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 [...]
Human sperm cells with flagella (under a microscope): Eukaryote flagella Not the old kind of flagella About two billion years ago, the first eukaryote cells evolved from the earlier prokaryote [...]
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 [...]
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 [...]
Lysosomes (under an electron microscope) When did lysosomes evolve? Prokaryote cells don't have lysosomes, so the first ones probably evolved about the same time as the other pieces of eukaryote [...]
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 [...]
Cell waste: A cell with a vacuole Cell waste and vacuoles Soon after eukaryote cells began to make vacuoles to help them catch their food and store it, about 600 [...]
