Two and a half billion years ago, the Archaean Eon ended and the Proterozoic Eon began. Trillions of prokaryote cells lived in Earth's oceans. Some of these cells could photosynthesize their energy [...]
A network of neurons One-celled creatures like bacteria don't have neurons, because they can communicate within themselves through the use of enzymes, but all multicellular animals do have neurons. The [...]
The yellow string is one of the arm nerves of a cat By around two billion years ago, some eukaryote cells were able to sense changes in their surroundings and [...]
A flatworm with eye-spots Eyespots came first Living creatures have been able to tell if it's light out or not for about two billion years. That's when some eukaryote cells evolved to [...]
This is a mouse brain When did the first brains evolve? Flatworms were the first animals to evolve anything like a brain, but it's really just a thickened part of [...]
A black woman shows off her muscles One-celled creatures don't have any muscles; the ones that can move themselves use flagellae instead. Even after living creatures evolved that had a [...]
A flatworm When did flatworms evolve? The first flatworms, or platyhelminthes, probably evolved from something like a hydra about 550 million years ago. What's a hydra? Proterozoic Eon All our [...]
