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Further studies of behaviour HL only E.6.1 Describe the social organization of honey bee colonies and one other nonhuman example Studies innate in nature • Automatic responses to stimuli which are controlled by genes and are therefore subject to natural selection • Populations tend to produce more offspring than the environment can support • Variations within populations can be selected for or against • INNATE BEHAVIOUR become optimised over time The Secret Life of Honeybees Live above ground trees Make wax combs – store honey Cells storing honey & rearing young • Queen • Workers • Drones Lay eggs Sterile female Males for mating All female, nonreproductive Go through series of roles in order: young bee, nurse, builder, guard, honeymaker Live for around 30 days Feed queen and drones Drone Workers Queen Produce eggs Flies only to mate & swarm Controls colony activity by scent Mates with many males at one time & stores sperm Lays thousands of eggs Cuts down on egg production if food supplies are scarce Haploid males Only function is to mate Mate in the air and die soon after Bee organization influenced by diet • Unfertilized eggs = male no matter what they eat • Fertilized eggs + type of food = queen or worker • Larvae fed royal jelly first few days – Then switch to pollen + honey = workers – Royal jelly continues = new queen Control with phermones • Inhibit ovarian development in workers • Workers lick it off queens body while eating & pass it to other workers Bee communication • Chemical in tip of abdomen is used to identify the source of nectar or water • Some bees scout, find nectar and do a waggle dance – direction & distance • Chemical from the mouth identifies danger to the colony Social organization - chimps • Work of Jane Goodall – ethologist • Community – highest order – 40-60 members – Party • • • • • Up to 5 members May be all males A family unit Nursery unit Depends on food supply Social hierarchy • Highest = male, age 20-26 – Dominance determined • physical features • Fighting ability • Females = linked with age • Males have strong social bonds – Related to each other – Stay in same community – Females may migrate Roles • Male bonding leads to cooperative behaviour E. 6. 2 Outline how natural selection may act at the level of the colony in case of social organisms Natural Selection at the colony level • It would seem worker bee behaviour would not be promoted by natural selection • Natural selection = most well-adapted worker will survive & reproduce • However, workers don’t reproduce • The gene causing the behaviour of the worker should be eliminated from the population Natural Selection – colony level • Natural selection is acting on the colony as a whole • Genes selected for: – Promote social organization – Pheromones to control the behaviour of workers – Behaviour of finding nectar and making wax By chance who – Taking care of the young gets fed the royal jelly Naked Mole Rat: colony living • Heterocephalus glaber • Blind • Underground colonies – One queen – Small number of reproductive males – Others don’t mate Naked Mole Rats • Intraspecific competition is fierce and bloody when the queen dies. • Other females compete to take her place • Social status depends on reproductive ability • Non-reproductive individuals act altruistically to promote the survival & reproductive fitness of the queen and her offspring Natural Selection at the colony level • A colony of individuals with set roles (castes) displays emergent properties • A whole of a colony is more that the sum of its parts E.6.3 Discuss the evolution of altruistic behaviour using two non-human examples Altruistic Behaviour • Promotes the reproductive fitness of another individual at considerable cost to oneself Honeybee guards sacrifice their own life for the colony’s survival. How has altruism evolved? Kin selection Reciprocal altruism • Closely related individuals are promoted thus ensuring the survival of shared genes (decrease in fitness of the altruist) • Helping another may be returned in the future, ensuring the survival of oneself and thus aiding reproductive success Kin Selection Ant Colonies Males are haploid, females are diploid Diploid females are 75% similar genetically (chromosomes from males are not subject to independent assortment, therefore are all identical) Animal communication I am mostly likely going to be killed Kin Selection • Naked Mole Rats – Main predator – snakes – Snake attack • Queen sends workers to attack snake • Workers sacrificed so queen and young live Reciprocal Altruism • “You scratch my back, I’ll scratch yours” Vampire bats • Hematophages – Feed on 50% of their body weight every 2436 hours • Blood-sharing – Unrelated bats can share blood – Typically between females – Ensures survival of own offspring if needed one’s E. 6. 4 Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia Foraging – the act of searching for, chasing, capturing, killing & consuming food Benefit • Foraging results in food; a benefit in terms of energy Cost • Foraging takes energy; there is a cost in terms of time and energy Cost-Benefit Analysis • As long as the benefit of energy outweighs the energetic and time cost expended, the foraging strategy has a positive impact on the individual’s reproductive fitness • If a foraging strategy has an overall cost, it will harm the individual’s reproductive fitness – and therefore have a deleterious effect. It will likely be lost through natural selection Optimal foraging Bluegill Optimal Foraging Acanthaster planci Crown of Thorns starfish Widespread damage to coral reef ecosystems Eats coral polyps Patch residence time E.6. 5 Explain how mate selection can lead to exaggerated tails Mate Selection Small Tail Large Tail Healthiest bird Size Matters Mate Selection • Females will select mate based on exaggerated trait • Exaggerated trait = advertisement of reproductive fitness, not adaptation for survival • Subject to natural selection bc. they are physical or behavioural and genetic in nature Mate selection • Competition between males for mates can be fierce • Through decent with modification, these traits become ever more elaborate and attractive • Can drive speciation E.6.6 State that animals show rhythmical variations in activity Rhythmical Behaviour Seasonal Changes Daily (Circadian) changes Monthly (lunar) changes • Seasonal phenotypes • Changes in day length, food availability, etc • Strong, indogenous component • Exogenous cues are important • Phases of the moon – light intensity • Tidal rhythms E.6.7 Outline two examples illustrating the adaptive value of rhythemical behaviour patterns Rhythmical Behaviour Once a year, coral release millions of gametes in a synchronized mass spawning ritual. Exact cues are unknown (water temperature, lunar cycle, hours of daylight?) Lunar cycles Synchronized nesting – leads to increase chance of survival of hatchlings Lunar Cycles • Lunar cycles control turtle migration • Mass egg laying at high tide between last and first quarters of the moon • Tide is weakest • Less egg exposure to predators Seasonal Behaviour • Remember how photoperiodism controls flowering in angiosperms? Well, think up the food chain. • Seasonal behaviour includes: – – – – Waking from hibernation Reproductive seasons Migration Spawning seasons Climate change impacts seasonal cycles • Patterns of behaviour are innate in nature and thus subject to natural selection • Cycles have been optimized through evolution, with some small variation within populations • Climate change has a negative effect on temperature and coincides with food or resource availability Circadian Rhythms • Internal ‘Body Clocks’ • Influenced by light-dark cycles – – – – Genetic in nature Optimized for 24 hour dark-light cycles Healthy function of metabolism Sleeping/feeding patterns Circadian Rhythm