Lecture 25 – Vertebrata – Mammalia

Lecture 25 – Vertebrata –...

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Lecture 25 – Vertebrata – Mammalia 1. Distinguishing features 1) Hair – no other group has hair (but not all mammals necessarily have hair because it is a derived characteristic, which means they had it and then they lost it), for warmth 2) Mammary glands – produce milk for young 3) Differentiation of teeth – canines, incisors, premolars, molars; differentiated for different kinds of food 4) Muscular diaphragm – aids in breathing 2. Homoiothermic – warm-blooded, endothermic; we have to maintain a constant body temperature 3. Heart: 4-chambered – 2 auricles and 2 ventricles (no mixing of oxygenated and deoxygenated blood) 4. Separate pulmonary and systemic circulation 5. Sweat glands – to help regulate temperature 6. Nervous system – larger brain, cerebrum, cerebral cortex (our nervous system is the largest and most complex of all the other groups) 7. Fertilization – always internal, but what happens after the egg is fertilized separates
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Unformatted text preview: mammals into three major groups 1) Holotheria monotremes (fig. 31-26) (oviparous) mothers lay eggs and they either have a small pouch or nest; have mammary glands without teats, so milk drips on to fur and baby licks milk off of fur Duck-billed platypus Echidnas (spiny anteater) 2) Metatheria marsupials (fig. 31-27) (viviparous) marsupium (pouch); the young are nourished from a yolk and from some things from the mothers; after a few weeks being inside the mother, the young is expelled from the mother and lives in the sac where is attached to a nipple and gets food that way Kangaroos Koala s Possums 3) Eutheria placental mammals (fig. 3-29) (viviparous); have a placenta (partially from embryo, partially from mother); babies are born at a more mature stage than other mammals (get nourishment from placenta) Humans Zebra Elephants...
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Lecture 25 – Vertebrata –...

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