VertZooNotesDeuce - Vertebrate Zoology Notes Part 2 The...

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Vertebrate Zoology Notes Part 2 The Span of Time So Far (in regards to vertebrates) Have their start with the first tetrapods during the mid-Devonian. During this time the continents were drifting towards each other but had not formed Pangaea. Plant life at this time limited to wet patches that were dominated by a single species of very primitive plant. No insects on the land yet, only arachnids such as spiders, scorpions and pseudoscorpions feasting on myriapods. No terrestrial vertebrates as of this point. Late Devonian sees the rise of the first terrestrial vertebrate amongst predominantly spore bearing plants (ferns). Carboniferous is the time in which the modern structure of plants becomes dominant and conifers dominate. Terrestrial vertebrates abundant and include the arachnids, myriapods and now the insects. Tetrapods limited to dominant, aquatic forms. Permian was the time of Pangaea, the super continent that covered 36% of earth’s surface. Amniotes have become better developed for terrestrial environments and the ecosystems of earth at this time are functionally modern, just with a lack of angiosperms. Origin of Tetrapods Occurs in the mid to late Devonian, and terrestrial life may have conferred several advantages during this time. The Devonian was a time of seasonal drought and being able to survive outside or move between available bodies of water made an organism more fit. Could also be that there were less predators and competition on land, and as juveniles and lobe finned fish dwelt in the weedy area at the edge of the pond, where the lobes allowed them to move more effectively through such an environment, the movement to land would be advantageous. The problems with moving onto land are many. The organism must now develop a skeletal structure and limb placement that will allow it to support its own weight, function water used to play. While there is more oxygen in the atmosphere, the gill is completely useless in trying to draw it out. The process of desiccation must be overcome and maintaining body temperature becomes much more difficult. Finally, the sensor systems have to adapt to perceiving in a new medium. Major Groups and Characteristics They arose during the late Paleozoic, in the carboniferous, a time known as the age of amphibians. Today, there are roughly 4550 extant species, all identified by having moist, permeable skin lacking scales and no claws being present. Adult forms are carnivorous while larval forms may not be. Order Caudata (Urodela) These are the salamanders, of which there are roughly 400 species alive. Their body plan is generalized with underdeveloped, cartilaginous limb girdles. Size ranges from 4cm (1.5in) to 1.5m (5ft). Distribution is wide over northern hemisphere and scarce over southern. Amongst the salamanders, Paedomorphosis is wide spread and 60% of all salamanders belong to family Plethodontidae . Order Anura (Sacentia)
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This note was uploaded on 04/30/2009 for the course BIO 400 taught by Professor Rebar during the Spring '09 term at Edinboro.

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VertZooNotesDeuce - Vertebrate Zoology Notes Part 2 The...

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