Biology Notes Chapter 33

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Biology Notes Chapter 33

• Mammals

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What Is A Mammal?

• Mammals are endothermic animals, which means they
  are able to generate substantial body heat
  internally.
• Most species are experts at maintaining a
  constant body temperature.
• Mammals use fur, hair and subcutaneous fat to
  conserve body heat
• Many mammals have sweat glands to help cool the
  body.

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What Is A Mammal?

• With the exception of several very primitive
  species that lay eggs, all mammals are
  viviparous.
• Which means that young mammals develop within the
  mother of a time and then are born alive.
• Female mammals have mammary glands, which produce
  milk to nourish young.
• Mammary glands, which give mammals their name are
  probably the most important characteristic that
  scientists use to include an animal in the class
  Mammalia.

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What Is A Mammal?

• Mammals have well developed breathing muscles
  including a diaphragm that separates the chest
  cavity from the abdomen.
• The diaphragm along with other muscles, in the
  chest, pulls air into the lungs by expanding the
  chest cavity.
• Mammals have a four chamber heart, with 2 atria
  and 2 ventricles.

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Evolution of Mammals

• By the end of the Cretaceous period, the mammals
  had split into three groups.
• The most primitive group is the monotremes.
• The most familiar type of monotremes today are
  the duckbilled platypus and the spiny anteater.
• The second group is the marsupials.
• This group contains opossums, kangaroos, wombats,
  and koala bears. These have a pouch that the
  young live in for a short time after birth.
• The third group is the placental mammals.
• This group consists of mice, cats, whales,
  elephants, and humans to name just a few.

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Form and Function in Mammals Feeding

• Carnivorous mammals, such as cats and dogs have
  strong, sharp teeth called incisors and canines
  that are used for biting and ripping flesh.
• Many mammals have sharp claws which they grab
  prey with.
• Herbivorous mammals, such as cows and giraffes,
  eat plants.
• They have evolved strong lips and flat edged
  incisors that grasp and tear tough vegetation.
• They have a chamber in their digestive tract
  called the rumen, where food is processed for a
  time. The rumen contains symbiotic bacterial that
  produce enzymes that break down cellulose.
• After a while they will regurgitate their food
  and re-swallow .
• This is called chewing their cud.

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Respiration

• All mammals, even sea mammals, use lungs, powered
  by two sets of muscles.
• Chest muscles pull air in and push air out by
  moving the ribs up and down to increase and
  decrease the size of the chest cavity.
• When the diaphragm contracts, it pulls the bottom
  of the chest cavity down, further increasing the
  cavity size and causes air to rush into the
  lungs.
• Many mammals are able to use exhaled air to
  vibrate their vocal cords and produce a variety
  of sounds, such as a roar, a bark, or even a
  song.

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Internal Transport

• The mammalian circulatory system is a wondrous
  arrangement of pumps and blood vessels.
• The main pump is a 4 chambered heart which sends
  deoxygenated blood to the lungs.
• After it leaves the lungs it is oxygenated blood
  and returns to the heart, and is pumped through
  the rest of the body via blood vessels.
• The two separate circuits-one to and from the
  lungs, the other to and from the rest of the
  body, efficiently transport gases and nutrients
  to every cell of a mammals body.

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Excretion

• Mammals have the most highly developed kidneys of
  all vertebrates.
• Kidneys extract nitrogenous wastes from the blood
  in the form of urea.
• Urea, water and other wastes form urine.
• Since kidneys are so efficient at controlling the
  composition and levels of body fluids, the
  mammalian kidneys have allowed mammals to live in
  many habitats that could not otherwise have
  inhabited such as deserts.

