MAMMALS_ by xiagong0815

VIEWS: 3 PAGES: 29

									  Phylum CHORDATA
Subphylum VERTEBRATA
   Class MAMMALIA
              MAMMALS!
              Class Mammalia
• Endotherms          •   4-chambered heart
• Produce milk for    •   Specialized teeth
  young               •   Modified limbs
• Hair                •   Highly developed
• Diaphragms              brains
               MAMMALS!
                     Hair is
•   made out of keratin (like feathers)
•   developed from scales (like feathers)
•   arrangement provides insulation /
    waterproofing
•   conserves body heat (endotherms)
             MAMMALS!
       Endotherms maintain constant body
                    temperatures
•   panting (release heat)
•   sweating (release heat)
•   shivering (generate heat)
•   raising hair (conserving heat)
             MAMMALS!
    Mammals have several types of GLANDS
•   Scent
•   Saliva
•   Hormones
•   Milk
•   Digestive enzymes
              MAMMALS!
           Mammals nurse their young
• Mammary glands – secrete milk that is rich
  in fats, sugars, proteins, vitamins, and
  minerals
• This continues until offspring are able to eat
  and digest solid food
             MAMMALS!
     The diaphragm aids in breathing
• muscle beneath the lungs, separating the
  THORACIC (chest) cavity from the
  ABDOMINAL cavity
• Expands the chest cavity, bringing in air
• Contracts and pushes air out
               MAMMALS!
  Mammals have a 4-chambered heart

• Left and Right Atrium
• Left and Right
  Ventricle                 Circulation removes
• Oxygenated and            waste and maintains
                            HOMEOSTASIS
  deoxygenated blood
  are entirely separated.
             MAMMALS!
          Mammalogists love teeth!
• you can tell what an animal eats based on its
  type of teeth
• teeth are adapted to type of food eaten
• teeth are hard and fossilize more often than
  other parts of the body
MAMMALS!
             MAMMALS!
This mole’s pointed incisors are used to grasp
 and hold small prey
MAMMALS!
    A beaver’s incisors
    are modified for
    gnawing and can
    gnaw through almost
    anything.
    These teeth continue
    growing throughout
    the animal’s lifetime.
MAMMALS!
    A lion’s sharp canines
    are perfect for slicing
    and tearing flesh.
           MAMMALS!
Premolars and molars are used for slicing,
shearing, crushing, and grinding.
            MAMMALS!
  Other characteristics include
• modified limbs
• complex behaviors – learning and
  remembering
             MAMMALS!
       Mammals have complex brains
• Primates (including humans) are possibly
  most intelligent
• use tools
• communicate
             MAMMALS!
           3 Orders of Mammals
• Monotremes (platypus and echidnas)
• Marsupials (kangaroos and oppossums)
• Placental Mammals (Chiroptera- bats;
  Rodentia – rodents; Carnivora – weasels,
  skunks, bears, foxes; Cetacea- whales,
  dolphins; Primates- chimps, apes, monkeys,
  humans)
             MAMMALS!
                Monotremes
• Eggs
• Only 3 species alive today (1 platypus, 2
  echidnas)
• Found only in Australia and New Zealand
Flat tail,
duck beak,
webbed feet   Coarse brown hair, covered in spines
             MAMMALS!
                  Marsupials
• short period of development in mother’s
  body
• period of development inside pouch
• most are found in Australia – opossum is
  North American marsupial
               MAMMALS!
               Placental Mammals
•   Over 4000 species (mostly bats and rodents)
•   Young develop in the UTERUS
•   Nourished by a PLACENTA
•   Development inside the mother’s body
    ensures protection from predators and
    environment during development.
           MAMMALS!
The placenta is derived from the same
membranes that surround embryos in
amniotic eggs (reptiles and birds)

Marsupials also have PLACENTAE, but is
short-lived
            MAMMALS!
• smallest mammals are shrews and bats and
  weigh as little as 3 grams
• largest is the blue whale –
  160,000 kg! (352,739 lbs!)
           Origin of Mammals
• The first placental mammals appeared in the fossils
  record about 125 million years ago.

• Scientists trace the
  origins of placental
  mammals from a group
  of mouse-sized animals
  to a group of reptilian
  ancestors called
  therapsids.
           Origin of Mammals
• Therapsids had features of both reptiles and mammals.

• They existed between 270 and 180 million years ago.
           Origin of Mammals
• The mass extinction of the dinosaurs at the end
  of the Mesozoic Era, along with the breaking
  apart of Pangaea and changes in climate, opened
  up new niches for early mammals to fill.


• The Cenozoic Era (65 million years to present) is
  sometimes called the golden age of mammals because
  of the dramatic increase in their numbers and
  diversity.

								
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