It can manifest in the appearance of individuals within a group whose behavior -LRB- and sometimes anatomy -RRB- is modified for group defense , including self-sacrifice -LRB- `` altruism '' -RRB- .

It most commonly manifests in the appearance of individuals within a group whose behavior -LRB- and sometimes anatomy -RRB- is modified for group defense , including self-sacrifice -LRB- `` altruism '' -RRB- .
