A system
A flotilla.
A school of fish.
A group of lions is called a pride.
A band.
If you mean "group", it is a covey.
A group of whales are commonly called a pod, or a school.
A group of horses can either be called a band or a herd.
A group of chickens is called a flock, kinda like other birds. :)
Ants.
A Long Line Of Ants is called an Army of Ants
genuinely a cluster, but some have developed their own names for it.