Units 1 & 2: Introduction to Ethology PDF

UNIT 1 INTRODUCTION TO ETHOLOGY UNIT 2 BASIC CONCEPTS AND SCIENTIFIC TERMS UNITS 1 & 2 – Introduction to Ethology. Basic concepts and scientific terms Definitions. History of Ethology and aims of study. New lines of study. Behavioral ecology and evolution. Methodologies fo...

UNIT 1 INTRODUCTION TO ETHOLOGY UNIT 2 BASIC CONCEPTS AND SCIENTIFIC TERMS UNITS 1 & 2 – Introduction to Ethology. Basic concepts and scientific terms Definitions. History of Ethology and aims of study. New lines of study. Behavioral ecology and evolution. Methodologies for the study of animal behaviour. Four levels to explain animal behaviour: Causation, Development, Function and Evolution Proximate and ultimate causes. Natural selection, individual selection and group selection. Fitness. Life histories. Trade-offs. Adaptation. Stable Evolutionary strategies. Genetic basis of animal behaviour. Ethology Ethology is the scientific study of animal behavior, particularly in natural environments. The modern scientific discipline of Behavioral ecology extends observations of animal behavior by studying: – how such behavior is controlled – how it develops, evolves, and contributes to survival and reproductive success. – Summarizing: is the study of the ecological and evolutionary basis for animal behavior Evolution: The Basics What is a BEHAVIOUR? is the nervous system’s response to a stimulus and is carried out by the muscular or the hormonal system What is Evolution? – is a change of gene frequencies within a population (or species) over time – Individuals do not evolve, populations evolve – Focus on gene pool, collective What is an allele? – A variant of a gene or trait Examples of variation in traits – Eye color (blue, brown, hazel, green) – Timing of shell-removal for black-headed gulls (45, 50, 60 minutes after hatching, etc.) Evolution: The Basics If frequency of particular variants of traits changes over time = EVOLUTION Evolution: The Basics Adaptation: Individuals of a species have certain characteristics that enable an organism to thrive (= grow healthy) in a given environment. Could be a – Structure – Behavior – Physiological process Adaptations help an organism to survive and reproduce: maintain or increase fitness in a given environmental conditions. Example Structural Adaptation Structural Adaptation – a physical trait that helps an organism to survive or reproduce (EX. the sharp teeth of a lion, the spines of a cactus) Example Behavioral Adaptation Behavioral Adaptation – a behavioral trait that helps an organism to survive or reproduce (EX. plover birds faking injury to lure predators away from nest)  Can you see some adaptations? http://www.eveboo.com/wp-content/uploads/2013/05/snow-wolf-wallpaper.jpg Can you see some adaptations? http://i.imgur.com/HZTh8ZG.jpg Evolution: How do adaptation develop? They are a result of a gradual change of characteristics over time A variation that helps an individual in a population (= increase fitness) is likely to be passed on from survivor to survivor Some variations help and some do not, not all variations become adaptations! Fitness: average contribution to the gene pool of the next generation that is made by individuals of the specified genotype or phenotype – Survival – Reproductive success (acquire mate, rear sons, …)  Why is variation so important? Because the environment changes! The more variation within a species, the more likely it will survive. If everyone is the same, they are all vulnerable to the same environmental changes (or diseases) Example: Which moth will the bird catch?  Where do variations come from? 1. MUTATIONS – Mutations are genetic changes that happen in DNA – Occur from mistakes that happen when DNA is being copied – For example: Your DNA has about 175 mutations compared to your parents.  Harmful: Cause diseases or deformities  Helpful: organism is better able to survive  Neutral: organism is unaffected  Where do variations come from? 2. SEXUAL RECOMBINATION of DNA – During crossing over and fertilization – Produces variations that make adaptation possible – Sexual reproduction results in unique combinations of genes every generation  Where do variations come from? 3. GENE FLOW – Exchange of genes between populations Can you explain me this slide? Can you explain me this slide? Can you explain me this slide? Can you explain me this slide? Evolution: The Basics Inclusive fitness (Hamilton): direct fitness + indirect fitness Direct fitness is personal reproduction Indirect fitness is the additional reproduction of relatives that is made possible by an individual’s actions Behavior that results in indirect fitness gains is favored by kin selection Kin selection: A form of selection in which alleles differ in their rate of propagation because they influence the survival of kin who carry the same allele Evolution: Natural selection as a force of evolution  Natural selection as a force of evolution What is Darwin’s natural selection? The differential success (survival and reproduction) of individuals within the population that results from their interaction with their environment. “Survival of fittest, elimination of less-adapted individual” Conditions (assumptions): 1. There is variation in populations. 