E6- Further Studies of Behaviour

Pp 499 - 505

Social Organization of the Honey BeeLive together in groups of

20 000–80 000 individualsThere are three castes(i.e.

there is division of labour):Queen: fertile female

Lays eggs that hatch into larvae- if larvae are fed a special diet, royal jelly (more protein), they will develop into queens

Produce pheromones to regulate activities of the workers

Drones: fertile malesWorkers: sterile females

Most bees are workers infertile females

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 foraging

When 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

Social Organization of the Naked Mole RatSocial 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 gathers

If queen dies the larger female workers will fight until it is clear who the new queen will be

The sterility of the workers is not genetic but maintained by the queen, possible using pheromones.

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 level

Members of the colony work for the benefit of the colony & not for themselves

Co-operation of individuals ensures survival of the colony

The more efficient is the co-operation, the more likely the colony is to survive

Example, in naked mole rats: In the case of food shortage a

worker could feed the queen but starve herself

The 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.

Altruistic Behaviour

Altruistic Behaviour - Animation

Altruistic Behavior Altruism- 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 bee Worker bees dies defending colony against

attacking wasp- never reproduces only looks after the colony

Example 2: Vervet monkeys monkeys give alarm calls when predator

approaches alarm calls attract attention of predator and

others monkeys have more time to escape closer the genetic relationship the less

altruism involved benefits increase over time through survival

of genes shared with recipient behaviour might lead to an advantage for

the individual displaying behaviour in the future

Altruistic Behavior Cont…Example 3: Vampire bats

Form social groups, colonies, of unrelated individuals

they feed on fresh blood from animals such as pig, cattle

if 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 time

Why? “You help me now, and I’ll help you later”.

This is called reciprocal altruism

Explain the role of natural selection in the development of behaviour patternsinnate behaviour

patterns are inherited

animals show variation in their behaviour

behaviour patterns are adapted to the environment

those animals with adaptive behaviour more likely to survive

animals which survive leave more offspring than those less adapted leading to change in allele frequency

population (species) starts to show more adaptive behaviour

thus the population has evolved

Evolution of Altruistic Behaviour organism expends time & energy in

caring for other unrelated members of the same species

such 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 reproduction

close kin share alleles the adaptive significance of altruism is

to increase frequency of alleles shared in common by members of the species

altruism provides genetic advantages in kin by promoting survival and reproduction within species

altruistic behaviour towards non-relatives may allow selection of alleles responsible for the behaviour to be perpetuated

some argue no true altruism as organism benefits either directly or indirectly in the future - reciprocal altruism ?

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 qualities

consequently, foraging animals need to optimise the return on their investment of time and energy in obtaining food

natural selection will favour strategies that minimise the costs of the search and maximise the benefits

foraging Theory suggests that the food choice of the animal will maximise the energy obtained

Bluegill sunfish foraging for DaphniaBluegill fish and

DaphniaFish will choose largest

prey when given a choice.

In nature they choose the prey that appears the largest When 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

Bluegill sunfish foraging Animation

In bluegill sunfish, Prey selection behaviour is related to prey density

Foraging by the honey bee

Foraging by the honey beeForaging 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 colony

the waggle dance optimises food intake by the hive community

Mate Selection and Exaggerated Traits in animal species that reproduce

sexually, the quality of the mate may be critical to reproductive success

animals seldom mate indiscriminately – various mechanisms ensure some selectivity in the sexual process

sexual 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 offspring

victory in the struggle may depend on the use made of special features of structure or behaviour which are genetic

the 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.

Mate Selection and Exaggerated Traits:Females choose their

mates:Ones with best genesOnes with ornaments

(easier for predators) must have good genes to survive

Males 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

Rhythmical variations in activity in animalsrhythmical behaviour

patterns are common in animals

they including daily (circadian) & annual rhythms

these patterns have adaptive value, – aiding survival of the organisms concerned

circadian rhythms; animals are active for only a part of the 24-hour cycle

annual rhythms; animals produce young ones in a season favourable for rearing and feeding

Rhythmical VariationsDaily or yearly changes in activity

Hummingbirds- slow down metabolism at night in order to save energy and egg-laying in spring

Value of Rhythmical Variations: Coral- Mass spawning at same time

for males and females- best chance of reproduction

Deer- fertile period is in November so babies are born in spring

Roe 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

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 intake

Using two named examples, outline a rhythmical behaviour pattern with an adaptive value.

Explain how mate selection can lead to exaggerated traits