Devonian period

Estimates like these indicate that hemoglobins arc very old and that 11 may he possible 10 tind relatives of vertebrate hemoglobins in in erlebrute animals. They also suggest ihal the gene duplication believed 10 lie responsible fix the divergence ot die or- and /(-chains took place in ihe Devonian period at the time of the appearance ol early amphibians and die dominance of (is.lt. 

Fig. 13.3. This figure provides another example of the incongruity of fossil records and molecular genealogy. Using humans as a standard, all mammals that purportedly are closely related have relaxins that are not more closely related to human relaxin than to that of skates and sharks. Since skates and sharks have been around in the Devonian period 380,000,000 years ago, the structural dissimilarity of the various relaxin molecules would suggest that the branching point between humans, horses, rats, etc., as well as sharks would have occurred 380,000,000 years ago. Conversely, the mammalian explosion is placed at about 60,000,000 years, which would force all the molecular genealogy lines to converge at a point 60,000,000 years ago, giving us a 300,000,000 years uncertainty. This difference is not trivial, it represents 3/3 of the total time of macro-organismic development.

There are only a few fossils of liverworts and mosses and there are no fossils of hornworts. This is because the soft tissue of these bryophytes does not fossilize well. The oldest known liverwort fossil is from the late Devonian period, about 350 million years ago. Most botanists believe that they originated long before this. 

The 50 million years of the Devonian Period provided sufficient time for over 11,000 feet of sedimentary rocks to accumulate in the Appalachian Basin this accumulation was controlled by pulses of tectonic uplift to the east. A similar control of a northwestern source area by intermittent tectonic movement is suggested as a source for the upper wedges (B/C) in the Michigan and Illinois Basins. The lower black shales (A) of regional type represent quiescent periods of slow deposition followed by relatively more rapid sedimentation occurring in response to uplift and erosion of source areas and to depositional restrictions caused by rising arches. The total thickness of Devonian shales in either the Michigan or Illinois Basin is less than 1000 feet, so that the sediment volume involved in these two basins is far less than in the Appalachian Basin. Thus there was ample time for... 

Fossil Record. The fossil record contains evidence that white-rot fungi have been present since the upper Devonian period (23). Fungi with hyphal characteristics of basidiomycetes were found associated with a decay of Callixylon wood that was similar to modern white rot. Cell wall erosion and coalescing of erosion troughs indicated it was the type of white rot that simultaneously degrades all cell wall components. Specimens of Vertebraria from the Permian also have been observed with a white rot (24). The decay was characterized by cell walls that were progressively reduced in thickness, and eventually the entire cell wall was removed. 

Clay deposits of the Devonian Period are used for brickmaking in South Devon and Cornwall and around Cardiff and Newport. 

Silurian A geological period of the Palaeozoic era following the Ordovician period and extending until the beginning of the Devonian period. It began about 444 million years ago and lasted for about 28 million years. 

U ). Compounds of are deposited with the sediment because they are far less soluble than compounds of UOf. The uranium in ground water is released into solution by chemical weathering of plutonic and volcanic igneous rocks. The fixation of tetravalent uranium in sedimentary rocks of the Beacon Supergroup became possible because land-based plants that evolved during the Devonian Period provided organic matter that was buried with the sediment. 

It should be noted, however, that deposits of vegetable matter are not limited to any particular era or period, but while these deposits occur even in pre-Cambrian rocks, the plants (i.e., terrestrial plants) that were eventually to become coal were not sufficiently abundant until the Devonian Period and it appears that such deposits really became significant during the Carboniferous Period. 

Coal is the compacted and preserved ranains of plant matter and when plant life containing cellulose-rich stems and leaves is highly abundant and special conditions exist (usually anaerobic conditions)—the plant matter does not totally decompose and is preserved in fossilized form. These types of plants had evolved by the Devonian Period and many coal deposits in Europe and North America date from the Carboniferous Periods of the Paleozoic when these areas were covered with forests dominated by large ferns and scale trees. 

Coals are formed in swamps under warm climatic conditions that promote rapid vegetative growth. Coal deposits are generally associated with mountain-building events and deltaic environments. Coals can be traced to the Devonian period, when woody plants first evolved, about 370 million years before the present. 

Atmospheric sciences is the study of various aspects of the nature of the atmosphere, including its origin, layered structure, density, and temperature variation with height natural variations and alterations associated with anthropogenic impacts and how it is similar to or different from other atmospheres within the solar system. The present-day atmosphere is in aU likelihood quite dissimilar from the original atmosphere. The form and composition of the present-day atmosphere is believed to have developed about 400 million years ago in the late Devonian period of the Paleozoic era, when plant life developed on land. This vegetative cover allowed plants to take in carbon dioxide and release oxygen as part of the photosynthesis process. 

The Devonian Period of the Paleozoic Era lasted from 417 million years ago to 354 million years ago. It is known as the Age of Fishes and came to an end in a dramatic mass extinction. 

Pteridophytes. Evolution of the biochemical pathway to the lignins proper apparently first occurred with the appearance of the pteridophytes, the earliest remains of which to date come from the Devonian period (27). In extant plants, lignins are seemingly present in the ferns (Filicopsida), clubmosses (Lycopsida), horsetails (Equisetopsida), and the Psilotopsida [see... 

Dming the Devonian period two supercontinents, Gondwana and Eurasia, existed. They were moving close together (to collide during the... 

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