Transcript Document

27.4 Social Behavior
KEY CONCEPT
Social behaviors enhance the benefits of living in a
group.
27.4 Social Behavior
Living in groups also has benefits and costs.
• Social behaviors evolve when the benefits of group living
outweigh its costs.
– benefits: improved
foraging, reproductive
assistance, reduced
chance of predation
– costs: increased
visibility, competition,
disease contraction
• Group living requires learning social structure and
membership.
27.4 Social Behavior
Social behaviors are interactions between members of the
same or different species.
• Animals use communication to keep in contact.
– visual
– sound
– touch
– chemical
27.4 Social Behavior
• Courtship displays are used to evaluate the fitness of a
potential mate.
• Defensive behaviors are used to protect the individual
and/or the group.
27.4 Social Behavior
Some behaviors benefit other group members at a cost to
the individual performing them.
• There are many types of helpful social behavior.
– cooperation
– reciprocity
– altruism
27.4 Social Behavior
• In altruism, an individual reduces its own fitness to help
other members of its social group.
– inclusive fitness
– kin selection
27.4 Social Behavior
Eusocial behavior is an example of extreme altruism.
• Eusocial species live in large groups of mostly
nonreproductive individuals.
– haplodiploid species: social insects (wasps, bees, ants)
Queen
Minor worker
Major worker
– diploid species: termites, snapping shrimp, naked mole
rats
• Eusocial behaviors likely evolve by kin selection.