Shore leave (biology)

from Wikipedia, the free encyclopedia
Artist's impression of Tiktaalik roseae

As ashore is called the gradual adaptation of aquatic creatures to terrestrial life, so the process of land colonization by previously adjusted solely to life in aquatic organisms. This happened repeatedly and independently of one another in different groups of organisms, for example in protozoa , fungi , plants , annelid worms , arthropods , snails and vertebrates .

Microorganisms

The oldest traces of life on land probably come from microorganisms that lived 3.48 billion years ago in the hot springs of what is now known as the Dresser Formation in Western Australia .

The next younger traces of life of suspected microorganisms from the paleo soil of a former river plain in today's South Africa are 3.2 billion years old . These are tiny grains of the mineral pyrite , in which the ratio of the sulfur isotopes 34 S and 32 S in particular has been interpreted as an indication of the influence of microorganisms.

plants

Reconstruction of Rhynia

The shore leave of the plants is relatively well documented by fossil evidence , which most researchers today date to the time before 480 to 460 million years ago - the early Ordovician - and partly to early species of ornamental algae from the group of Streptophyta , partly to the candelabrum algae (Charophyceae or Charales).

The emergence of land plants drew carbon dioxide from the atmosphere, a process that was exacerbated by the weathering of the soil caused by plants. A noticeable cooling of the climate, detectable in the Ordovician, was interpreted in 2012 by a research group as a consequence of an influence on the carbon cycle as a result of land colonization by early plants. Rhynia gwynne-vaughanii , which lived in the Devonian around 400 million years ago, is considered to be one of the earliest land plants, albeit well adapted to rural life .

Gregory J. Retallack of the University of Oregon , an expert on paleo soils , argued in 2013 that at least some species of the approximately 600 million year old Ediacaran fauna were representatives of an early terrestrial flora , with a growth form that was comparable to that Lichen living today or with colonies of microorganisms .

According to a team of authors from Pennsylvania State University , green algae and cyanobacteria (i.e. the earliest preforms of lichens) associated with sac fungi could have colonized the country much earlier: With the help of the “ molecular clock ” they calculated that land plants ( cryogenium ) were for the first time 700 million years ago could have colonized continental areas, green algae and fungi even a billion years ago ( stenium / tonium ). So far, however, there is hardly any fossil evidence for this data, which was determined using protein sequences. In 2011, however, at least indications of eukaryotic organisms that lived “in fresh water or on the earth's surface” were published in 2011 .

In 2018, a group of researchers led by Mark Puttick from the University of Bristol published a study suggesting the existence of moss-like plants on land around 515 million years ago (in the Middle Cambrian ). The study is based primarily on analyzes of the molecular clock, but also on fossils and indications of relationships between the groups of plants.

arthropod

Different sub-tribes of the arthropods have probably made several parallel evolutionary steps from water to land, both from marine and freshwater forms (see also analogous developments ). The damp bank ground may have represented a suitable transition area for digging and burrowing forms. For the insects , based on DNA analyzes (“ molecular clock ”), it was calculated that their ancestors passed from aquatic to land-settling ways of life around 480 million years ago and that the air also opened up as a habitat a little more than 400 million years ago. The 2.5 centimeter long fossil Kampecaris obanensis from the Silurian Mountains in Scotland , which resembles a millipede , was determined to be 425 million years old.

Vertebrates

Possible changes in shape when going ashore (from bottom to top):
Eusthenopteron , Panderichthys , Tiktaalik , Acanthostega , Ichthyostega , Pederpes
Simplistic animation to interpret fossil frühmitteldevonischer traces in coastal sedimentary rocks as the oldest (395  mya ) known vertebrate track

The shore excursion of vertebrates during the late Devonian , i.e. the evolutionary transition from freshwater bony fish to the early terrestrial vertebrates , is well secured by fossils . Here the change in shape in the course of the phylogenesis of these so-called parent tetrapods (also called "fish apods"), starting from representatives such as Gogonasus via species that resembled Eusthenopteron , Panderichthys , Elginerpeton , Metaxygnathus , Tiktaalik and Ventastega , to the earliest "real" four-legged forms, such as Acanthostega and Ichthyostega , can be traced relatively completely on the basis of well-preserved finds. So far it is unclear in which section of the Devonian this landfall took place. The oldest fossils are around 18 million years younger ( frasnium ) than the oldest fossil footsteps ascribed to a tetrapod living being , which were dated to an age of 397 million years ( emsium ). In connection with the latter discovery, the period of landfall of the vertebrates was estimated to be from 416 to 359 million years ago.

