BIO 200 Lecture Notes - Lecture 23: Mesozoic, Echidna, Convergent Evolution
13 Nov 2017
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Bio200 jessica poulin lecture 23: 5,500 species of mammals, why do mammals have a winning design> Mammals get very big; we are cute. Ancient mammals are mostly small, shrew-like, insectivorous, arboreal and nocturnal: mammals likely survived the extinction of the dinosaur due to endothermy. Mammals are unified by five traits: (plus a few sub traits: hair. Used as a camouflage (predators of orange antelopes are colorblind antelopes in grass are not easily seen by colorblind predators) can be sensory. Defensive (hedgehog, echidna, porcupine: mammary glands. Produce milk (milk changes as the baby grows: endothermy. Allowed animals to survive in extreme temperatures (can control body temperatures) (homoplasious in mammals and birds: sweat glands. Cool mammals via evaporation: four-chambered heart. Marsupials give birth to highly underdeveloped young. Eutherians give birth to highly developed young. Marsupials often have pouches (wombat, yapok, wallaby) no shell develops. > baby latches on in pouch (australia and south america)
