Mammals:

1
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.