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Amphibia

Amphibia. Moist skin Eggs laid in water; External fertilization Aquatic larvae with gills metamorphose into air-breathing adults. Amniote Egg. Allows fully terrestrial life. Waterproof shell. Reservoir of water inside the egg. Fertilization is internal, before the shell forms.

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Amphibia

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  1. Amphibia Moist skin Eggs laid in water; External fertilization Aquatic larvae with gills metamorphose into air-breathing adults

  2. Amniote Egg • Allows fully terrestrial life. • Waterproof shell. • Reservoir of water inside the egg. • Fertilization is internal, before the shell forms. • (Later, some animals in the amniote lineage evolved the ability to retain the egg internally, never developing a shell, and giving birth to live young.) • Other features of Amniote animals: • Waterproof skin • Ability to excrete concentrated urine, in order to conserve water.

  3. Reptiles • Waterproof eggs • Dry scaly skin • Heart with 3½ or 4 chambers

  4. “Reptilia” is paraphyletic • All reptiles evolved from one common ancestor. • But the “Reptilia” (as usually defined) do not include all descendants of that ancestor. • Birds are an offshoot of thereptilian lineage. • In a truly phylogeneticclassification, there would be no class Aves; birds would be part of theReptilia.

  5. Aves – The BirdsTraditionally a Class, but better recognized as a Subclass of Reptiles • Scales modified into feathers • 4-chambered heart • Endothermic (warm-blooded)

  6. Class Mammalia • Endothermic, possess fur, females secrete milk • Subclass Protheria (monotremes) lay eggs (Platypus and Echidna) • Subclass Theria give birth to live young. 2 groups: • Marsupialia have very limited nutrition of young before birth, but nurture them in a pouch after birth. • Eutheria have a placenta to give nutrition in the uterus, and give birth to well-developed young.

  7. Some representative Eutherian orders • Rodentia – rodents (the largest order) • Chiroptera – bats (second largest) • Carnivora – cats, dogs, bears • Artiodactyla and Perissodactyla – hoofed animals • Primata – Primates (lemurs, monkeys, apes)

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