BIO 1300 Lecture Notes - Lecture 4: Stratum Spinosum, Stratum Corneum, Muscular Layer
12 Feb 2018
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Document Summary
Vertebrate tetrapod (4-legged creatures) we are bipedal versions of them. Evolution of tetrapods from fish to amphibian. Amphibians live in both aquatic and terrestrial they lack features that allow them to live permanently on dry land. No internal fertilization or dry eggs so they are limited to water. Skin is permeable (can absorb and transmit liquids and substances through it) highly susceptible to desiccation (this is also how they breathe) Reptiles dominant animals or 200my- have what was absent in the amphibians (internal fertilization, shelled egg, and a scaly impermeable skin) Scaly skin helped them dominate on the hot dry lands of pangea. Does not let water vapor go through and gas flow (do not breathe through their skin) can maintain body moisture without losing it (good for living on dry land) Keratin is an important protein to skin of vertebrates because the extensions of all vertebrate skin are made of keratin (nails, scales, beaks, feathers, hair)