According to a study from 2016, there are currently 130 species of fish from 33 families , whose individuals are temporarily on land. From this it was concluded that the shore leave could also have occurred several times in the era of the so-called parent tetrapods.

It is largely unclear what changes in the genetic material made it possible, for example, to "convert" fins into feet. However, genes from the group of the 5'Hoxd group - especially Hoxd13 - seem to have been involved. While the postcranial skeleton u. a. With the loss of the unpaired fins, the change of the paired fins to legs and the detachment of the skull from the shoulder girdle, accompanied by the reduction of the gill cover, the lower jaw of the early tetrapods remained "fish-like" for many millions of years, and Form and function hardly varied between the different species. Only about 320 million years ago, with the appearance of the first amniotes ("reptiles") and amniote-like tetrapods, did the variability in the form and function of the lower jaw increase. This is associated with the acquisition of herbivory in these “higher” tetrapod groups. The reason for this delayed development is assumed that it was not until the amniote-like tetrapods and the early amniotes that the rib cage and the respiratory muscles attached to it formed a functional unit, with the help of which the lungs could be expanded and compressed like a bellows ( costal ventilation ), while the more original tetrapods pressed the air into the lungs with the help of the muscles in the floor of the mouth ( buccal pumping ), as the representatives of the modern amphibians still do today . The transition to costal ventilation resulted in the lower jaw being relieved in its special function as a base for the respiratory muscles in the floor of the mouth, which in turn allowed the development of a greater variety of shapes and thus also opened up opportunities for greater food specialization.

In the course of their individual development during the metamorphosis of the larva into the frog or tailed amphibian, the modern amphibians follow the landfall of the tetrapods within a few days to weeks, an example of Ernst Haeckel's basic biogenetic rule .

The shore leave of the vertebrates could have started due to environmental changes in combination with phenotypic plasticity . What is meant is the variability of the phenotype depending on environmental influences: two individuals of the same species who grow up under different environmental conditions can develop slightly different physical characteristics. To this end, Canadian evolutionary researchers undertook an experiment with pike-pike living today in order to recreate the processes of that time. Flösselhechte live in the fresh waters of tropical Africa and are considered to be the “most primitive” of recent ray fins. This means that they can serve as a modern analogue to the fish-like flesh-flippers from which the first terrestrial vertebrates emerged in the Devonian . In an eight-month experiment, they observed how juvenile Senegalese pike ( Polypterus senegalus ) developed physically if they were completely denied the opportunity to go into the water. As a result of the lack of buoyancy, both the muscles and the bone structure, especially the pectoral fins and the shoulder girdle, changed. This happened in a similar way as it can be observed in the fossil record of Devonian fish-like meat-pods (e.g. Eusthenopteron ), "fish apods" (e.g. Tiktaalik ) and the earliest four-legged representatives (e.g. Ichthyostega ). The test individuals were also able to “walk” significantly better on dry land than the individuals in the control group, which was mostly kept in the water . Such initially only phenotypic adaptations could also have occurred 400 million years ago in the fish-like precursors of the tetrapods and were only subsequently fixed in the affected population by genetic mutations via selection . The evolutionary sequence would therefore not be: random genetic mutation → natural selection → adaptation in the population, but the other way around: change in environmental conditions → permanent, not yet genetically hereditary phenotypic adaptation → genetic fixation ( genetic assimilation ) of phenotypic adaptation through random mutations. However, this scenario contradicts the previous knowledge about the evolution of the ancestral tetrapods, according to which legs and toes should have arisen before the transition to a terrestrial way of life.

