actin Troponin complex (a) Myosin-binding sites blocked Ca2+ Myosinbinding site (b) Myosin-binding sites exposed

23 For a muscle fiber to contract, myosin-binding sites must be uncovered This occurs when calcium ions (Ca2+) bind to the troponin complex and expose the myosin-binding sites Contraction occurs when the concentration of Ca2+ is high; muscle fiber contraction stops when the concentration of Ca2+ is low

24 The stimulus leading to contraction of a muscle fiber is an action potential in a motor neuron that makes a synapse with the muscle fiber The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine Acetylcholine depolarizes the muscle, causing it to produce an action potential

25 Figure 39.6 Axon of motor neuron Synaptic terminal T tubule Sarcoplasmic reticulum (SR) Mitochondrio n Myofibril Plasma membrane of muscle fiber Ca2+ released from SR Sarcomere 1 Synaptic terminal of motor neuron Plasma Synaptic cleft T tubule membrane Sarcoplasmic reticulum (SR) 2 ACh Ca2+ pump 3 Ca2+ ATP 4 CYTOSOL 7 6 Ca2+ 5

26 Action potentials travel to the interior of the muscle fiber along transverse (T) tubules, infoldings of the plasma membrane The action potential along T tubules causes the sarcoplasmic reticulum (SR), a specialized endoplasmic reticulum, to release Ca2+ The Ca2+ binds to the troponin complex on the thin filaments, initiating muscle fiber contraction

27 When motor neuron input stops, the muscle cell relaxes Transport proteins in the SR pump Ca2+ out of the cytosol Regulatory proteins bound to thin filaments shift back to the myosin-binding sites

28 Amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig s disease) interferes with the excitation of skeletal muscle fibers; this disease is usually fatal Myasthenia gravis is an autoimmune disease that attacks acetylcholine receptors on muscle fibers; treatments exist for this disease

29 Nervous Control of Muscle Tension Contraction of a whole muscle is graded, which means that the extent and strength of its contraction can be voluntarily altered There are two basic mechanisms by which the nervous system produces graded contractions Varying the number of fibers that contract Varying the rate at which fibers are stimulated

30 In vertebrates, each motor neuron may synapse with multiple muscle fibers, although each fiber is controlled by only one motor neuron A motor unit consists of a single motor neuron and all the muscle fibers it controls

31 Figure 39.7 Spinal cord Motor unit 1 Motor unit 2 Synaptic terminals Nerve Motor neuron cell body Motor neuron axon Muscle Muscle fibers Tendon

32 Recruitment of multiple motor neurons results in stronger contractions A twitch results from a single action potential in a motor neuron More rapidly delivered action potentials produce a graded contraction by summation

33 Figure 39.8 Tension Tetanus Summation of two twitches Single twitch Action potential Time Pair of action potentials Series of action potentials at high frequency

34 Tetanus is a state of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials

35 Types of Skeletal Muscle Fibers There are several distinct types of skeletal muscles, each of which is adapted to a particular set of functions They are classified by the source of ATP powering the muscle activity and the speed of muscle contraction

36 Table 39.1

37 Oxidative and glycolytic fibers are differentiated by their energy source Oxidative fibers rely mostly on aerobic respiration to generate ATP These fibers have many mitochondria, a rich blood supply, and a large amount of myoglobin Myoglobin is a protein that binds oxygen more tightly than hemoglobin does

38 Glycolytic fibers use glycolysis as their primary source of ATP Glycolytic fibers have less myoglobin than oxidative fibers and tire more easily In poultry and fish, light meat is composed of glycolytic fibers, while dark meat is composed of oxidative fibers

39 Fast-twitch and slow-twitch fibers are differentiated by their speed of contraction Slow-twitch fibers contract more slowly but sustain longer contractions All slow-twitch fibers are oxidative Fast-twitch fibers contract more rapidly but sustain shorter contractions Fast-twitch fibers can be either glycolytic or oxidative

