Reference no: EM133971072

Question

Life is divided into three domains: Domain Bacteria, Domain Archaea, and Domain Eukarya. Today we will focus on the organisms that make-up those first two domains - the prokaryotes. Prokaryotic cells are the smallest and simplest form of life. Their cells have no internal membranes, so no nucleus, no endoplasmic reticulum, no mitochondria or chloroplast. However, this doesn't mean they are unimportant! Life on Earth began with prokaryotic organisms approximately 3.6 billion years ago (roughly 1 billion years after the Earth was formed!). Eukaryotic cells would not appear for another 1.6 billion years, so for a long time this planet was a bacteria world (and in many ways, it still is!). Fossilized prokaryotes, called stromatolites, have been collected from around the world. Stromatolites formed billions of years ago when aquatic bacteria attached to solid surfaces like sediment grains or each other. These attached cells sank to the bottom of the aquatic environment and formed a microbial mat, or biofilm. These mats were covered with layers of silt (fine mud and sand), then another layer of bacteria, then more silt, and so on. The earliest bacteria in the fossil record are the cyanobacteria, which are autotrophic (they can perform photosynthesis and.