CLASS MAMMALIA

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CLASS MAMMALIA

• Mammalian Characteristics
• About 4500 species of mammals today.
• Mammals have hair, which is used to help maintain
  a warm and constant body temperature.
• Mammals are endothermic, meaning they use
  metabolic energy to regulate body temperature.
• They are named after their mammary glands that
  produce milk used to nourish their offspring.

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• Most mammals are born rather than hatched
  (viviparious). Internal fertilization, embryo
  develops inside the uterus of the mother.
• Mammals have larger brains than other vertebrates
  and are more capable learners.
• Differentiation of teeth. Mammals have a mixture
  of knifelike teeth (incisors) and grinding teeth
  (molars).
• There are three major subclasses of mammals.
  Monotremes (platypuses and echidnas), Marsupials
  (opposums, kangaroos, and koalas), and Placental
  Mammals.

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Monotremes

• Duck-billed Platypus
  Echidnas (spiny anteaters)

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Monotremes

• Monotremes are the only living mammals that lay
  eggs. The egg contains enough yolk to nourish the
  developing embryo.
• Monotremes have hair and produce milk.
• The baby sucks the milk from the fur of the
  mother as she has no nipples.
• Today Monotremes are found only in Australia and
  New Guinea.

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Marsupials
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Marsupials

• Opossums, kangaroos, and koalas are examples of
  marsupials.
• Marsupials are mammals that complete their
  embryonic development in a maternal pouch called
  a marsupium.
• The egg contains yolk that feeds the embryo as it
  begins its development.
• Marsupials are born very early in their
  development. They crawl from the reproductive
  tract to the pouch where they complete their
  development while nursing.
• The opossums of North and South America are the
  only marsupials outside the Australian region.

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Placental Mammals
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Placental Mammals

• Approximately 95 of mammals, including humans,
  belong to the placental mammals.
• Placental mammals complete their embryonic
  development within the uterus, joined to the
  mother by the placenta. What joins the two?
• Placental mammals provide varying degrees of
  maternal care.
• There may be as many as 24 separate orders of
  placental animals. To what order do we belong?

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Primates

• Most primates are tree dwellers.
• Lemurs, tarsiers, and related forms are called
  Prosimians.
• Monkeys, apes and humans are referred to as
  Anthropoids. Anthropoids are further classified
  into New World monkeys, Old World monkeys, and
  hominoids (apes and humans).

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Review Questions

• 1. State the relationship between the time a
  young mammal spends with it's parent and the
  complexity of it's behaviour as an adult.
• 2. Name two characteristics that mammals share
  with birds and two that they do not share.
• 3. What is the function of the placenta? How is
  its structure suited to this function?
• 4. Imagine that you are on a fun ski weekend when
  you discover a frozen specimen of a prehistoric
  terrestrial vertebrate. Because you have an
  unquenchable thirst for knowledge and
  understanding, you absolutely MUST classify it.
  What characteristics would you examine to place
  the specimen in the correct class?
• 5. The muscle that supports the internal organs
  of humans seems to be designed for an organism
  that walks on four legs. What does this suggest?