Presentation on theme: "Exam 4 will cover new material through end of Animal Behavior Unit"— Presentation transcript:
1 Exam 4 will cover new material through end of Animal Behavior Unit (will complete lecture material for exam on Wednesday)
2 Adaptive function of stereotypical, “innate” behavior FAP’s, triggered by simple cues do not require extensive time otherwise required for neural processing or integrating wide variety of inputsSimple cue and relatively simple, stereotypical behavior patterns are effective evolutionary solutions to many situations in the lives of animals, including humans.Ultimate cause may be that for certain behaviors, automatic and experience-independent modes of expression may have maximized fitness to the point that genes for variant behavior were lost.Smiling appears spontaneously in human infants at about four weeks. The innate nature of this motor program is illustrated by the smile of this eleven week old blind girl, whose eyes are fixated on source of mother’s voice, a complex behavior that is also innate. Smiling helps cement a strong emotional attachment between parent and child
3 Approaches to investigating how genes affect behavior HybridizationArtificial selection and crossing of selected strainsMolecular analysis of genes and gene products
4 Hybridization experiment with two species lovebirds demonstrates 1) phenotypic differences in behavior are based on different genotypes, and 2) the behavior can be modified by experience
5 Artificial selection and cross of selected strains Genes and hygenic behavior in honeybeesUncommon instance in which behavioral trait segregates in Mendellian fashion; most behaviors are influenced by a wide array of genesSome honeybee strains express a hygenic behavior; they remove the carcasses of dead larvae from their nestsAdaptive function of behavior;confers resistance to bacterium lethal to larvaeTwo apparent components to this behavioruncapping larval cell (u)removing carcass (r)Cross-breeding experiments with hygenic and non-hygenic strains revealsimple Mendellian segregation of the genes coding for each behavioral componentall F1 progeny are non-hygenic; indicates each behavioral component is controlled by a recessive alleleback-crossing F1 with hygenic strain produces 3:1 phenotype ratio expected for a two-gene trait
6 Molecular genetics research reveals specific genes that influence behavior In Drosophila, male courtship behavior is stereotypic, species-specific, and requires no learningSexual differentiation is controlled by a hierarchy of genes, and in that hierarchy, fru controls the branch that leads to male courthship behaviorMost elements of male courtship behavior are controlled by a single gene
7 The fruitless gene controls male courtship in behavior in fruitflies sex-determining pre-mRNAs are spliced in a specific way in females and another way in malesMale sxl and tra mRNAs have stop codons that terminate translationfemale sxl and tra mRNAs make proteins that control splicing in the expression of genes in the female-specific hierarchythe default splicing of dsx mRNAs controls male anatomysexlethal (sxl) is expressed in females (two x chromosomes) (males are XY). sxl is at top of genetic hierarchy that determines all aspects of sexual differentiation and behaviorsxl protein causes the gene transformer (tra) to produce female-specific Tra proteinthe default splicing of fru mRNAs causes formation of nervous system that expresses male courtship behaviorsex-lethal (sxl) is at the top of a gene hierarchy; it is expressed in fly embryos with two x chromosomes (flies therefore destined to be females).
8 Learning: modification of behavior due to experience Learning in the context of genetic and environmental components of behaviorMany behaviors have a strong environmental component, and some behaviors may seem to be entirely due to learning, but at some level, all behaviors have a genetic componentLearning vs. maturation in developmentally fixed behaviorsMost developmentally fixed behaviors improve with performance as the animal learns to execute the behavior more efficientlyModification of a developmentally fixed behavior may be due to maturation (ongoing developmental changes in neuromuscular systems) in addition to or in the absence of learningJapanese macaque that has learned to wash sand off of food before eatingExample: the capacity to learn a language in humans seems entirely learned (ie german, spanish…), but the ability to learn to speak language in gereal is a function of a complex brain that develops in a particular environmental context under the guidance of a human genome
9 HabituationHabituation is a simple form of learning in which responsiveness to a stimulus is lostanimal learns to ignore a repeated, irrelevant stimulus, which is adaptive…fitness is probably increased through habituation, by allowing animal’s nervous system to focus on important stimuli that signal food, mates, or danger, instead of wasting time or energy on barrage of stimuli that are irrelevant to its survival and reproductionSolomon & Berg 1999After repeated safe encounters with vans transporting humans on photo safari, many animals, including giraffes, zebras, lions, and elephants, in the Serengeti learn to ignore them. Elephants typically ignore the vans unless the driver provokes them by moving too close. In that event the elephant may challenge and even charge the van
10 Imprinting in birds: mechanism and adaptive function Imprinting is learning that is limited to a specific time in an animal’s life, the critical period, and is generally irreversibleImprinting is a process by which social attachments are made early in life that will influence behavior later in lifeFilial imprinting; social attachments form between parents and offspringSexual imprinting; attachment forms by which an individual learns to direct it sexual behavior at members of its own speciesImprinted goslings following MomFilial imprinting; for example, young birds begin to follow their mother within a few hours after hatching and their following response results in a bond betrween motehr and young. however the youg bigds initial experienc3ee determines how this imprint is establishedImprinting in birds: mechanism and adaptive functionIn many bird species, young develop a strong behavioral bond with motherBond forms through imprinting, during a critical period -- usually within a few hours of hatchingBond forms through vocal communication; older embryos in eggs can exchange calls with nest-mates and parents through eggshell; one or both parents usually present at hatching and emitting calls