40 Most human skeletal muscles contain both slowtwitch and fast-twitch muscles in varying ratios Some vertebrates have muscles that twitch at rates much faster than human muscles In producing its characteristic mating call, the male toadfish can contract and relax certain muscles more than 200 times per second

41 Figure 39.9

42 Other Types of Muscle In addition to skeletal muscle, vertebrates have cardiac muscle and smooth muscle Cardiac muscle, found only in the heart, consists of striated cells electrically connected by intercalated disks Cardiac muscle can generate action potentials without neural input

43 In smooth muscle, found mainly in walls of hollow organs such as those of the digestive tract, contractions are relatively slow and may be initiated by the muscles themselves Contractions may also be caused by stimulation from neurons in the autonomic nervous system

44 Concept 39.2: Skeletal systems transform muscle contraction into locomotion Skeletal muscles are attached in antagonistic pairs, the actions of which are coordinated by the nervous system The skeleton provides a rigid structure to which muscles attach Skeletons function in support, protection, and movement

45 Figure Human forearm (internal skeleton) Extensor muscle Flexion Biceps Grasshopper tibia (external skeleton) Flexor muscle Tricep s Extension Biceps Extensor muscle Flexor muscle Tricep s Key Contracting muscle Relaxing muscle

46 Types of Skeletal Systems The three main types of skeletons are Hydrostatic skeletons (lack hard parts) Exoskeletons (external hard parts) Endoskeletons (internal hard parts)

47 Hydrostatic Skeletons A hydrostatic skeleton consists of fluid held under pressure in a closed body compartment This is the main type of skeleton in most cnidarians, flatworms, nematodes, and annelids Annelids use their hydrostatic skeleton for peristalsis, a type of movement on land produced by rhythmic waves of muscle contractions

48 Figure Longitudinal muscle relaxed (extended) Circular muscle Circular contracted muscle relaxed Bristles Longitudinal muscle contracted Head end 1 Head end 2 3 Head end

49 Exoskeletons An exoskeleton is a hard encasement deposited on the surface of an animal Exoskeletons are found in most molluscs and arthropods Arthropods have a jointed exoskeleton called a cuticle, which can be both strong and flexible About 30 50% of the arthropod cuticle consists of a polysaccharide called chitin An arthropod must shed and regrow its exoskeleton when it grows

50 Endoskeletons An endoskeleton consists of a hard internal skeleton, buried in soft tissue Endoskeletons are found in organisms ranging from sponges to mammals A mammalian skeleton has more than 200 bones Some bones are fused; others are connected at joints by ligaments that allow freedom of movement

51 Figure Shoulder girdle Sternu m Rib Humerus Vertebr a Radius Ulna Pelvic girdle Clavicle Scapul a Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsal s Phalanges Skul l Types of joints Ball-and-socket joint Hinge joint Pivot joint

52 Figure Ball-and-socket joint Head of humerus Scapula Hinge joint Humerus Ulna Pivot joint Ulna Radius

53 Size and Scale of Skeletons An animal s body structure must support its size The weight of a body increases with the cube of its dimensions, while the strength of that body increases with the square of its dimensions

54 The skeletons of small and large animals have different proportions In mammals and birds, the position of legs relative to the body is very important in determining how much weight the legs can bear

55 Types of Locomotion Most animals are capable of locomotion, or active travel from place to place In locomotion, energy is expended to overcome friction and gravity

56 Flying Active flight requires that wings develop enough lift to overcome the downward force of gravity Many flying animals have adaptations that reduce body mass For example, birds have no teeth or urinary bladder, and their relatively large bones have air-filled regions

57 Locomotion on Land Walking, running, or hopping on land requires an animal to support itself and move against gravity Diverse adaptations for locomotion on land have evolved in vertebrates For example, kangaroos have large, powerful muscles in their hind legs, suitable for hopping

58 Figure 39.14

59 Swimming In water, friction is a bigger problem than gravity Fast swimmers usually have a sleek, torpedo-like shape to minimize friction Animals swim in diverse ways Paddling with their legs as oars Jet propulsion Undulating their body and tail from side to side or up and down

60 Concept 39.3: Discrete sensory inputs can stimulate both simple and complex behaviors Niko Tinbergen identified four questions that should be asked about animal behavior 1. What stimulus elicits the behavior, and what physiological mechanisms mediate the response? 2. How does the animal s experience during growth and development influence the response?

