Chapter 43Mammals

Section 2Characteristics of Mammals

Endothermy• Allows mammals to live in cold

environments and remain active• Provides energy for strenuous activities

like migrating • Fast metabolism requires more energy• Cold environments- blubber & thick

furred animals

Circulatory System• Two atria and two ventricles• Septum- wall of tissue separates

ventricles• No mixing of deoxygenated and

oxygenated blood• Complete septum- adaptation that allows

mammals’ bodies to transport oxygen more efficiently

Respiratory System• Efficient gas exchange• Large lungs- many alveoli- small sacs

where gas exchange occurs• Expand ribcage and take in air through

lungs• Diaphragm- contraction enlarges thorax

and increases thoracic activity- breathing

Feeding & Digestion• Incisors- cut food• Canines- grip, puncture, & tear• Premolars- shear, shred, cut, or

grind• Molars- grind, crush, or cut• Baleen whales- baleen- thin

plates of keratin- trap prey

Digesting Plants• Cellulose- polymer of sugar

glucose- hard to digest• Stomach- four chambers• One chamber = true stomach• Rumen- another chamber-

contains symbiotic microorganisms

Digesting Plants• Partly digested in rumen, then

regurgitated, chewed again and swallowed again

• Animals may regurgitate multiple times

• Ruminant animals- cows, sheep, goats, giraffes, deer

Digesting Plants• Horses, zebras, rodents, rabbits, &

elephants- cecum • Cecum- large sac that branches from

small intestines and ferments food• Animals with a cecum do not chew

cud

Nervous System• Mammal brain is large• Cerebrum- outer region of brain• Sense organs, movements, behavior,

memory, learning• Vision, hearing, smell, touch, taste• Echolocation- emit high-frequency

sound-waves, which bounce off objects

Development• Mammals develop differently

Monotremes• Lay one to two eggs• Incubate by body heat• Yolk nourishes young• Once young hatch, female feeds

young milk until fully developed

Marsupials• Develop in uterus for short time• When only 2-3 cm, young develop

in mother’s pouch and attach to a nipple to feed

• Young stay in pouch for several months

Placental Mammals• Well-developed young are born

live• Placenta provides nourishment &

oxygen• After birth, infants feed on milk for

several weeks or months

REVIEW!!!• A mammal eats about ten times as

much food as a lizard of the same size. Explain this difference.

• Describe the function of a rumen.