11 Lorenz investigated the phenomenon of imprinting Raven & Johnson 1999Lorenz investigated the phenomenon of imprintingNewly hatched bird imprints on the first moving object it sees (imprinting stimulus) and then will direct their social behavior toward that objectLorenz split a clutch of graylag goose eggs; left half with mother to incubate and raise; they showed normal behavior, followed her, grew up to interact and mate with conspecificsHalf the clutch placed incubator, offered himself as a model for imprinting; goslings followed him as if he were their parent; failed to recognize mother or other conspecifics; as adults, tended to develop social relationships with humans, not geese; some initiated courtship with humansDucklings will imprint on the first object they see, eg black box, white sphereLorenz being followed by imprinted goslingsProcess of imprinting is genetically determined; but bird learns to respond to a particular animal or objectThe ability or tendency to respond to first object seen after hatching is “innate”
12 Fox 1995Imprinting, critical periods, now known to occur at various times in the life of animals, not just in very early stagesImprinting was initially understood as a learning phenomenon of very young animals (e.g., Lorenz’ geese critical period was first two days of life)Current understanding is that similar learning processes occur in older animals, and involves a variety of functionsAspects of imprinting in young falcons
13 Song development in birds: a study of imprinting Early experiments showed song development in male white-crowned sparrows is an imprinting phenomenonTwo learning processes in the sparrow’s song developmentbird must acquire a song type by hearing an adultbird must learn to match this song by listening to itselfLater research showed variability in the processStrong stimulus (exposure to live male of another species) can overcome developmentally fixed tendency to acquire only a conspecific songSame strong stimulus resulted in longer critical period (>50 days)Sonograms of songs of white-crowned sparrows reared under three conditionsMales that heard tapes of conspecific songs before day 50 (a) learned to sing normally, months later. Males raised in soundproof chambers (b) learned only to sing primitive template of song. Males deafened after hearing tapes of conspecific song, but before beginning to practice, did not even learn the primitive template.
14 Hypothalamic-Pituitary-Gonadal Axis of Birds is Similar to that of Other Vertebrates Environmental cues, including photoperiod, songreceptorsHypothalamuspituitarybloodstreamgonadsblood stream accessory sex organs, secondary sex characters, including behaviorsDomestic Chicken, derived from the Jungle Fowl (Gallus gallus) [Galliformes]
15 Endocrine control of morphological and behavioral components of singing in male canaries Fernando Nottebohm ID’ed forebrain nuclei responsible for song learning in canariesHigh variation in size of nuclei among males based on season and number of vocalizations in repertoire; nuclei largest during breeding season, in males with most songsReduction in nucleus size may be mechanism for “erasing” unneeded songs and regeneration, for learning of new songs to take placeOne of the first demonstrations of growth and development of neurons in adult vertebratesHierarchical processing of motor program to vocalize is an important model for understanding how humans speak and learn to speak
16 Hormones and Sexual Dimorphism in Behavior and Neural Circuitry In young zebra finches, male and female song nuclei are similar; females’ nuclei undergo apoptosis, while males continue to growPreviously thought that brain gender differences arise because in females, tissue doesn’t grow, but in males, homologous tissue does growcell death in brain sexual differentiation now known or suspected in many mammalian systems -- first elucidated in songbirdsMechanism in Zebra Finchesestrogen secreted by male gonadal cells prevents neuronal death and promotes development of connections between some nuclei (estrogen is converted to a testosterone-like metabolite inside cells)experimental support; estrogen implants in young females masculinizes song control system -- induces same effects of estrogen seen in malesSignificanceinsight into brain development and neural plasticitypotential applications of mechanisms (when worked out) include inhibition of programmed cell death(Source: Kirn and DeVoogd 1989)High Vocal CenterNo. neurons in HVc (x104)Age (days after hatching)Changes in the song system of young zebra finches. The number of nerve cells in the female’s HVc, a component of the song system, declines rapidly as the males increasesHormones and Sexual Dimorphism in Behavior and Neural Circuitry
17 Song Control Centers and Functional Lateralization Nottebohm (1980) discovers functional lateralization of avian song; left hemisphere dominanceExperimental ablation of left hemisphere song centers; new centers develop in right hemisphere, function in song control; bird develops distinct song repertoireSignificance; Such functional lateralization thought to occur only in humans, where it is associated with extraordinary language abilities
18 HVc affects song discrimintation by females HVc affects song discrimintation by females. The HVc region of the female canary’s song system helps her discriminate between the song of male canaries and that of other species. After destruction of the female’s HVc, she will perform copulatory displays to tapes of white-crowned sparrows. (After Alcock 1998, Brenowitz 1991)
19 Biological RhythmsLife, lineages, evolved in 24-hour cycles of light and darkAcross kingdoms, lineages have endogenous circadian rhythms of activity -- eating, sleeping, motor patterns (e.g. treadmill), metabolic function…“Biological clocks”, the proximate mechanisms that drive circadian rhythms, are fundamentally important organizers of animal behaviorThe period (length of time of period) of circadian rhythm is entrained (set) by an environmental cue; light-dark cycle; organisms deprived of the environmental cue will continue rhythmic behavior in a free-running manner with periods that are about, but not exactly 24 hours (“circadian” = “about a day”)Period = one cycle length Phase= point on the cycleEntrainment= setting, resetting of clock, via environmental cue; drives phase advances or phase delays as well as periodicity
20 Marks indicate when mouse is running on activity wheel
21 Phylogenetic Perspective on Clocks Circadian rhythms occur throughout kingdom Animalia; Also occur in protistans, plants, fungiWithin animalia, among lineages, there are diversity in clocks, ie, evolution of diversity in “location, tissue, and presumably cell molecular mechanismsIn mammals, “master circadian clock” is located in the brain, in two nuclei dorsal to the optic chiasm; the suprachiamatic nuclei
22 Genetic underpinnings of circadian rhythms Genetic underpinnings of circadian rhythms. Many alleles of the period gene of Drosophila fruit flies exist. On the left is shown the strand of DNA that constitutes the period gene. Researchers know precisely where different mutations have occurred in this stretch of DNA. Each mutant allele has a characteristic effect on the activity patterns of fruit flies, shown on the right (dark bars represent time when the flies are active). The normal pattern of nonmutant (wild-type) flies appears at the bottom of the diagram [Baylies et al, in Alcock 1998]
23 Manipulation experiment demonstrates role of period gene in Drosophila Wildtype DNA from fruit flies can be take up in plasmids, some of which will then carry the per+ allele. The plasmids can then be collected and microinjected into the embryos of fruit flies with the pero “restoring” normal activity
24 The dimer is translocated to the nucleus where it inhibits further transcription of the per and tim genesper and tim dimerize in the cytoplasmTranscription and translation of per and tim show circadian rhythmsRates of transcription, translation, dimerization, may be cell-molecular components of the biological clock
25 Circannual RhythmsMoving Somewhere: Travelling requires tracking stimuli in the environmentTaxis: Movement towards or away from a stimulus; specific orientation. e.g. positive phototaxis of moths to outdoor lightKinesis: Random movement in response to stimulusMigration; regular movement, often circannual and two-way, over relatively long distances; presumably requires cognitive mappingPiloting: ability to move from one familiar cue to another – considered especially important in short-distance movementsOrientation: ability to follow a bearing (compass sense)Navigation: ability to set or adjust bearing and then follow it (compass sense and map sense); requires determination of present location and compass direction
26 Cues used by Birds and Animals for Orientation and Navigation Celestial CuesSun is used commonly for diurnal migrants and stars are used commonly for nocturnal migrantsIndigo Buntings and other species are known to use the North Star for orienting; compensation mechanism (clock) not needed because its apparent relative position remains unchangedBirds that use sun and other stars to orient presumably have internal clocks that allow them to compensate for apparent movement of sun or star due to rotation of the earth.Magnetic fieldMany migrating birds and other animals have the ability to detect the earth’s magnetic field and to orient themselves with respect to itGenerally, birds thatAnimals known or suspected to use Earth’s magnetic field to navigate include honeybees, some fishes and amphibians and sea turtles
27 Animal Cognition Cognition Cognitive Ethology Narrow sense: awareness, consciousnessBroad sense: ability of an animal’s nervous system to perceive, store, process and use information gathered by sensory receptorsCognitive EthologyThe study of animal cognition; focuses on links between behavioral output and the internal data processing by the nervous system that gives rise to the behaviorOne area of interest in cognitive ethology is internal representation of spatial relationships in an animal’s physical surroundings; cognitive mapsMigration Feat: Monarch butterflies of eastern North America in a remote fir forest in Mexico; the migration is over 3000 kilometers and takes from two to five generations to complete
29 Purves et al 2001dots represent pecks for foodbird is trained to seek food in the southbird with 6-hr phase advanced rhythm now seeks food in eastA pigeon placed in a circular cage from which can see the sky (not the horizon) can be trained to seek food in one direction, even when its cage is rotated between trialsPigeon is placed on altered light-dark cycle and its circadian rhythm is phase-advanced by 6 hrs. Bird is then returned to the training cage under natural skyStarlings and certain other birds have an “internal clock” they use to compensate for the sun’s apparent movement through the sky
30 Magnetite, a magnetized iron ore, has been found in the brains of some birds, but the sensory receptors birds use to detect magnetic fields have yet to be identifieidOrientation of homing pigeons is influenced by changes in magnetic field. Dots show angles at which birds flew off. Direction of home is straight up. Birds tested for two magnetic directions, neither of which affect birds on sunny days, but both do on overcast days, suggesting a back-up system.
31 Starling Migration Displacement experiments indicate that inexperienced starlings migrate by orientation (and is largely an “innate” behavior) while older birds that have migrated previously use true navigation (and modify their migration behavior through experience.