61 3. How does the behavior aid survival and reproduction? 4. What is the behavior s evolutionary history? Behavioral ecology is the study of the ecological and evolutionary basis for animal behavior

62 Behavioral ecology integrates proximate and ultimate explanations for animal behavior Proximate causation addresses how a behavior occurs or is modified, including Tinbergen s questions 1 and 2 Ultimate causation addresses why a behavior occurs in the context of natural selection, including Tinbergen s questions 3 and 4

63 Fixed Action Patterns A fixed action pattern is a sequence of unlearned, innate behaviors that is unchangeable Once initiated, it is usually carried to completion A fixed action pattern is triggered by an external cue known as a sign stimulus

64 Tinbergen observed male stickleback fish responding to a passing red truck In male stickleback fish, the stimulus for attack behavior is the red underside of an intruder When presented with unrealistic models, the attack behavior occurs as long as some red is present

65 Figure (a) (b)

66 Migration Environmental cues can trigger movement in a particular direction Migration is a regular, long-distance change in location Animals can orient themselves using The position of the sun and their circadian clock, an internal 24-hour activity rhythm or cycle The position of the sun or stars Earth s magnetic field

67 Behavioral Rhythms Some animal behavior is affected by the animal s circadian rhythm, a daily cycle of rest and activity Behaviors such as migration and reproduction are linked to changing seasons, or a circannual rhythm Daylight and darkness are common seasonal cues Some behaviors are linked to lunar cycles, which affect tidal movements

68 Animal Signals and Communication In behavioral ecology, a signal is a behavior that causes a change in another animal s behavior Communication is the transmission and reception of signals

69 Forms of Animal Communication Animals communicate using visual, chemical, tactile, and auditory signals Fruit fly courtship follows a three-step stimulusresponse chain

70 1. A male identifies a female of the same species and orients toward her Chemical communication: he smells a female s chemicals in the air Visual communication: he sees the female and orients his body toward hers

71 2. The male alerts the female to his presence Tactile communication: he taps the female with a foreleg

72 3. The male produces a courtship song to inform the female of his species Auditory communication: he extends and vibrates his wing If all three steps are successful, the female will allow the male to copulate

73 Honeybees show complex communication with symbolic language A bee returning from the field performs a dance to communicate information about the distance and direction of a food source

74 Figure (b) Round dance (food near) (a) Worker bees (c) Waggle dance (food distant) 30 A 30 C B Beehive Location A Location B Location C

75 Pheromones Many animals that communicate through odors emit chemical substances called pheromones

76 For example, A female moth can attract a male moth several kilometers distant A honeybee queen produces a pheromone that affects the development and behavior of female workers and male drones When a minnow or catfish is injured, an alarm substance in the fish s skin disperses in the water, causing nearby fish to seek safety

77 Animals use diverse forms of communication Nocturnal animals, such as most terrestrial mammals, depend on olfactory and auditory communication Diurnal animals, such as humans and most birds, use visual and auditory communication

78 Concept 39.4: Learning establishes specific links between experience and behavior Innate behavior is developmentally fixed and does not vary among individuals

79 Experience and Behavior Cross-fostering studies help behavioral ecologists to identify the contribution of environment to an animal s behavior A cross-fostering study places the young from one species in the care of adults from another species

80 Studies of California mice and white-footed mice have uncovered an influence of social environment on aggressive and parental behaviors Cross-fostered mice developed some behaviors that were consistent with their foster parents

