memory

An observable fact or event that involves human society is known as a social phenomenon. This includes anything that influences the behavior of each other in a society.

Fish is a vertebrate that lives in water while tadpole is a larvae of amphibians.

Fish therefore have observable scales while tadpoles have moist skin.

As tadpoles grow they loose their gills which grow into legs.

Behavior is observable.

We are at the centre of the observable universe, keyword being 'observable'.