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Mammals
Characteristics:
Are mammals ectotherms or endotherms?
How do mammals stay warm?
Hair insulates most mammals
Some marine mammals have a layer of
subcutaneous fat (blubber)
Nutrient intake:
Specialized teeth
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Incisors – biting
Canines - stabbing, holding
molars - crushing, grinding
Different types of mammals have different types of teeth depending on their diet
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Predators have large canines - The canines of
predators are very large and sharp, used for tearing
flesh
Herbivores have large flat molars
Mammals have diverse diets.
Herbivores often have an extra stomach chamber
called a RUMEN to help them digest plants
The rumen holds bacteria that can digest plant
material
Circulation
Mammals have a 4 – chambered heart and double loop
circulation.
What other animals have a double loop?
Movement:
Block:
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Mammals are TETRAPODS, meaning they have four limbs. These limbs can be adapted to
different functions, such as the wings of bats or the flippers of whales.
An animal that is BIPEDAL walks on two legs.
Whales do not have hind limbs, but they do have VESTIGIAL pelvic bones.
Reproduction
Most mammals give birth to live young.
Placental mammals:
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A placenta is attached to the wall of the uterus , it provides the fetus with nourishment.
Mammary glands are only found in mammals. They produce milk to feed young.
Placental Mammals have a gestation period
The exceptions to placental mammals are:
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Order Monotremata:
o Egg laying mammals found only in Australia
o Have reptilian characteristics
(cloaca & egg laying)
o Have mammalian features (hair, mammary gland)
o Examples:
Order Marsupiala
o Mammals bear their young in an immature state, babies develop in a pouch
o Majority are found on Australia, opossums are found on other continents
o Examples:
Biogeography of Mammals
Why do animals on different continents look alike?
Example:
Convergent Evolution: Unrelated species are adapted to similar environments and similar NICHES
Birds
Mammals
Birds reproduction:
Egg:
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Amnion: surrounds only the embryo, inner layer of cells secretes amniotic fluid in
which the embryo floats
Chorion: surrounds all embryonic structures & serves as a protective membrane
Allantois (or allantoic sac): works together with chorion to in respiration and
excretion; important in storage of nitrogenous wastes (uric acid)
General:
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Amniotic egg but has to incubate it (embryo is also an endotherm)
This requires pre-natal nesting behavior
Egg has calcified shell (for sitting on!)
Young born immature: need for post-natal behavior and learning – bigger
cerebrum