Another example of a rayfloss that has conquered somewhat dry terrain is the mudskipper . In contrast to the Devonian tribal tetrapods and the pike, the mudskipper is a "shore leave" in the marginal marine environment.

See also

literature

Web links

Individual evidence

  1. ↑ Tara Djokic et al .: Earliest signs of life on land preserved in approx. 3.5 Ga hot spring deposits. In: Nature Communications. Volume 8, Article No. 15263, 2017, doi: 10.1038 / ncomms15263
    Oldest evidence of life on land found in 3.48-billion-year-old Australian rocks. On: eurekalert.org from May 9, 2017
  2. ↑ Sami Nabhan, Michael Wiedenbeck, Ralf Milke and Christoph Heubeck: Biogenic overgrowth on detrital pyrite in about 3.2 Ga Archean paleosols. In: Geology. Volume 44, No. 9, 2016, p. 763 ff., Doi: 10.1130 / G38090.1
    Life on land is 300 million years older than expected. On: idw-online.de. from November 7, 2016
  3. ↑ Jan de Vries, Bruce A. Curtis, Sven B. Gould and John M. Archibald: Embryophyte stress signaling evolved in the algal progenitors of land plants. In: PNAS . Volume 115, No. 15, E3471 – E3480, 2018, doi: 10.1073 / pnas.1719230115
  4. ↑ Tomoaki Nishiyama, Hidetoshi Sakayama et al .: The Chara Genome: Secondary Complexity and Implications for Plant Terrestrialization. In: Cell . Volume 174, No. 2, 2018, pp. 448–464.e24, doi: 10.1016 / j.cell.2018.06.033
    Solid cell wall prepared for shore leave     . On: idw-online.de from July 12, 2018
  5. ↑ Timothy M. Lenton, Michael Crouch Martin Johnson, Nuno Pires, Liam Dolan: First plants cooled the Ordovician. In: Nature Geoscience . Volume 5, 2012, pp. 86-89, doi: 10.1038 / ngeo1390 .
  6. ^ L. Paul Knauth: Not all at sea. In: Shuhai Xiao, L. Paul Knauth: Forum Palaeontology: Fossils come in to land. In: Nature . Volume 493, No. 7430, 2013, pp. 28-29, doi: 10.1038 / nature11765 .
  7. ^ Gregory J. Retallack: Ediacaran life on land. In: Nature. Volume 493, No. 7430, 2013, pp. 89-92, doi: 10.1038 / nature11777 .
  8. ^ Daniel S. Heckman, David M. Geiser, Brooke R. Eidell, Rebecca L. Stauffer, Natalie L. Kardos, S. Blair Hedges: Molecular Evidence of the Early Colonization of Land by Fungi and Plants. In: Science . Volume 293, No. 5532, 2001, pp. 1129-1133, doi: 10.1126 / science.1061457 .
  9. ^ Paul K. Strother, Leila Battison, Martin D. Brasier, Charles H. Wellman: Earth's earliest non-marine eukaryotes. In: Nature. Volume 473, No. 7348, 2011, pp. 505-509, doi: 10.1038 / nature09943 .
  10. ↑ Jennifer L. Morris et al .: The timescale of early land plant evolution. In: PNAS. Volume 115, No. 10, 2018, E2274 – E2283, doi: 10.1073 / pnas.1719588115 Martin Vieweg: Shore of the plants predated. In: Wissenschaft.de datum = 2018-02-19. Retrieved March 25, 2018 .
  11. ^ MG Villani et al .: Adaptive strategies of edaphic arthropods. In: Annual Review of Entomology. Volume 44, 1999, pp. 233-256 doi: 10.1146 / annurev.ento.44.1.233 .
  12. ↑ Bernhard Misof et al .: Phylogenomics Resolves the timing and pattern of insect evolution. In: Science. Volume 346, No. 6210, 2014, pp. 763–767, doi: 10.1126 / science.1257570
    Spectacular success: researchers clarify the evolution of insects using DNA analyzes. On: idw-online from November 6, 2014.
