If a zebra is attacked, its family will come to its defense, circling the wounded zebra and attempting to drive off predators.
The above defeats the concept and definition of 'Survival of the Fittest'. Charles Darwin believed there is no such thing as altruism, all creatures look out for 'self' alone and left to themselves each species or animal is responsible for its own survival; this includes help from its own family. While he accepted certain natural characteristics [long necks, strong beaks, better sight at night etc.] helped specific animals develop and mature as survivors while those with lesser dispositions died out, he left out families and communitarian responsibilities altogether.
He believed animals were incapable of 'social intelligence' [training of other animals (ants), interaction through play (dolphins), use of twigs as tools (monkeys) and the need to assign and fulfil responsibilities on each member of a community to ensure a society runs smoothly (bees) other than 'co ordination' (follow the leader).
Charles Darwin also never observed or may have come across defence of communities either. Meerkats, ants, termites and other insects/animals have 'functionaries' devoted to the security of their territories from predatory enemies.
The last two species have in addition to sentries on guard duty, organised armies as well, declare war and take slaves [other ants and termites from different colonies]; in short the minor formation and social design of a primitive ancient human state.