Question

why is the late Cambrian thought of as the period of the greatest evolutionary change in life forms on earth's history?

Answer 1

The late Cambrian is known for the Cambrian explosion, an event that saw rapid diversification of animal life and the emergence of most modern animal phyla.

Step-by-step explanation:

The late Cambrian is often considered the period of the greatest evolutionary change in life forms on Earth's history due to the event known as the Cambrian explosion. This was a time, roughly 542-488 million years ago, marked by the rapid diversification of animals and the emergence of most animal phyla we see today. Predatory creatures like Anomalocaris, arthropods, echinoderms, mollusks, worms, and early chordates appeared, exhibiting complex body forms that had not been seen before.

Several theories have been posed to explain this rapid evolution. These include environmental changes like rising atmospheric oxygen, increases in oceanic calcium concentrations and the availability of new ecological niches due to extensive continental shelves. Some scientists also point to ecological relationships and genetic factors such as the evolution of Hox control genes, which provided additional possibilities in animal development.

Despite the massive extinction events that followed, the vast number of phyla that appeared during the Cambrian period has persisted to the present day. This astonishing fact highlights the Cambrian's extraordinary impact on the course of life's evolution on our planet.

Answer 2

The Cambrian Period marks an important point in the history of life on Earth; it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the "Cambrian Explosion," because of the relatively short time over which this diversity of forms appears.