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.