Types of MammalsNB #161

2 Main Groups:

Prototheria: monotremes

Theria: marsupials & placentals

MonotremesEgg laying mammals

◦Retain eggs in their bodies for an extended time

5 species: duck-billed platypus & 4 species of echidnas (spiny anteaters) Short-beaked

echidnaduck-billed platypus

Monotremes“Monotreme”– means “single

opening”◦They have a cloaca instead of an

anus, urethra, & vaginaLive in Australia & New GuineaNo nipples- excrete milk through

mammary glands in the skin◦Display parental care

MonotremesLack teeth as adults (have

molars as young)Spur in the ankle- produces

powerful venom in the male platypus

Bill on the head functions in electroreception

Platypus video

Marsupials (metatherians)Young are carried in a pouchIncludes kangaroos, koalas,

oppossums, wombats, & the Tasmanian devil

kangaroo

Tasmanian devil

koala

MarsupialsMost live in Australia & New

Guinea◦We have one here…. Do you know

what it is?Young are born early and then

climb into their mother’s pouch to fully develop

* The placenta does not develop

Kangaroo baby* Young are called “joeys”

Placental MammalsGive birth to live and developed

young* Nourish young with a

placenta (organ developed during pregnancy for gas exchange, waste elimination, & nutrient uptake)Includes elephants, manatees,

anteaters, cattle, whales, badgers, dogs, & humans

Placental MammalsWith the exception of the

opossum, all mammals native to North America, Europe, Africa, and Asia are placental mammals (eutherians)

Placental MammalsWide opening at the bottom of

the pelvis for large, well-developed offspring

Placental MammalsHippopotamus- large herbivores in

sub-Saharan Africa◦Closely related to whales◦Spend most of their lives in water◦Very aggressive- one of the most

dangerous animals in Africa (humans are their only predators)

Placental MammalsElephant- largest land animal

◦Large proposcis modified into a trunk (mostly used for grabbing items)

◦Incisors grow into tusks used for digging and fighting

Placental MammalsTigers- largest cat species & third

largest land carnivore (behind polar bear & brown bear)◦Now highly endangered due to fur

poaching

Placental MammalsBlue whale- largest animal to

ever exist on Earth (98 feet long & 170 tonnes)◦Teeth modified into large plates

called “baleen”– eat tiny krill◦Endangered due to whaling

Placental MammalsManatees- also called sea cows

◦Large aquatic herbivores Known to wipe out plants from an entire

area

◦Slow moving- often killed by boats◦Sailors used to confuse manatees

with mermaids

Placental MammalsPrimates- lemurs, bush babies, monkeys, gibbons, gorillas,

chimpanzees, & humansOpposable digits on the feet and/or

handsHumans- adapted an upright posture,

ability to use and manipulate tools, bipedal locomotion, & highly complex brains◦ Homo sapiens- our scientific name!!

(evolved as early as 195,000 years ago)