2020年1月30日 · Learn about the evolution of vertebrate animals, from tiny proto-fish 500 million years ago to the birds, mammals, and reptiles of today.

2025年3月14日 · With an environment devoid of oxygen and high in methane, for much of its history Earth would not have been a welcoming place for animals. The earliest life forms we know of were microscopic organisms (microbes) that left signals of their presence in rocks about 3.7 billion years old.

When we domesticated them, keeping animals as pest controllers, hunters, guardians, and livestock, civilization eventually flourished. In this list, we’ll look at some of the animals that made this possible. We’ll also look at individual animals notable for acts of great valor.

2009年7月14日 · The story of evolution spans over 3 billion years and shows how microscopic single-celled organisms transformed Earth and gave rise to complex organisms like animals

Animals appeared on Earth after a long period of evolution from single-celled organisms. The details of exactly when and how that happened are still largely unknown, although there is evidence that the Ediacaran period (about 630 to 540 million years ago) saw the evolution of a large number of relatively complex forms of life that probably ...

Earth has been home to over five billion different species of organisms. Of all of those living life forms, an estimated 99% of all species are now extinct. We, humans, are currently sharing the earth with about 12 million other species. So how did it end up this way, and who lived before us?

2025年3月21日 · Animals first appeared in the Ediacaran Period (about 635 million to 541 million years ago), soft-bodied forms that left traces of their bodies in shallow-water sediments. The best-known are coelenterates of various sorts, including some that were more irregular than any today, and there are several groups with unclear affinities .

Between 390 and 360 million years ago, the descendents of these organisms began to live in shallower waters, and eventually moved to land. As they did, they experienced natural selection that shaped many adaptations for a terrestrial way of life.

Over 600 million years ago, animals evolved from a unicellular or colonial organism whose cell(s) captured bacteria with a collar complex, a flagellum surrounded by a microvillar collar. Using principles from evolutionary cell biology, we reason ...

Life originated only once, in the sea, and for hundreds of millions of years the only animals on the planet were marine animals. Today there exist also terrestrial animals. At some point evolution had to take steps onto the land.