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Proterozoic Eon – eukaryotes to worms

By |2018-04-21T11:56:39+00:00June 24th, 2017|Biology, Geology|

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 from sunlight, water, and carbon dioxide. These photosynthesizing cells pooped out a lot of oxygen. By about 2.3 billion years ago, the iron [...]

What is RNA? Cell biology and evolution

By |2018-04-16T00:39:56+00:00May 29th, 2017|Biology|

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 "ribonucleic acid". That's a very long, complicated molecule made out of amino acids linked together. The amino acids are made out of atoms of [...]

What is a prokaryote – Cell biology

By |2018-09-11T05:51:18+00:00May 29th, 2017|Biology|

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 so simple that they didn't have a nucleus. When did the first prokaryotes evolve? The first prokaryotes probably evolved from even simpler cells [...]

What is photosynthesis? Plant Biology

By |2018-04-16T00:37:36+00:00May 29th, 2017|Biology|

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. The first cells could not photosynthesize (foe-toe-SIN-the-size). They got food by breaking apart hydrocarbon molecules. But a little more than three billion years ago, [...]

What is a nucleus – Parts of a cell – Biology

By |2017-05-29T00:35:47+00:00May 29th, 2017|Biology|

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 cells, the DNA molecules just float around in the cytoplasm. This is a nice simple arrangement, but it's risky - the DNA often [...]

What are mitochondria? Parts of a cell – Biology

By |2017-05-29T00:26:07+00:00May 29th, 2017|Biology|

A mitochondrion (seen through a microscope) About two billion years ago, in the Proterozoic, there were only prokaryotic cells on Earth. Mitochondria probably started out as independent cells that were especially good at digesting food. These cells were extra good at digesting because they had evolved to have two membranes. The inside membrane, [...]

How did cells evolve? Cell biology and evolution

By |2018-04-16T00:35:42+00:00May 28th, 2017|Biology|

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 made of cells. Both plants and animals are made of cells. We don't know yet whether there are cells on any other planet [...]

What are eukaryotes? Cell biology

By |2017-05-28T22:37:27+00:00May 28th, 2017|Biology|

A eukaryote cell (seen through a microscope) full of chloroplasts Around two billion years ago, when all cells still lived in the ocean, a few of the earliest cells, or prokaryotes, evolved into more complicated cells called eukaryotes. They seem to have done this by enclosing several different kinds of prokaryotes inside another [...]