2. Variation is heritable. 3. In every generation some organisms are more successful at surviving and reproducing than others. Survival and reproduction are not random, but are related to variation among individuals. Organisms with best characteristics are ‘naturally selected.’ If these conditions are met then the population will change from one generation to the next. Evolution will occur  Natural selection as a force of evolution In any population of organisms there is natural variation. Some of these variations will allow the organisms possessing them to survive and reproduce better than those without these particular traits The successful traits will spread through the population. This change in the frequency of alleles in the population is evolution. Individuals do not evolve; populations evolve! Evolution is measured as changes in relative proportions of heritable variations in a population over several generations. Natural selection – IMPORTANT POINTS Natural selection can only work on heritable traits. – Acquired traits are not heritable and are not subject to natural selection. Environmental factors are variable. – A trait that is beneficial in one place or time may be detrimental in another place or time. When natural selection is occurring, some individuals are having better reproductive success than others. – Alleles are being passed to the next generation in frequencies that are different from the current generation. Darwin’s Theory of Natural Selection : 4-step process Overproduction – there are more organisms born than the environment can support Variation – organisms in a population are not all the same (variation); each individual has a unique combination of inherited traits (adaptation) Competition – organisms compete with other members of the population for resources (food, shelter, water, mates) Selection (Survival of the Fittest) –- organisms with best adaptations are more successful than organisms without these adaptations (live longer and/or reproduce more) Natural selection: 4-step process Passing of Traits – genes that cause adaptations are passed from one generation to the next, changing the gene pool and causing changes in the overall traits of the species (beneficial adaptations appear more frequently) Example GIRAFFES 1. More giraffes are born than the environment can support 2. Giraffes compete for resources 3. The giraffes with the longest necks have a survival advantage, so they survive longer and reproduce more 4. The genes causing the longest necks are passed on more than the other neck genes, changing the giraffe gene pool and causing the average neck length of giraffes to increase from one generation to the next Evidence of natural selection Evolution of beak shape in Finches. Peter and Rosemary Grant’s (and colleagues) work on Medium Ground Finches Geospiza fortis. 40-ha Daphne Major island Evidence of Natural Selection Is there a phenotypic variation in beak size?  Is variation in beak size correlated with variation in fitness? In 1978, there was a severe drought, small seeds declined more than large seeds. Small beak birds have difficult to find seeds, and suffered heavy mortality, especially females. Evidence of Natural Selection Beak size evolves post-drought pre-drought Conclusion: Nature selection indeed caused evolution in beak size Types of Natural Selection Variation of species characteristics occurs along a spectrum ranging from one extreme to another EX. Height in humans, from very short to very tall 3 types of NS: Stabilizing, Disruptive & Directional Types of natural selection Directional Selection: Individuals at one end of the variation curve have increased fitness. Selects in the direction of one extreme phenotype An extreme phenotype (very long or very short etc.) is a favorable adaptation. Types of natural selection Stabilizing Selection: Individuals in the middle of the variation curve have increased fitness. Extreme phenotypes are unfavorable. Average phenotype is a favorable adaptation. Operates most of the time in populations Ex. Mouse size: too big use too much energy to keep warm; too small can’t burrow. Average is just right Types of natural selection Disruptive Selection: Individuals at both ends of the variation curve have increased fitness 2 opposite extreme phenotypes are favorable over average phenotype Ex. Some crabs show a continuous range of color from light tan to dark brown. The light tan provides camouflage in the sand. Dark brown provide camouflage in mud. Colors in between – no camouflage Over time this could lead to speciation Types of natural selection Heritability is an essential feature of Natural Selection Heritability: individual’s characteristics are passed from one generation to the next. Measured as proportion of the variation in a trait in a population that is due to variation in genes. Mendel’s genetics and inheritance BEHAVIOUR = genes + environment Whether an animal CAN exhibit a particular behaviour is determined by genes Whether an animal DOES exhibit this behaviour can be dependent on environment. – An