Evolution: from reptiles (a branch called therapsids) ~ 150 mya What event (65 mya) provided mammals a window of opportunity? Common Features of Mammals: 1. Complex Brain allows complex behavior, learning, curiosity. 2. Well Developed Heart Four Chambered Heart Warm Blooded (Endothermy) 3. Well Developed Lungs Air intake aided by what muscle? 4. Skin Glands a.Mammary Glands milk (lactose) b. Sweat Glands Regulate body temperature & get rid of wastes Humans all over Dogs & Cats - paws C. Sebaceous (Oil) Glands Lubricate hair & skin d. Scent Glands communication 5. Hair traps air therefore insulates This is a distinctly mammalian trait. Hair may also function for camouflage or signaling. Aquatic mammals have lost most of their hair (replaced with blubber) 6. Diphyodont Teeth Two sets: Baby teeth & Adult teeth (humans 20, 32) The two traits that make you a mammal? Monotremes Oviparous lay eggs Marsupials Ovoviviparous young develop inside mom (attached to yolk sac) Short gestation Further development in pouch (nipples-milk) Examples of Marsupials: Placental Mammals 95% of all mammals Internal development (viviparous) Longer gestation Fetus-umbilical cord-placenta-uterine wall