  13. ↑ ME Brookfield, EJ Catlos and SE Suarez: myriapod divergence times differentiate between molecular clock and fossil evidence: U / Pb zircon ages of the earliest fossil millipede-bearing sediments and Their significance. In: Historical Biology. Online publication from May 15, 2020, doi: 10.1080 / 08912963.2020.1762593 .
    Scientists find oldest fossil of a land animal. On: cbc.ca from June 1, 2020.
  14. ↑ a b Grzegorz Niedźwiedzki et al. : Tetrapod trackways from the early Middle Devonian period of Poland. In: Nature , Volume 463, 2010, pp. 43-48, doi : 10.1038 / nature08623 .
  15. ↑ Jennifer Clack: Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods. Second edition. Indiana University Press, Bloomington (IN) 2012, ISBN 978-0-253-35675-8 .
  16. ^ Robert Carroll: The Rise of Amphibians: 365 Million Years of Evolution. Johns Hopkins University Press, Baltimore (MD) 2009, ISBN 978-0-801-89140-3 .
  17. ↑ Michael J. Benton: Paleontology of the vertebrates. Translation of the 3rd English edition by Hans-Ulrich Pfretzschner. Publishing house Dr. Friedrich Pfeil, Munich 2007, ISBN 978-3-89937-072-0 , p. 88 ff.
  18. ^ Donald Prothero: What missing link? Reports of huge gaps in the fossil record have been greatly exaggerated. In: New Scientist . No. 2645, pp. 35-41, doi: 10.1016 / S0262-4079 (08) 60548-5 (alternative full text access : donaldprothero.com ).
  19. ^ Philippe Janvier, Gaël Clément: Palaeontology: Muddy tetrapod origins. In: Nature. Volume 463, No. 7277, 2010, pp. 40-41, doi: 10.1038 / 463040a .
  20. ↑ Terry J. Ord and Georgina M. Cooke: Repeated evolution of amphibious behavior in fish and its implications for the colonization of novel environments. In: evolution. Volume 70, No. 8, 2016, pp. 1747–1759, doi: 10.1111 / evo.12971
    Fish may have evolved to live on land more than 30 times. On: sciencemag.org from June 16, 2016
  21. ^ Renata Freitas Carlos Gómez-Marín, Jonathan Mark Wilson, Fernando Casares, José Luis Gómez-Skarmeta: Hoxd13 Contribution to the Evolution of Vertebrate Appendages. In: Developmental Cell. Volume 23, No. 6, 2012, pp. 1219-1229, doi: 10.1016 / j.devcel.2012.10.015 ; see also From Fish to Human: Research Reveals How Fins Became Legs. Article on Cell Press ScienceDaily on December 10, 2012.
  22. ^ A b Philip SL Anderson, Matt Friedman, Marcello Ruta: Late to the Table: Diversification of Tetrapod Mandibular Biomechanics Lagged Behind the Evolution of Terrestriality. In: Integrative and Comparative Biology. Volume 53, No. 2, 2013, pp. 197-208, doi: 10.1093 / icb / ict006 .
  23. ↑ Christine M. Janis, Julia C. Keller: Modes of ventilation in early tetrapods: Costal aspiration as a key feature of amniotes. In: Acta Palaeontologica Polonica. Volume 46, No. 2, 2001, pp. 137-170 (online).
  24. ^ Emily M. Standen, Trina Y. Du, Hans CE Larsson: Developmental plasticity and the origin of tetrapods. In: Nature. Vol. 513, 2014, pp. 54-58, doi: 10.1038 / nature13708 ; see also: Noah Baker: How fish can learn to walk - Land-raised bichirs provide insight into evolutionary pressures facing first vertebrates to live on land. Nature Video of August 27, 2014 (commentary in English).
  25. ^ Stephanie E. Pierce, Jennifer A. Clack, John R. Hutchinson: Three-dimensional limb joint mobility in the early tetrapod Ichthyostega. In: Nature. Vol. 486, No. 7404, 2012, pp. 523-526, doi: 10.1038 / nature11124 .