Final answer:
The Neo-Proterozoic Era ended and the Palaeozoic Era began around 541 million years ago, marked by the Cambrian explosion and ending with the Permian extinction.
Step-by-step explanation:
The Neo-proterozoic Era ended and the Paleozoic Era began approximately 541 million years ago. This transition marks the conclusion of the Neoproterozoic Era and the onset of the Cambrian Period, the first period within the Paleozoic Era, which lasted until about 485 million years ago. The Palaeozoic Era, often referred to as the age of "old life," spanned from 541 to 251.902 million years ago, ultimately concluding with the Permian extinction. The start of the Palaeozoic was characterized by the Cambrian explosion, a significant diversification of life on Earth.