Mammals

Novel adaptations:

-Hair

-Mammary glands

-Sebaceous skin

-Jaw bones and muscles

-Specialized nasal bones

-Specialized teeth

-Ear structure

-Specialized kidney

-Cerebral cortex

-True gestational pregnancy
Hair

  • Keratin protein

  • Under hair: dense and soft, insulation to retain body temperature

    • In aquatic mammal with fur, the under hair is so dense it’s waterproof

  • Guard hair:

    • course and longer, for protection and for coloration

  • Mammals shed 2x a year

  • Sensory information

    • Vibrissae (whiskers, bristles) attach to nerves

      • Sometimes lightly attached quills

  • Camouflage color

  • Communication

    • Protection, warning

Horns and Antlers

  • Bovidae family

    • Bone core, from skull with epidermal layer covering bone and keratin layer covering epidermal

  • True horns:

    • Are not shed

    • Do not branch

    • Grow continuously, both sexes

  • Antlers occur in Cervidae family (deer)

    • Solid bone, covered by velvet

    • Antlers:

      • Are shed

      • Do branch

      • Grow for limited time, in males only

Skin and glands:

  • 2-20

  • Lactations means offspring do not forage on their own, mom supplies nutrition

  • Sebaceous glands

    • Excrete sebum lipids to keep skin/hair soft and pliable

    • Helps waterproof skin

  • Eccrine glands

    • Watery fluid

    • Temperature regulation (perspiration)

      • Evaporation occurs, removes heat from skin

    • Not all have eccrine glands

      • Found in hairless body areas

      • Most primates and horses have them scattered throughout body

  • Apocrine glands

    • Secrete milky odorous fluid

      • Scent glands

      • Used for communication

        • Territory, sexual readiness

    • Develop during sexual maturation

    • Location is species specific: behind the eyes, along the cheek, foot pads, anal region

      • Skunks can discharge secretions from their apocrine glands (6-10 ft)

Jaw and Teeth:

  • Lower jaw compromised of just one bone called the dentary

    • Hinged to the temporal bone

  • Adductor muscles close the jaw, temporalis and masseter, up-down movement and side-side movement

  • Specialized heterodont teeth

  • Different types/shapes of teeth for different function

    • Canines, incisors, premolars, molars

  • Other vertebrates are homodonts

  • Diphyodonts

    • baby teeth and adult teeth

    • Most vertebrates can replace teeth throughout their life

Olfaction and Cerebral Cortex

  • Jacobson

  • Processed by cerebral cortex

  • outermost layer of gray matter

  • voluntary muscle movement, memory, judgement

Feeding Specializations:

  • Insectivores:

    • Insects and other inverts

    • No prolonged fermentation- short intestinal tract

    • Specialized teeth to crush exoskeleton

    • Shrews, moles, bats, anteaters

  • Herbivores

    • Feed on grass and other vegetation

    • No canine teeth, premolars/molars adapted for grinding

    • Digesting cellulose requires specific anaerobic bacteria that produce cellulase

    • Very long digestive tract

      • Non-ruminants: Fermentation occurs either in the colon or cecum

      • Ruminants: Occurs in 4-chambered stomach

    • Eat continuously throughout day