There are many different types of animal groups. Some are temporary, while some are extremely stable. Not all groups involve cooperation. At the other extreme are social groups in which the individual sacrifices for the good of the larger group. The latter form of organization is extremely rare.
Sociobiology is the systematic study of all forms of social behavior, in animals and humans.
The major method used by sociobiologists is the comparative study of different species of animals and cross-cultural studies of different human groups. These data are then viewed in light of natural selection and used to generate hypotheses about the origins of specific behaviors. Such studies are difficult. The hypotheses generated are often controversial. Colonial invertebrates, such as the Portuguese man o' war, illustrate the simplest type of association in which all members of a colony are genetically identical.