Tetrapod#From water to land

As shore is called the gradual adaptation of aquatic life to a terrestrial lifestyle, so the process of land colonization by previously adjusted exclusively to life in aquatic organisms. This process has repeated itself and occurred independently of each other, so for example, in unicellular organisms, fungi, plants, invertebrates and vertebrates.

Plant

Through fossil evidence relatively well documented is the shore of plants, most researchers today to before 480-460 million years ago - is dated - the early Ordovician. The advent of land plants escaped the atmosphere of carbon dioxide, a process that was enhanced by plants caused by weathering processes of the soil. An Ordovician detectable, noticeable cooling of the climate was interpreted in 2012 by a research group as a result of the altered carbon cycle after the land settlement.

As one of the earliest, but already well-adapted to life on land land plants shall Rhynia gwynne - vaughanii that lived in the Devonian about 400 million years ago.

Gregory J. Retallack from the University of Oregon, an expert on paleosols, argued in 2013 in Nature, at least some species of the 600 million year old Ediacaran fauna were parts of an early land flora, with a growth form, which was comparable to that of the extant lichens or with colonies of microorganisms.

A team of authors of the Pennsylvania State University, according could green algae as well as sac fungi socialized cyanobacteria ( ie earliest preforms today lichens) have been much earlier colonized the country: With the help of molecular biological estimates ( "molecular clock " ) calculated them for the land plants, a first settlement before 700 million years ( Cryogenium ) and green algae and fungi a billion years ago ( Stenium / Tonium ). For this basis calculated from protein sequences estimates, however, there has hardly fossil evidence; published in 2011, however, at least evidence of eukaryotic organisms that at that time " in fresh water or on the surface " lived.

Vertebrates

Well supported by fossils, however, is the shore of vertebrates ( tetrapods ) during the Devonian, so the evolutionary transition from freshwater fish living bone to the preforms of the present-day amphibians. Here, the shape change can ( phylogeny ), shall, inter alia, of animals similar Gogonasus on species that resembled Eusthenopteron, Panderichthys, Elginerpeton, Metaxygnathus, Tiktaalik and Ventastega to the early tetrapods Acanthostega and Ichthyostega based on well-preserved finds to be very plausible. But is still unclear to what section of the Devonian this country run was carried out; the oldest fossils are in fact around 18 million years younger than the oldest one tetrapods living beings attributed fossil footprints have been dated at 397 million years. As an era of shore of tetrapods the time was named before 416-359 million years ago in 2010 in Nature. Maybe the land settlement was by vertebrates the indirect result of a mass extinction 360 million years: The surviving species colonized new habitats, including the mainland.

What changes in the genome, for example, the " conversion " of fins enabled in feet, is largely unknown; particular Hoxd13 - - but genes from the group of 5'Hoxd group seem to have been involved. The land-living tetrapods had at first - millions of years - still a "fishy " pine, which were likely to tear flesh; only 320 million years ago the shape of the jaw has been increasingly " reptilian ". It is assumed that only the mobility of the ribs and the surrounding respiratory muscles was so far developed then that they could contribute to suck the breath considerably, which in turn meant that muscles and bones relieved in the jaw by the air suction and stronger than could previously be used for chewing.

Arthropod

Various sub- tribes of arthropods have probably several times the " step " completed evolutionary parallel from water to land, both marine as of süßwasserbewohnenden forms (see also analogous developments ). This may be the reason damp bank have shown a suitable transition field for digging, burrowing forms.