animal may not exhibit a possible behaviour in certain environments What are genes? Genes: discrete subunit of chromosome, carry genetic information Chromosomes: the threadlike structures where DNA is contained DNA: Deoxyribonucleric acid. All DNA is composed of the same 4 nucleotide (ATGC), differ in sequence. Alleles: alternate forms of a gene (A, a). Locus: the position of an allele occupies on a chromosome Homozygous (AA, aa) vs heterozygous (Aa) Dominance (A vs a), incomplete dominance (Aa shows different trait to AA or aa) Genetic Basis of Behavior A master regulatory gene can control many behaviors – For example, a single gene controls many behaviors of the male fruit fly courtship ritual Multiple independent genes can contribute to a single behavior – For example, in green lacewings, the courtship song is unique to each species; multiple independent genes govern different components of the courtship song 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 Responding to a Changing Environment 1. Physiological Responses - changing the functioning of the body - acclimation (dilating capillaries to release heat) 2. Morphological Responses - changing the anatomy (structure) of the body - growing thicker fur or change in fur color in winter 3. Behavioral Responses - changing behavior to adapt to the change - moving to a more favorable location - cooperative behavior - agonistic behavior when threatened Introduction to Ethology: Historical Perspectives When did the study of animal behavior emerge? – As far back as recorded history!!! (cave paintings; petroglyphs) – Animals were sources of FOOD and FEAR Introduction to Ethology: Historical Perspectives Aristotle (384-322 B.C.) – First written records of mutualism, tool use, and brood parasitism Introduction to Ethology: Historical Perspectives Charles Darwin (1809-1882) – Darwin’s key insight for ethology: behavioral traits are a part of an organisms evolved phenotype – Phenotype = Morphology + Physiology + Behavior Darwin’s Legacy to Ethology and Comparative Psychology Charles Darwin (1809-1882) – Natural history – Communication – Sexual selection and courtship – Comparative cognition – Emotion – Instinct and behavioral development; – Inheritance of behavior – Phylogeny of behavior – Sociobiology and behavioral ecology – Applied animal behavior, animal welfare, and conservation Introduction to Ethology: Historical Perspectives Introduction to Ethology: Historical Perspectives COMPARISON OF ETHOLOGY AND PSYCHOLOGY Ethology ----------------------------------- Psychology - origins in natural history - origins in physiology & medicine -early focus -early focus - understanding - understanding causation adaptive value of and motivation of human behaviour in the behaviour using animal wild models - field-based - laboratory-based - initially more observational - initially more empirical MODERN ANIMAL BEHAVIOR Aims and Methods of Ethology Tinbergen’s Four Questions (The 4 Why’s) Animal Behaviour can be explained in terms of: – Causation – Development – Function – Evolution (Tinbergen 1963) Tinbergen’s Four Questions (The 4 Why’s) Why is this bird singing? Tinbergen’s Four Questions (The 4 Why’s) Why is this bird singing? (This is actually 4 questions) 1. CAUSATION. What causes this bird to sing (or: what are the anatomical and physiological mechanisms underlying the behaviour)? 2. DEVELOPMENT. How did this behaviour develop in the lifetime of the bird? How does the animal’s experience during growth and development influence the response? 3. FUNCTION. What is it singing for (territory, mates) How does the behavior aid survival and reproduction? 4. EVOLUTION. How did this behaviour evolve? What is the behavior’s evolutionary history? Proximate vs. Ultimate Causes Two classes of e scientific questions about behavior: – Those that focus on the immediate stimulus and mechanism for the behavior. PROXIMATE – Those that explore how the behavior contributes to survival and reproduction (= fitness). ULTIMATE Behavioral ecology integrates proximate and ultimate explanations for animal behavior Proximate vs. Ultimate Causes PROXIMATE, or “how”, questions about behavior focus on the environmental stimuli that trigger a behavior. – “how” a behavior occurs or is modified? – Focus on the genetic, physiological, and anatomical mechanisms underlying a behavioral act. – including Tinbergen’s questions 1 and 2 ULTIMATE, or “why”, questions about behavior address the evolutionary significance of a behavior. – “why” a behavior occurs in the context of natural selection? – including Tinbergen’s questions 3 and 4 Proximate and Ultimate Questions Proximate questions focus on the environmental stimuli that trigger behavior – Physiological & genetic mechanisms of behavior – How does a behavior happen? Ultimate questions focus on the evolutionary significance of a behavior – Why does a behavior happen? – What is the evolutionary benefit of the behavior? Proximate and Ultimate Questions Levels of Analysis in Ethology Proximate Causes Ultimate Causes Genetic/Developmental Sensory/Motor Historical Selective Mechanisms Mechanisms Pathways Processes -nervous systems for -evolutionary -adaptive context ? -effects of heredity -development of sensory- stimulus detection development motor systems -hormone systems for of a trait -gene-environment adjusting response interactions levels -muscles for carrying out responses How? Why? Control of Behavior: Innate and Learning behavior Genes and the environment both influence behavior Innate behavior – developmentally fixed – regardless (independent) of the environment – under strong genetic influence (ex. agonistic behavior) Learned behavior – cognitive development – Learning is the modification of behavior based on specific experiences. – change with experience & environment (ex. Mother bears teach their cubs about hunting, berry picking, fishing, and the best places to find tasty grubs) – Learned behaviors range from very simple to very complex Fixed Action Pattern (FAP) FIXED ACTION PATTERN: Sequence of unlearned (innate) behavioural acts that is unchangeable and usually carried to completion once initiated – Fixed action pattern is stimulated by a sign stimulus (external sensory stimulus) – Many animals only use a relatively small subset of sensory information to trigger behaviour, humans are more complex Fixed Action Pattern (FAP) = INSTICT  Lorenz and Tinbergen (1938) examined egg-rolling behavior in the greylag goose Fixed Action Patterns In male sticklebacks, the sign stimulus for attack behavior, is the red underside of an intruder. (a) A male three-spined stickleback fish shows its red underside. Fixed Action Pattern (FAP) = INSTICT Fixed Action Patterns Male English robins will attack a bundle of red feathers placed in their territory, but will ignore a stuffed juvenile (no red). Expression of a Fixed Action Pattern Expression of a Fixed Action Pattern Expression of a Fixed Action Pattern Do humans express Fixed Action Patterns? IMPRINTING Imprinting is a type of behavior that includes both learning and innate components and is irreversible – limited phase early in an animal’s development, is the only time certain behaviors can be learned (critical period) – Incubator-hatched goslings imprinted on scientist (Konrad Lorenz) during first few hours of life and followed him – great book: King Solomon’s Ring IMPRINTING Konrad Lorenz showed that when baby geese spent the first few hours of their life with him, they imprinted on him as their parent. IMPRINTING distinguished from other types of learning by a sensitive period – a limited phase in an animal’s development that is the only time when certain behaviors can be learned. Imprint of “mother” – important for eliciting care, developing species identity – during sensitive period can be experimentally imprinted on the wrong mother. – imprinting in programs to save the whooping crane from extinction Imprinting Young male white-crowned sparrows learn their song by listening to their father. – A bird raised in isolation will have an abnormal song. If he hears a recording of the song during a critical period, he will learn it – even the local dialect. – He can only learn the song of his species. Imprinting Fixed Action Patterns Life-history traits What is “life history”? – A typical life history of any animal Reproduction maturity ceases Birth Death Reproduction Life-history traits From a “fitness” perspective, there are only 2 important events in life: reproduction and death. Traits that determine the timing and details of these events are termed life history characters: – Age at first reproduction (time to maturity) – Total life span – Mode and frequency of reproduction – Fecundity (N of offspring produced) – Parental care – Viability of off-springs Life-history traits and Trade-offs Organisms have limited time, energy, and nutrients at their disposal Biological processes take time. An individual growing to a large size before maturing risks dying from disease or other causes before ever reproducing Each individual is faced with the problem of allocation of time and resources: Energy devoted to one function (i.e. growth or tissue repair), cannot be devoted to other functions (i.e. reproduction) Fundamental trade-offs involving energy and time mean that every organism’s life history is an evolutionary compromise. Life-history traits and Trade-offs Simplest, most general life-history tradeoff Life-history traits and Trade-offs Natural selection shapes the timing of life histories, and patterns of allocation to growth, maintenance, and reproduction throughout the lifespan Life-history traits and Trade-offs Evolutionarily Stable Strategy (ESS) A strategy which, if adopted by a population in a given environment, it cannot be displaced by any alternative strategy that is initially rare. Adapted from Maynard Smith (1972) as an equilibrium refinement of the Nash equilibrium: once it is fixed in a population, natural selection alone is sufficient to prevent alternative (mutant) strategies from invading successfully. Widely used in behavioural ecology and economics, and has been used in anthropology, evolutionary psychology, philosophy, and political science.  Ecology Population Biology Evolutionary Biology Genetics Sociobiology Ethology Endocrinology Neurophysiology Physiology