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 [...]
Archaean Eon: A volcano erupts out of the water The beginning of the Archaean Eon After the end of the Hadean Eon is the beginning of the Archaean Eon. That's about [...]
RNA molecule: A single strand of RNA, seen under an electron microscope The RNA molecule was probably one of the earliest steps towards life on Earth. RNA is short for [...]
A cell dividing into two cells The first reproduction One of the main ways we define whether something is alive is whether it can reproduce - if it can make a new [...]
A prokaryote (seen through a microscope) What does "prokaryote" mean? The simplest living cells are called prokaryotes, which is Greek for "before the nucleus" - these are cells that were [...]
Chloroplasts (seen through a microscope) Photosynthesis is the way some cells on Earth pull in light from the sun and use it to make energy to repair and reproduce themselves. [...]
An onion skin cell (seen through a microscope) You can see the nucleus inside each cell The earliest cells, and all prokaryote cells, don't have a nucleus. Inside these simple [...]
A mitochondrion (seen through a microscope) When did mitochondria evolve? About two billion years ago, in the Proterozoic, there were only prokaryotic cells on Earth. Mitochondria probably started out as [...]
One cell of a plant (magnified 22,500 times) Thanks to Ohio State University A cell is the smallest living thing (unless you count viruses), and all bigger living things are [...]
Eukaryotes (seen through a microscope) are full of chloroplasts When did eukaryotes evolve? Around two billion years ago, when all cells still lived in the ocean, a few of the [...]
