Mammals
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 HeartWarm Blooded (Endothermy)
3. Well Developed Lungs –
Air intake aided by what muscle?
4. Skin Glandsa. Mammary Glands – milk (lactose)
b. Sweat GlandsRegulate 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 TeethTwo sets:Baby teeth & Adult teeth(humans 20, 32)
The two traits that make you a mammal?
The two traits that make you a mammal?
Monotremes
Oviparous – lay eggs
MarsupialsOvoviviparous – young develop inside mom (attached to yolk sac)Short gestationFurther development in pouch
(nipples-milk)
Examples of Marsupials:
Placental Mammals95% of all mammalsInternal development (viviparous)Longer gestationFetus-umbilical cord-placenta-uterine wall
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