81 Table 39.2

82 In humans, twin studies allow researchers to compare the relative influences of genetics and environment on behavior

83 Learning Learning is the modification of behavior based on specific experiences

84 Imprinting Imprinting is the establishment of a long-lasting behavioral response to a particular individual Imprinting can only take place during a specific time in development, called the sensitive period A sensitive period is a limited developmental phase that is the only time when certain behaviors can be learned

85 An example of imprinting is young geese following their mother Konrad Lorenz showed that when baby geese spent the first few hours of their life with him, they imprinted on him as their parent The imprint stimulus in greylag geese is a nearby object that is moving away from the young geese

86 Figure (a) Konrad Lorenz and geese (b) Pilot and cranes

87 Conservation biologists have taken advantage of imprinting in programs to save the whooping crane from extinction Young whooping cranes can imprint on humans in crane suits who then lead crane migrations using ultralight aircraft

88 Spatial Learning and Cognitive Maps Spatial learning is the establishment of a memory that reflects the spatial structure of the environment Niko Tinbergen showed how digger wasps use landmarks to find nest entrances

89 Figure Experiment Nest Pinecone Results Nest No nest

90 A cognitive map is an internal representation of spatial relationships between objects in an animal s surroundings For example, Clark s nutcrackers can find food hidden in caches located halfway between particular landmarks

91 Associative Learning In associative learning, animals associate one feature of their environment with another For example, a blue jay will avoid eating butterflies with specific colors after a bad experience with a distasteful monarch butterfly

92 Figure 39.19

93 Animals can learn to link many pairs of features of their environment, but not all For example, pigeons can learn to associate danger with a sound but not with a color For example, rats can learn to avoid illness-inducing foods on the basis of smells, but not on the basis of sights or sounds

94 Cognition and Problem Solving Cognition is a process of knowing that may include awareness, reasoning, recollection, and judgment For example, honeybees can distinguish same from different

95 Problem solving is the process of devising a strategy to overcome an obstacle For example, chimpanzees can stack boxes in order to reach suspended food For example, ravens obtained food suspended from a branch by a string by pulling up the string

96 Social learning is learning through the observation of others and forms the roots of culture For example, young chimpanzees learn to crack palm nuts with stones by copying older chimpanzees

97 Culture is a system of information transfer through observation or teaching that influences behavior of individuals in a population Culture can alter behavior and influence the fitness of individuals

98 Concept 39.5: Selection for individual survival and reproductive success can explain most behaviors Behavior enhances survival and reproductive success in a population Foraging is a behavior essential for survival and reproduction that includes recognizing, capturing, and eating food items

99 Evolution of Foraging Behavior Natural selection refines behaviors that enhance the efficiency of feeding

100 In Drosophila melanogaster, variation in a gene dictates foraging behavior in the larvae Larvae with one allele travel farther while foraging than larvae with the other allele Larvae in high-density populations benefit from foraging farther for food, while larvae in low-density populations benefit from short-distance foraging

101 Natural selection favors different alleles depending on the density of the population Under laboratory conditions, evolutionary changes in the frequency of these two alleles were observed over several generations

102 Figure Mean path length (cm) 7 Low population density 6 High population density R1 R2 R3 K1 D. melanogaster lineages K2 K3

103 Mating Behavior and Mate Choice Mating behavior includes seeking or attracting mates, choosing among potential mates, competing for mates, and caring for offspring Mating relationships define a number of distinct mating systems

104 Mating Systems and Sexual Dimorphism The mating relationship between males and females varies greatly from species to species In some species there are no strong pair-bonds In monogamous relationships, one male mates with one female Males and females with monogamous mating systems have similar external morphologies

105 Figure (a) Monogamous species (b) Polygynous species (c) Polyandrous species

106 In polygamous relationships, an individual of one sex mates with several individuals of the other sex Species with polygamous mating systems are usually sexually dimorphic: males and females have different external morphologies Polygamous relationships can be either polygynous or polyandrous

