Unit 3 (KA6) Flashcards
Advantages of social groups
Protection - safety in numbers
Increased chance of finding food and a mate
Get help with raising young
Social behaviour
Animals react to social signals given by other individuals.
Members of social groups have behavioural adaptations to promote group cohesion : social hierarchies, co-operative hunting, social defence mechanisms and altruism.
Social hierarchy
Members of a social group are arranged as a graded order of rank, maintained by aggression between individuals.
A high ranking individual dominates others of a lower rank, which are subordinate to it.
Dominant individuals get first choice of food, sleeping areas and mates.
Dominant behaviour
Dominance is displayed using social signals eg. pecking in chickens, ritualised threat gestures in wolves (bared teeth, raised hackles).
Submissive behaviour
Displayed by subordinate animals to acknowledge the status of high ranking individuals. eg. cowering or rolling in wolves.
Advantages of social hierarchies
Aggression becomes ritualised
Conflict is reduced, avoiding injury.
Energy is conserved.
Experienced leadership is guaranteed.
The most powerful animals pass their superior alleles on to the next generation.
Co-operative hunting
Co-operation between individuals within a social group is used when hunting prey.
eg. orcas hunting seals, lionesses ambush strategy, wolf packs
The food reward must be greater than when hunting alone, considering that subordinates will get smaller share.
Advantages of co-operative hunting
Increases hunting success
Reduces chance of injury
All members of the social group benefit, as food is shared, including with young and injured animals.
Larger prey can be killed, compared to hunting alone
Social mechanisms for defence
Shoaling (fish) and flocking (birds) rely on ‘safety in numbers’ and alarm calls to alert others to the presence of predators.
It is hard for a predator to target one individual in a large group.
Specialised defensive formations
Musk oxen encircle their young, horns facing outwards to defend them against wolves.
Quails roost in circles facing outwards to watch for predators, they fly upwards when startled to confuse the predator.
Baboons travel in troops, with high ranking individuals and young in the centre, expendable subordinate males to the outside.
Altruism
Animals behave in a way that is disadvantageous/harmful to themselves, but benefits others.
There are 2 types of altruism : reciprocal altruism and kin selection.
Reciprocal altruism
One individual helps another on the understanding that the favour will be returned in the future.
Members of the social group must be able to recognise each other and ‘keep score’ of favours owed.
The benefit to the recipient outweighs the cost to the donor.
eg. grooming in apes, blood sharing in vampire bats, prisoner’s dilemma
Kin selection
An individual will put itself at risk to save the lives of its close relatives, with whom it shares many genes.
eg. warning calls in birds
Donors benefit indirectly, as copies of shared genes survive.
Coefficient of relatedness
Describes how many genes are shared eg. parent/child = 0.5
Social insects
An example of kin selection.
Found in bees, ants, wasps and termites.
There is division of labour within the colony, with most work carried out by sterile females.
Workers gather food, clean and defend the colony and raise the offspring of the queen.
The sterile workers co-operate to raise their close relatives, increasing the survival rates of shared genes.