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Response

• Mammals have the most highly developed brains of
  any animals.
• The brain consists of three parts
• The cerebrum makes complicated behaviors as
  thinking, learning, and even understanding
  possible.
• The cerebellum coordinates movements.
• The medulla regulates body functions such as
  breathing and heart rate, which are not under
  conscious control

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Response Continued

• Mammals depend on highly developed senses to
  provide themselves with information about their
  external environment.
• Certain mammal species have well-developed senses
  of sight, hearing, and smell.
• With the exception of apes, monkeys, and humans,
  most mammals do not see color well

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Movement

• Mammals have various ways to get around.
• Running mammals like a horse, can achieve high
  speeds on level ground.
• Climbing mammals like a monkey, have hands and
  feet with flexible digits that can grasp vines
  and branches.
• Flying mammals, like bats, have arms modified to
  support flaps of skin that form wings.
• Aquatic mammals such as dolphins have arms
  modified into flippers, which they use to control
  their speed and direction in the water.

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Reproduction

• The three groups of mammals differ greatly in
  their methods of reproduction.
• Egg-laying mammals, the monotremes, are the most
  primitive mammals and reproduce much like
  reptiles.
• Monotremes such as the duckbill platypus are
  oviparous. (Egg layers) After they are hatched,
  they feed on mothers milk.

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Reproduction Continued

• Marsupials are viviparous, and bear their young
  alive.
• The fertilized egg grows into an embryo inside
  the mothers reproductive tract.
• The embryo is supplied with nourishment by a yolk
  sack on the egg.
• The yolk is not large enough to carry the baby to
  full development so it is born premature and then
  it will go inside the mothers pouch (the
  marsupium) to finish development.

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Reproduction Continued

• The early stages of placental embryos are much
  like those of marsupials.
• In placental mammals, the embryos chorion,
  amnion, and allantois develop differently.
• Tissues from these membranes join with tissues
  from the mothers uterus to form an organ called
  the placenta.
• Nutrients, oxygen, and carbon dioxide, and wastes
  are exchanged between embryo and mother through
  the placenta.
• The time the embryo spends inside the uterus is
  called the gestation period.

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Important Orders of Living Mammals

• Scientists use several important characteristics
  to classify mammals.
• The structure of teeth and the number and kinds
  of bones in the head are two important features
  by which mammals are classified.
• Perhaps the most important characteristic used to
  classify mammals is the method of reproduction.

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Order Insectavora

• This order contains the insect eaters.
• This order contains tree shrews, hedgehogs,
  shrews, and moles.

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Order Chiroptera

• This order contains the many different species of
  bats which in fact account for one quarter of all
  mammal species.
• Bats are closely related to insectivores.
• Some bats eat only insects, whereas some feed on
  blood or fruit.

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Order Edentata

• The name of this order means without teeth, even
  though some of the mammals in this group may have
  small teeth.
• Members of this order include animals such as
  sloth's, anteaters, and armadillos.

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Order Rodentia

• This order includes many amusing mammals as well
  as many destructive ones.
• Mice, rats, squirrels, beavers, porcupines and
  gophers are all rodents.
• Rodents have two large front teeth for gnawing

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Order Lagomorpha

• Rabbits comprise this order.
• This order resembles the rodents, but are not
  rodents.
• The cotton tail and the jack rabbit are the most
  familiar types of rabbits.

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Order Carnivora

• Carnivores are meat eaters.
• Cats, dogs, wolves, bears, weasels, hyenas, and
  seals are all in this order.

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Order Cetacea

• This order contains the truly aquatic mammals,
  whales, dolphins, and porpoises.
• These animals breath air through the use of lungs
• All members of this order are carnivores.

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Order Artiodactyla

• This order contains the large grazing animals
  like cattle, sheep, goats, hippopotami, giraffes
  and pigs.
• The Artiodactyls are called even toed ungulates.
• The word ungulates means hoofed animal.

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Order Perissodactyla

• Horses, zebras, tapirs, and rhinoceroses belong
  to this order.
• These are the odd toed ungulates.

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Order Primates

• This order includes us.
• This order has the most highly developed cerebrum
  and the most complicated behaviors.
• This order also includes, lemurs, monkeys, chimps
  or apes.