107 In polygyny, one male mates with many females The males are usually more showy and larger than the females

108 In polyandry, one female mates with many males The females are often more showy than the males

109 Mating Systems and Parental Care Needs of the young are an important factor constraining evolution of mating systems

110 Consider bird species where chicks need a continuous supply of food A male maximizes his reproductive success by staying with his mate and caring for his chicks (monogamy) Consider bird species where chicks are soon able to feed and care for themselves A male maximizes his reproductive success by seeking additional mates (polygyny)

111 Certainty of paternity influences parental care and mating behavior Females can be certain that eggs laid or young born contain her genes; however, paternal certainty depends on mating behavior Paternal certainty is relatively low in species with internal fertilization because mating and birth are separated over time

112 Certainty of paternity is much higher when egg laying and mating occur together, as in external fertilization In species with external fertilization, parental care is at least as likely to be by males as by females

113 Figure 39.22

114 Sexual Selection and Mate Choice Sexual dimorphism results from sexual selection, a form of natural selection In intersexual selection, members of one sex choose mates on the basis of certain traits Intrasexual selection involves competition between members of the same sex for mates

115 Female choice is a type of intersexual competition Females can drive sexual selection by choosing males with specific behaviors or features of anatomy For example, female stalk-eyed flies choose males with relatively long eyestalks Ornaments, such as long eyestalks, often correlate with health and vitality

116 Figure 39.23

117 Male competition for mates is a source of intrasexual selection that can reduce variation among males Such competition may involve agonistic behavior, an often ritualized contest that determines which competitor gains access to a resource

118 Concept 39.6: Inclusive fitness can account for the evolution of behavior, including altruism The definition of fitness can be expanded beyond individual survival to help explain selfless behavior

119 Genetic Basis of Behavior Differences at a single locus can sometimes have a large effect on behavior For example, male prairie voles pair-bond with their mates, while male meadow voles do not The level of a specific receptor for a neurotransmitter determines which behavioral pattern develops

120 Figure 39.24

121 Genetic Variation and the Evolution of Behavior When behavioral variation within a species corresponds to environmental variation, it may be evidence of past evolution

122 Case Study: Variation in Prey Selection The natural diet of western garter snakes varies by population Coastal populations feed mostly on banana slugs, while inland populations rarely eat banana slugs Studies have shown that the differences in diet are genetic The two populations differ in their ability to detect and respond to specific odor molecules produced by the banana slugs

123 Figure 39.25

124 Altruism Natural selection favors behavior that maximizes an individual s survival and reproduction These behaviors are often selfish On occasion, some animals behave in ways that reduce their individual fitness but increase the fitness of others This kind of behavior is called altruism, or selflessness

125 For example, under threat from a predator, an individual Belding s ground squirrel will make an alarm call to warn others, even though calling increases the chances that the caller is killed For example, in naked mole rat populations, nonreproductive individuals may sacrifice their lives protecting their reproductive queen and kings from predators

126 Figure 39.26

127 Inclusive Fitness Altruism can be explained by inclusive fitness Inclusive fitness is the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring

128 Hamilton s Rule and Kin Selection William Hamilton proposed a quantitative measure for predicting when natural selection would favor altruistic acts among related individuals Three key variables in an altruistic act Benefit to the recipient (B) Cost to the altruistic (C) Coefficient of relatedness (the fraction of genes that, on average, are shared; r)

129 Natural selection favors altruism when rb C This inequality is called Hamilton s rule Hamilton s rule is illustrated with the following example of a girl who risks her life to save her brother

130 Assume the average individual has two children. As a result of the sister s action The brother can now father two children, so B = 2 The sister has a 25% chance of dying and not being able to have two children, so C = = 0.5 The brother and sister share half their genes on average, so r = 0.5 If the sister saves her brother, rb (= 1) C (= 0.5)

131 Figure Parent A Parent B OR ½ (0.5) probability ½ (0.5) probability Sibling 1 Sibling 2

132 Kin selection is the natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives