BSC 116 BSC 116
Popular in Principles Biology II
verified elite notetaker
Popular in Biological Sciences
verified elite notetaker
This 12 page Class Notes was uploaded by Ashley Bartolomeo on Sunday April 17, 2016. The Class Notes belongs to BSC 116 at University of Alabama - Tuscaloosa taught by Professor Harris in Spring 2016. Since its upload, it has received 14 views. For similar materials see Principles Biology II in Biological Sciences at University of Alabama - Tuscaloosa.
Reviews for BSC 116
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/17/16
Sensor & Motor Mechanisms – Part I Overview Different types of receptors code external stimuli as action potentials o E.g., chemoreceptors, mechanoreceptors, photoreceptors Coded input leads to coded response (more action potential) Animals Take in Information, Process it & Respond Sensory input gets integrated into the central nervous system (brain, nerve cord), response is transmitted by the peripheral nervous system Neurons: specialized cells that conduct and store information in the nervous system Sensory Receptors Convert Stimulus Energy into Changes in Membrane Potential There are 4 stages to getting a stimulus to the brain: 1. Reception: sensory call detects stimulus a. E.g. stretching of mechanoreceptor opens ion changes 2. Transduction: conversion of stimulus to receptor potential a. Graded: magnitude varies with intensity of stimulus 3. Transmission: if receptor potential initiates action potential a. Receptor cell: axon or neurotransmitter b. Strength of stimulus modulates frequency of action potential c. Integration = processing might begin even before transmission i. Summation on a single receptor cell, multiple receptor cells acting on a single afferent neuron, etc. 4. Perception: CNS (brain) processing of input from sensory neurons i. All perceptions are coded by the paths their action potentials travel Transduction can be modified in two ways o Amplification: strengthening the stimulus; adding energy E.g., signal transduction pathways, anatomical modifications o Adaptation (not to be confused with adaptation): become unresponsive to constant stimulation E.g., keep you from being overwhelmed by sensation Different Types of Sensory Receptors Respond to Different Stimuli Chemoreceptors: bind molecules, initiates change in membrane potential o Non specific to measure solute concentration o Specific for different molecules o E.g., taste, smell Mechanoreceptors: deformed or moved to sense pressure, stretch, motion, etc. o Often ion channels linked to cilia o Or dendrites in association with muscles, hair, etc. o E.g., touch receptors in skin, hearing Electromagnetic receptors: detect light, electricity, magnetism, etc. o E.g., eyes to detect light o E.g., vipers have pits to detect body heat (infrared) o E.g., certain fish detect electrical currents o E.g., magnetite in many different organisms detect magnetic fields Thermoreceptors: detect hot and cold o Membrane proteins change shape under different temperatures o Can be tricked by binding certain chemicals: capsaicin (from peppers) or menthol Nociceptors: detect “pain”, like extreme pressure, chemicals, etc. o Highest density in skin Taste and Small Both Rely on Chemoreceptors Chemoreceptors for various aspects of an animal’s life: e.g., find mates, recognize territory, navigation, communication, etc. Gustation = taste; detection of tastants in solution o In mammals, receptors concentrated on taste-buds on tongue Recognize sweet, sour, salty, bitter & savory(glutamate) Different mechanisms: G-protein transduction or TRP Many different kinds of cells, each with single receptor o In insects, on bottom of feet and mouth parts Olfaction = smell; detection of odorants in air o In mammals, receptors in upper nasal cavity Binding specific odorants leads to G-protein transduction >1000 human genes dedicated to olfactory receptor proteins Different types of chemoreception connect to different parts of the brain Hearing and Balance are both Based Upon Mechanoreceptors In many animals the organs for hearing & equilibrium are closely associated o E.g., in humans: ears Gist of hearing: pressure waves in the air deform receptor cells, leads to membrane potential Starts with conversion of waves in air to fluid o Outer ear: tympanic membrane (“eardrum”) vibrates o Middle ear: three tiny bones transmit vibration o Inner ear: cochlea receives vibration Waves flow down vestibular canal, cause vibrations that stimulate hair cells o Hair cells releasing neurotransmitter all the time o Vibrations in one direction depolarize, other direction hyperpolarize Sound stimulus has both volume and pitch o Volume: the magnitude of the vibrations o Pitch = frequency: basilar of varying thickness; different parts vibrate in response to different pitches Hearing is just the Perception of Vibrations Fish live in water: no need to convert air pressure waves to fluid pressure waves o No outer ears: vibrations pass from water, thru body Vibrate ear bones, as well as swim bladder o Lateral line system: mechanoreceptors for detecting low- frequency vibrations Hair cells as in mammal inner ear Insects: have “hairs” on their bodies that vibrate o Tuned to specific frequencies to hear specific sounds E.g., predators, mates o Some insects have a tympanic membrane (like an eardrum) Specific organ to detect vibrations E.g., cockroach Balance Requires Sensing Orientation Relative to Gravity & Angular Momentum Many mammals have statocyts to sense gravity o Chamber surrounded by ciliated cells o Statoliths move around as body moves In mammals, balance associated with ears o Inner ear has utricle (horizontal) and saccule (vertical) o Chambers lined with hair cells and little stones (otoliths) o Tilting your head, causes the stones to move Our semicircular canals detect angular momentum o Oriented in three planes Most Animals Have Some Way to Detect Light Photoreceptors: cells that detect light o Various morphological arrangements to detect light direction, intensity, wavelength, etc. Ocelli: simple cup of photoreceptors o E.g., planaria o Cup creates shadow to determine light direction Single lens eyes: functions kind of like a camera o E.g., jellies, some annelids, spiders, some mollusks, vertebrates o Single opening with a lens to focus light on a field of photoreceptors Compound eyes: composed of many light detectors o E.g., insects o Each facet has own lens, responsible for a small part of the visual field The Vertebrate Eye is the Single Lens Type “Eye ball” has three layers o Outer sclera: white, connective tissue o Middle choroid: colored o Inner retina: layers of neurons & photoreceptor Light enters at one end o Cornea: transparent area of sclera o Surround by iris (choroid); moves to adjust to regulate light Pupil: the actual hole for light o Lens: transparent protein Focuses light by changing shape Entering light focused on the retina o Retina has two types of photoreceptors Rods: sensitive to light but not colors Cones: distinguish colors, but not very light sensitive o Proportion/ number of each varies with lifestyle o Fovea center of focus: 150,000 cones/ mm^2 Rods & Cones Change Light Energy into Chemical Energy, which is Transmitted to the Brain Rhodopsin: visual pigment in rods o In membrane of stacked disks in each rod o Absorption of light changes its shape: inactive to active Active rhodopsin leads to signal transduction that closes Na+ channels o In dark, rods depolarized, releasing neurotransmitters o Light causes hyperpolarization, no neurotransmitters o Works similarly with the photopsins of cones Photoreceptors interact with a variety of different neuron types o Process the information from each receptor o Ganglion cell axons transmit impulses to brain o Visual centers are located in the posterior part of the brain Each half of visual field supported by opposite side of the brain Overview Effector neurons work on muscles o Action is contraction of muscle fibers Sliding filament model of muscle function Contraction is the sum of many twitches Turning muscle contraction into action Animals Respond to Stimuli with Action Using Muscles All this stimulation (sensory input) is processed in the CNS o Mostly in the brain Complicated integration of signals leads to a response o Information based on which neurons are firing Response can act on the endocrine system Response can act on muscles Skeletal Muscle Contracts to Move Skeletal Elements Vertebrate skeletal muscle attached to bones: responsible for movement, locomotion, etc. Characteristic organization: linear fibers within fibers o Muscle: bundle of fibers running parallel to bone o Fiber: single cell (multiple nuclei) with bundle of myofibrils o Myofibrils composed of thin (actin) & thick (myosin) filaments Sarcomere: basic contractile unit of myofibril o Ends of actin fibers line up at ends: z lines o Middle of myosin fibers lined up: m line o “Striated muscles”: array of adjacent sarcomeres Muscles contract by actin and myosin sliding past each other: sliding- filament model Filaments do not change length when sarcomere shortens, filaments just slide over each other, increasing overlap The Sliding Filament Model Myosin molecule: long tail and round head o Tails of myosin stick together in thick fiber o Head is where all the action is 1. Head binds ATP (low-energy configuration) 2. Head hydrolyzes ATP to ADP, uses energy to change shape: head moves forward 3. Head binds to adjacent thin (actin) filament 4. Head releases ADP but holds on to actin o Changes shape to pull thick filament against thin 5. Binding new ATP causes head to release Cycle starts over… Ca2+ & Regulatory Proteins Control Contraction of Muscle Fibers Two sets of regulatory proteins are bound to the thin (actin) filaments o Tropomyosin: coils around actin o Troponin Complex: arranged along tropomyosin o Proteins block myosin binding sites: inhibits actin-myosin interaction; no sliding Ca2+ in cytoplasm binds troponin complex: results in exposure of binding sites; sliding can occur An Action Potential Leads to Myofibril Contraction 1. With action potential, motor neuron releases acetylcholine (neurotransmitters), binds to receptors on muscles 2. Triggers action potential, transverse tubules (extensions of plasma membrane) carry AP deep into muscle cell 3. AP causes sarcoplasmic reticulum to release Ca2+ 4. Troponin complex & tropomyosin move out of the way 5. Sarcomere contracts 6. When motor neuron stops firing, Ca2+ pumped back to SR 7. Troponin complex & tropomyosin move back in the way, fiber relaxes Like action potential, muscle fiber contraction is “all or nothing”: a twitch Whole Muscle Contraction is the Sum of Many Twitches Whereas fibers are “all or nothing”. Muscle contraction is graded Each fiber controlled by one motor neuron Each motor neuron controls many fibers o Motor unit: all fibers controlled by one neuron All contract together o One muscle may be controlled by hundreds of neurons Strength of contraction depends on number of neurons recruited and the size of the motor units they control Rapid AP’s lead to rapid twitches: can sum o Tension may not be lost between them: tetanus “Twitches” smoothed out by elastic tendons connecting to bones Some Sort of Skeleton is Necessary to Turn Contraction in Action Whether muscles surround bone skeleton (endoskeleton) or muscle within skeleton (exoskeleton), only contraction causes movement o Muscle work in antagonistic pairs Many animals like mineralized or chitin skeletons: rely on hydrostatic skeleton o Body cavity filled with non-compressible fluid o Contracting longitudinal muscles (parallel to body axis) causes body to shorten o Contracting circular muscles (around diameter of body) causes body to lengthen Skeletal is just one kind of Vertebrate Muscle Skeletal muscle is composed of multiple fiber types Cardiac muscle: found only in the heart o Striated like skeletal muscle o Can generate own action potentials without nervous input o “Pacemaker” generates rhythmic contractions o Cells connected by gap junctions: spreads AP Smooth muscle: in walls of hollow organs (blood vessels, gut, etc,.) o Not striated: no sarcomeres o Thin (actin) fibers attached to plasma membrane; thick (myosin) fibers scattered in cytoplasm o Contractions not parallel Animal Behavior Lecture 35 Overview All behavior is based upon both environment and genotype Learning is the influence of environment on behavior Innate behaviors are those with a strong genetic component Variation is genes means natural selection can act on behavior So can sexual selection The problem of altruistic behavior Animals Have Behavior Behavior: sum of all of an organism’s responses to stimuli o Nervous system determines how: Stimuli sensed Sensory input processed To respond Behavior is a trait: phenotype o Has genetic component (genotype) o Has an environmental component o Can be acted on by natural selection, if there is genetic variation Ethology: study of animal behavior in natural environments We want to explain behavior at two levels o Proximate causation: what stimulus leads to the response? Short term; how? o Ultimate causation: what is the evolutionary history of this trait? Long term; why? Sometimes Proximate Causes of Behavior Are Easy to Determine For many behaviors, a particular stimulus leads to a particular response Taxis: moving toward or away from a stimulus o E.g., fish generally orient upstream o E.g., moths fly toward a flame Fixed action patterns: some trigger leads to a behavior; must be carried to completion o E.g., male sticklebacks attack other males in their nests (Actually, simple presence of red leads to attack) o E.g., graylag goose & egg rolling behavior Communication: one animal’s signal leads to another’s response o Can be visual, chemical, chemical, tactile o E.g., female fiddler crab moves toward a male waving his claw o E.g., minnows hide in the presence of alarm pheromone The Environment of an Organism Can Influence its Behavior Innate behavior: traits that are fixed by genotype and development o E.g., minnows respond to pheromones Individuals with the same genotype can have different behavioral phenotypes o Learning: modifying behavior based upon experience Habituation: like sensory adaptation; stop responding to stimulus that requires no response o Allows distinguishing what is new & important stimuli from old & repetitious o Widespread among animals o E.g., prairie dogs that live near humans “get used to” presence Imprinting: many birds “learn” who their mother is during a brief period after birth o Necessary for bonding between parents and offspring; egg layers o E.g., graylag geese imprint on who/ whatever is there when they are born To Determine the Magnitude of Environmental Effects we need to Control for Genetics Behavior the result of complex interaction of environment & genotype o Not one or the other, “nature vs. nurture” How much of a behavior is innate? How much is learned? Raise the same/ similar genotypes in different environments: difference is environmental o Cross fostering studies: offspring of one species raised by another E.g., California mice & white footed mice California mice: aggressive, extensive parental care White footed mice: not aggressive, less parental care o Twin studies: look at identical twin’s places with different foster families Useful for demonstrating effects of environment on identical genotypes All Types of Animals Are Capable of Learned Behavior The range in complexity of learned behavior among animals is huge o The capacity to learn is innate: varies among taxa Associative learning: associated one stimulus with another o Classical conditioning: arbitrary stimulus leads to certain response E.g., Pavlov’s dogs, Planaria o Operant conditioning: trial and error learning E.g., rat learning a maze Spatial learning: maintaining an internal “map” o E.g., digger wasps use visible landmarks to find nest Know what the area looks like by their nest Cognition: reasoning, awareness o E.g., honeybees can be trained to recognize “same” and “different” Problem solving: requires being able to see solutions past obstacles o E.g., the raven and the string o Many animals can learn by observation E.g., octopuses and jar opening Genetic Variation in a Population Can Lead to Behavioral Variation There is also a genetic component to behavior E.g., blackcaps (warbler) o Breed in Germany, migrate winter in Spain/ Africa o 1950s, a few started breeding in UK Now thousands o Raised chicks in lab from parents captured in Germany and UK Offspring of birds captured in Germany: tended to migrate SW (to Spain) Offspring of birds captured in UK: tend to fly W (to UK) o Migration direction depends on parents (genotype), not where raised E.g., western garter snake o Populations near coast eat banana slugs, inland populations don’t (not naturally available, wont when offered) o Raised babies in lab collected from wild mothers from each population Both offered banana slug chunks on each of ten days Coastal snakes: >60 % ate slug chunks almost every day Inland snakes: <20 % ever ate slug chunk o Food preference depends on parent population (genotype), not where raised o (actual difference based upon presence of olfactory receptors for slugs) Because there is genetically based variation in these traits in these populations, natural selection can act on them The Ultimate Causes of Many Behavioral Traits Are Evolutionary Genes that lead to traits (including behavior) that lower chances of survival or reproduction are removed from populations Thus, we would expect natural selection to refine behaviors to maximize survival and reproduction; 4 examples o Optimal foraging o Mate choice and parental care o Sexual selection o Frequency dependent selection/ game theory Optimal Foraging Theory is Based Upon Trade-offs Foraging = looking for food o Benefit: nutrition, cot: time, energy, exposure Optimal foraging: maximize benefit, minimize cost E.g., fruit fly larval foraging: rovers and sitters o Rovers travel 2x more while feeding as sitters o Both traits occur in natural populations, favored under different conditions Less roving in low density populations E.g., cross eating snails o Open shell by dropping the snail from the air o Higher flight: benefit more force, cost more energy/ time spent o Are crows maximizing benefit and minimizing cost? Mating Systems Are Related to the Parental Roles Different species have different mating behaviors o Monogamous: long term pair bonding o Polygamous: multiple, long term pair bonding Polygyny: one male, multiple females Polyandry: one female, many males (uncommon) o Promiscuous: no pair bonding Rated to the needs of offspring o Baby birds needs lots of care, birds often monogamous (for season) o Mammal females often provide most nutrition (milk), polygamous or promiscuous Mating System is Related to the Parental Roles Parental care also related to certainty of paternity o Benefit of raising own offspring vs. cost of raising someone else’s o Females have a high certainty of maternity o Internal fertilization (time between mating and egg laying/ birth), males have low certainty of paternity Few species of birds & mammals raised by only males Leads to male behaviors that increase certainly of paternity: guarding females, sperm removal before copulation, produce lots of sperm, etc. E.g., bats that live in large groups have larger testicles: sperm competition o External fertilization (no time between fertilization & egg laying), males have high certainty of paternity Among invertebrates and fish, if there is parental care just as likely to be male IMPORTANT: males aren’t aware of certainty of paternity; selection has favored males with behaviors that increase likelihood that their energy is spent on their own offspring Sexual Selection Has Behavioral Effects Sexual selection: result of differential mating success when there is competition for mates o Leads to sexual dimorphism in traits that might not be favored by natural selection; appearance & behavior Males (usually) compete to attract females (choosy); e.g., peacock tails and bright colors, songs o Trait favored because it demonstrates overall health o Often leads to runaway selection (positive feedback) E.g., if females favor long eye stalks, then longer eye stalks are better o Results in lower variation among males o Females remain “drab” because there is a cost to showy ornamentation Males physically compete for females; e.g., bighorn sheep o Trait favored in agonistic interactions among males o Also reduces variation among males Sexual Selection Can Also Increase Variation Among Males E.g., side-blotched lizards have three different throat colors, with each different behavior o Orange: aggressive, defend large territories with many females o Blue: defend smaller territories with fewer females o Yellow: non territorial (“sneaky”) Which phenotype has advantage depends upon which is the most common o Blue (small territories): can keep out sneaky yellows, but lose in competition with aggressive orange o Orange (large territories): can beat less aggressive blues, but sneaky yellows can slip into large territories o Yellow (non territorial): can’t compete with blues Favored phenotype frequency dependent, changes over time o Game theory is a branch of mathematics that deals with this Altruism Presents a Problem for Evolutionary Theory Altruism: doing something that lowers your own fitness but increases someone else’s o E.g., Belding’s ground squirrel that gives an alarm call when it sees a predator: group gets a warning, caller attracts the predator Paradox: how can natural selection favor a trait that lowers fitness? o In a population of altruists, selection favors jerks E.g., parent-offspring relationship seems highly asymmetrical o Parent provides care, but what does the offspring provide? Parent is actually looking after their genes o Offspring caries 0.5 of each parents’ genes o By looking after the child’s fitness, the parent is also looking after part of its own fitness The Idea of Inclusive Fitness Solves the Problem Inclusive fitness: fitness (representation of your genes in the next generation) depends on your reproduction and that of your close relatives (William) Hamilton’s Rule: rB > C o Weigh the cost/benefit of an “Altruistic” act o C (cost) is the number of offspring that an action might cost the “altruist” o B (benefit) is the number of offspring that an action will gain the recipient o r (coefficient of relatedness): average number of genes shared by the two o as long as rB > C, then the benefit outweighs the cost Example of Hamilton’s Rule in Action consider a human (2 offspring on ave.) that risks their life to save their drowning sibling (an “altruistic” act) o Assume there is a 25% of drowning o B = kids sib has if they don’t drown = 2 o C = kids human has x chance of drowning = 2 x 0.25 = 0.5 o r = genes shared by sibs = 0.5 o Thus, on average saving the drowning sib would increase inclusive fitness, thus it is not an altruistic act A drowning cousin (r = 0.125, rB = 0.25) would not increase inclusive fitness and would be altruistic Now consider the ground squirrels again: live in groups of close relatives “Altruism” in nature is a selfish act to gives you own genes an advantage: kin selection Organisms aren’t aware of Hamilton’s Rule, but natural selection will favor these behaviors if they increase inclusive fitness
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'