1. Specialized Teeth, Endothermy, & Hair
Mammals:
Specialized Teeth, Endothermy,
& Hair

2. Speculations…
Mammals began to evolve about 70 mya during the Tertiary period.
The first mammals were small (less than 10cm.) and were nocturnal
They probably looked like little rodents.
Early mammals were thought to have avoided competing with dinosaurs by feeding on insects at night.

3. Characteristics Hair – for camouflage and preventative heat loss
Mammary glands
Specialized teeth
Three middle ear bones

4. Major Orders…
Monotremes – egg laying mammals; viviparous (eggs develop inside)
Marsupials – pouched mammals
Placentals – mammals that carry their babies in a uterus, nourished through the placenta, and give birth to live young Ex. primates

5. Other Important Orders
Ungulates – Hoofed animals
Artiodactyla – even-toed hoofed animals (horses)
Cetacia – whales and porpoises
Some have baleen
Chiroptera – bats
Lagomorphs – rabbits
Pinnepidia – seals and
walruses

6. Teeth
Mammals are called heterodonts because they have teeth specialized for different functions.
Incisors – used for biting and/or gnawing
Canines – used for tearing meat
Premolars – used for chewing
Molars – used for grinding and chewing
Mammals have 2 sets of teeth in their lifetime: deciduous teeth and permanent teeth

7. Vertebral Divisions in Mammals
Unlike birds, our vertebral column is NOT fused
Divided into
Cervical – neck bones; first two are the atlas & the axis
Thoracic – ribs are attached
Lumbar – lower back

8. Circulation
Mammals have a 4-chambered heart, separating the two atria from the two ventricles.
Remember, veins return blood TO the heart, arteries take blood away FROM the heart to the rest of the body; Pulmonary vessels carry blood to and from the lungs.

9. Nutrition & Digestion
Most mammals (including us) currently have, or have had in the past, a cecum; a fermentation pouch full of microorganisms used to digest tough plant matter.
In humans, the cecum has become the appendix.
Some mammals (cows) have chambered stomachs. These chambers are called rumen.

10. Gas Exchange
Mammals are the only animals with a diaphragm, which prompts to enter the lungs.
Instead of air sacs, mammals have alveoli to increase surface area.

11. Nervous System
The size of mammalian brains is considerably large due the increased size of the cerebrum.
Cerebrum allows for more intricate motor, sensory, and intellectual function.