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