m a m m a l s

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m a m m a l s
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diversity of
the
mammalian
world
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class mammalia ? 24 orders
? 4400 species
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Mammals can be found on every continent,
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Mammals can be found on every continent,
and in every ocean!
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Mammals first
appear early
in the TRIASSIC period
?
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"The picture's pretty bleak, gentlemen .....
the world's climates are changing, the mammals
are taking over, and we all have a brain about
the size of a walnut."
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SIX KEY CHARACTERISTICS OF MAMMALS
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Endothermy
The tendency to maintain a relatively
constant internal body temperature
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Endothermy makes SUSTAINED ACTIVITY possible
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BODY HAIR
What are its FUNCTIONS?
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COMPLETE 4-CHAMBERED HEART
This is REQUIRED for ENDOTHERMY.
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The heart in action
http//www.youtube.com/watch?vH04d3rJCLCE
http//www.youtube.com/watch?vD3ZDJgFDdk0feature
related
http//www.youtube.com/watch?viX6HnUyzgQ0feature
related
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UNIFIED MANDIBLE
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arthropod mandibles
this ? permits OMNIVORISM
?
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FEMALES NURSE YOUNG WITH MILK FROM MAMMARY GLANDS
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SPECIALIZED TEETH
alligator
barracuda
possum
human
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GROUPS OF MAMMALS

• ? Monotremes
• ? Marsupials
• ? Placentals

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MONOTREMES
Short-beaked echidna Tachyglossus aculeatus
Duck-billed platypus Ornithorhynchus
anatinus
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MONOTREMES
? Egg-laying mammals
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Young are born very underdeveloped
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MARSUPIALS
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Approximately 200 species
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? Marsupial mammals young are partially
developed at birth so they must be
carried in pouches of their mothers
until they are sufficiently
developed
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PLACENTALS
There are TEN ORDERS of placental mammals. 95
of all mammals are placentals
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A vascular organ in most mammals that unites the
fetus to the uterus of the mother. It mediates
the metabolic exchanges of the developing
individual through an intimate association of
embryonic tissues and of certain uterine tissues,
serving the functions of nutrition, respiration,
and excretion.
placenta
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Placental mammals are more highly-developed at
birth because of placentation
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Human placenta shown a few minutes after birth.
The side shown faces the baby with the umbilical
cord (top right). The unseen side connects to
the uterine wall. The white fringe surrounding
the bottom is the remnants of the amniotic sac.
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BE SURE TO KNOW THE STUCTURE AND FUNCTION OF
THE 4-CHAMBERED HEART
know mamm. heart and 12 orders in book