Timeline of evolution (Wiki)
Evolution and overview of classical transmitters (PubMed)
"The earth is probably about 4-5 billion years old with the oldest rocks being around 3-9 billion years. However these are too metamorphosed by subsequent heat and pressure to allow the preservation of fossil material (Gould, 1994). The oldest rocks which could retain fossil material are from Africa and Australia and are around 3-5 billion years old.
These contain prokaryotic cells, for example, bacteria and cyanophytes which indicates that life evolved relatively quickly. The first eukaryotic cells probably appeared around 2 billion years ago with the differentiation between animals and plants occurring about 1*2 billion years ago. Yeasts and molds are estimated to have appeared between 900 million and 1 billion years ago with primitive multicellular helminth-like organisms appearing around 800 million years ago (Peroutka, 1994).
The divergence of vertebrates from the other animal groups would appear to have occurred around 600 million years ago at the end of the precambrian period. The first vertebrate fossils appear around 500 million years ago (Colbert & Morales, 1991). ... Mammals arrived on the scene around 300 million years ago from a primitive stem reptile while birds diverged from reptiles after the divergence of mammals but within the same approximate time scale."
Origin and early evolution of the vertebrates: new insights from advances in molecular biology, anatomy, and palaeontology.
"Recent advances in molecular biology and microanatomy have supported homologies of body parts between vertebrates and extant invertebrate chordates, thus providing insights into the body plan of the proximate ancestor of the vertebrates. For example, this ancestor probably had a relatively complex brain and a precursor of definitive neural crest. Additional insights into early vertebrate evolution have come from recent discoveries of Lower Cambrian soft body fossils of Haikouichthys and Myllokunmingia (almost certainly vertebrates, possibly related to modern lampreys) and Yunnanozoon and Haikouella (evidently stem-group vertebrates). The earliest vertebrates had an unequivocally marine origin, probably evolved mineralised pharyngeal denticles before the dermal skeleton, and evidently utilised elastic recoil of the visceral arch skeleton for suction feeding. Moreover, the new data emphasise that the advent of definitive neural crest was supremely important for the evolutionary origin of the vertebrates."
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Origins of anteroposterior patterning and Hox gene regulation during chordate evolution.
Free PMC Article
Evolution of the brain developmental plan: Insights from agnathans.
"In vertebrate evolution, the brain exhibits both conserved and unique morphological features in each animal group. Thus, the molecular program of nervous system development is expected to have experienced various changes through evolution. In this review, we discuss recent data from the agnathan lamprey (jawless vertebrate) together with available information from amphioxus and speculate the sequence of changes during chordate evolution that have been brought into the brain developmental plan to yield the current variety of the gnathostome (jawed vertebrate) brains."
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Note: This is a very good article with unusually good diagrams.
Evolution of the animals: a Linnean tercentenary celebration (Goog)
Table of Contents - The session titles are active links.
This webpage was a reference for the Wikipedia page on 'Xenoturbella'.
Evidence of 3.5-billion-year-old bacterial ecosystems found in Australia