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In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization , from kingdoms to species , and individual organisms and molecules , such as DNA and proteins .
A tree of life, like this one from Charles Darwin's notebooks c. July 1837, implies a single common ancestor at its root (labelled "1"). A phylogenetic tree directly portrays the idea of evolution by descent from a single ancestor. [3] An early tree of life was sketched by Jean-Baptiste Lamarck in his Philosophie zoologique in 1809.
Megaevolution has been extensively debated because it has been seen as a possible objection to Charles Darwin's theory of gradual evolution by natural selection. [1] A list was prepared by John Maynard Smith and Eörs Szathmáry which they called The Major Transitions in Evolution. [2] [3] On the 1999 edition of the list they included:
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
Modern evidence suggests that early cellular evolution occurred in a biological realm radically distinct from modern biology. It is thought that in this ancient realm, the current genetic role of DNA was largely filled by RNA, and catalysis was also largely mediated by RNA (that is, by ribozyme counterparts of enzymes).
The traditional view is that developmental biology played little part in the modern synthesis, [45] but in his 1930 book Embryos and Ancestors, the evolutionary embryologist Gavin de Beer anticipated evolutionary developmental biology [46] by showing that evolution could occur by heterochrony, [47] such as in the retention of juvenile features ...
Eukaryogenesis, the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved symbiogenesis , in which an archaeon and a bacterium came together to create the first eukaryotic ...
Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship (shared descent), progenitor-descendant relationship (serial descent), and degree of evolutionary change.