Life on Earth is a diverse mix of organisms that are all inter-related and yet distinct. The tree of life below represents the relationships between all living things.
Figure 25. A phylogenetic tree of living things, based on RNA data and proposed by Carl Woese, showing the separation of bacteria, archaea, and eukaryotes. Trees constructed with other genes are generally similar, although they may place some early-branching groups very differently, thanks to long branch attraction. The exact relationships of the three domains are still being debated, as is the position of the root of the tree. It has also been suggested that due to lateral gene transfer, a tree may not be the best representation of the genetic relationships of all organisms. For instance some genetic evidence suggests that eukaryotes evolved from the union of some bacteria and archaea (one becoming an organelle and the other the main cell).
"Phylogenetic Tree of Life" by Eric Gaba, Wikimedia Commons is in the Public Domain
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