Wonders of Life: Exploring the Most Extraordinary Phenomenon in the Universe (Wonders Series)

by Brian Cox

Cells are divided into two distinct types: eukaryotes and prokaryotes. Prokaryotic cells are the simpler of the two, containing far less cellular machinery and, crucially, lacking a nucleus. This is the structure of the simplest life forms on Earth – the bacteria and archaea. Prokaryotic organisms are almost always unicellular, and provide the clearest living example of how life must have looked and lived during the first 2 billion years of life on Earth. Eukaryotic cells, in comparison, are far more complex machines that emerged only around 2 billion years ago. These cells are the building blocks of human beings and every creature on Earth that we would regard as complex – from fungi to plants, from protists to animals. Compared to the simplicity of bacteria or archaea, the eukaryotic cell appears like a twenty-first-century factory, full of advanced structural technology, compared to an artisan’s workshop. As well as a nucleus containing all the cell’s chromosomal DNA, the inside of a eukaryotic cell is packed full of other functional units. The most striking for our story – a crystalised echo of the eukaryotes’ evolutionary past – are the mitochondria.