what is this aforesaid period?
It was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon.
Cambrian
The Cambrian Period ( ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. 
in which evolutionary force does competition play the biggest role UNANSWERABLE what is apex predator? An apex predator, also known as an alpha predator or top predator, is a predator at the top of a food chain, without natural predators. how is it conserved? By reintroducing them to nature . what effect does it have on community? Apex predators affect prey species' population dynamics and populations of other predators, both in aquatic and in terrestrial ecosystems. what is its history in evolution? Apex predators are thought to have existed since at least the Cambrian period, around 500 million years ago.
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Cambrian [SEP] Introduction
The Cambrian Period ( ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established (as “Cambrian series”) by Adam Sedgwick, who named it after Cambria, the Latin name of Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells.