Major Transitions

Many major evolutionary transitions evolve a transition from a "group of organism" to a "group as organism", for example the transition from prokaryotes to eukaryotes, from unicellular eukaryotes (green or red algae) to multicellular eukaryotes (animals, plants, fungi), and from human to societies. Eukaryotes are organisms whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, within which the genetic material is carried. Simple eukaryotic organisms are for instance red and green algae. Examples for prokaryotes are bacteria. Eukaryotes evolved from prokaryotes more than 2 billion years ago. Eukaryotic cells probably originated as a group or community of prokaryotes.