2 Social Organization of the Honey Bee Live together in groups of – individualsThere are three castes(i.e. there is division of labour):Queen: fertile femaleLays eggs that hatch into larvae- if larvae are fed a special diet, royal jelly (more protein), they will develop into queensProduce pheromones to regulate activities of the workersDrones: fertile malesWorkers: sterile femalesMost bees are workersinfertile females
3 Bee SocietyDrones only role is to mate with queen, which can lay 1500 eggs a day.Drones are only tolerated during the spring and summer when the queen mates, and are driven out at other times.Worker bees gather food, feed the queen, guard the colony, produce pheromones to help co-ordinate activities, feed larvae, secrete wax to build the hive and clean the colony.Workers change duties as they age, about half life span spent on indoor duties, then rest of time outside foragingWhen a new queen is needed, she hatches and takes her first flight, during which she is inseminated by several drones. She will then ‘swarm’ with members of the old hive and go establish a new hive.honey bee biology
4 Social Organization of the Naked Mole Rat Social structures are unusual for mammals:Naked moles live in colonies undergroundOnly the queen will reproduce with a few malesOther females are workers- tunnelers, defenders, or food gathersIf queen dies the larger female workers will fight until it is clear who the new queen will beThe sterility of the workers is not genetic but maintained by the queen, possible using pheromones.
5 How Natural Selection act at the level of the colony in the case of social organisms: Natural selection may act at the colony level rather than the individual levelMembers of the colony work for the benefit of the colony & not for themselvesCo-operation of individuals ensures survival of the colonyThe more efficient is the co-operation, the more likely the colony is to surviveExample, in naked mole rats:In the case of food shortage a worker could feed the queen but starve herselfThe queen and the worker are closely related so this behavior is likely to spread because the queen is likely to survive and pass on the genes that caused the workers behavior to the next generation.
8 Altruistic BehaviorAltruism- behavior which benefits others and involves risk or cost to the individual displaying the behaviour(Note: IB does not consider parental care to be an example of altruism).Example 1: Worker beeWorker bees dies defending colony against attacking wasp- never reproduces only looks after the colonyExample 2: Vervet monkeysmonkeys give alarm calls when predator approachesalarm calls attract attention of predator and others monkeys have more time to escapecloser the genetic relationship the less altruism involvedbenefits increase over time through survival of genes shared with recipientbehaviour might lead to an advantage for the individual displaying behaviour in the future
9 Altruistic Behavior Cont… Example 3: Vampire batsForm social groups, colonies, of unrelated individualsthey feed on fresh blood from animals such as pig, cattleif bats go without food for two days they can die of starvation.If one bat doesn’t feed, another one which has fed will regurgitate food and share. This is done regardless of whether the bats are related or not.A bat that has been fed in this way will give food another timeWhy? “You help me now, and I’ll help you later”.This is called reciprocal altruism
10 Explain the role of natural selection in the development of behaviour patterns innate behaviour patterns are inheritedanimals show variation in their behaviourbehaviour patterns are adapted to the environmentthose animals with adaptive behaviour more likely to surviveanimals which survive leave more offspring than those less adapted leading to change in allele frequencypopulation (species) starts to show more adaptive behaviourthus the population has evolved
11 Evolution of Altruistic Behaviour organism expends time & energy in caring for other unrelated members of the same speciessuch animals put themselves at risk or disadvantage for the good of other members of the species, such actions increase another individual’s number of offspring at cost to one’s own reproductionclose kin share allelesthe adaptive significance of altruism is to increase frequency of alleles shared in common by members of the speciesaltruism provides genetic advantages in kin by promoting survival and reproduction within speciesaltruistic behaviour towards non-relatives may allow selection of alleles responsible for the behaviour to be perpetuatedsome argue no true altruism as organism benefits either directly or indirectly in the future - reciprocal altruism ?
12 Foraging Behavior‘foraging’ refers to the processes of searching for, obtaining, and then consuming food.food is generally rarely distributed uniformly, and when located, different sources may be of different qualitiesconsequently, foraging animals need to optimise the return on their investment of time and energy in obtaining foodnatural selection will favour strategies that minimise the costs of the search and maximise the benefitsforaging Theory suggests that the food choice of the animal will maximise the energy obtained
13 Bluegill sunfish foraging for Daphnia Bluegill fish and DaphniaFish will choose largest prey when given a choice.In nature they choose the prey that appears the largestWhen prey is abundant they choose the largest, when prey is scarce they choose one that may be smaller but is closer so appears larger.More profitable to catch the closer than larger fish
17 Foraging by the honey bee Foraging for nectar and pollen is the chief duty of worker bees at a later stage in their working life.First, individual worker bee surveys for feeding sites & report back to the main body of workers in the hive.Through waggle dance, worker honey bee communicates the location of new food sources to the other workers in the colonythe waggle dance optimises food intake by the hive community
18 Mate Selection and Exaggerated Traits in animal species that reproduce sexually, the quality of the mate may be critical to reproductive successanimals seldom mate indiscriminately – various mechanisms ensure some selectivity in the sexual processsexual selection is the struggle between individuals of one sex (usually males) for the possession of access to individuals of the opposite sex.the outcome for a loser of this struggle is few or no offspringvictory in the struggle may depend on the use made of special features of structure or behaviour which are geneticthe long-term outcome has been the evolution of exaggerated traits that draw attention to a potential mate and markedly increase the possibility of reproductive success.
19 Mate Selection and Exaggerated Traits: Females choose their mates:Ones with best genesOnes with ornaments (easier for predators) must have good genes to surviveMales need to attract mate:Must have something that grabs her attentionMales may fight for dominance:Dominant male reproducesBoth males may get harmed during the fight
20 Rhythmical variations in activity in animals rhythmical behaviour patterns are common in animalsthey including daily (circadian) & annual rhythmsthese patterns have adaptive value, – aiding survival of the organisms concernedcircadian rhythms; animals are active for only a part of the 24-hour cycleannual rhythms; animals produce young ones in a season favourable for rearing and feeding
21 Rhythmical Variations Daily or yearly changes in activityHummingbirds- slow down metabolism at night in order to save energy and egg-laying in springValue of Rhythmical Variations:Coral- Mass spawning at same time for males and females- best chance of reproductionDeer- fertile period is in November so babies are born in springRoe deer- fertile in summer when healthy and the embryo “floats” in the uterus and has little growth until December when it attached and has normal growth
22 Revision QuestionsDescribe the social organization of honey bee colonies.Outline how natural selection may act at the level of the colony in the case of social organisms.Discuss the evolution of altruistic behaviour using two non-human examples.Outline two examples of how foraging behaviour optimizes food intakeUsing two named examples, outline a rhythmical behaviour pattern with an adaptive value.Explain how mate selection can lead to exaggerated traits