Mammals can be classified by:
tooth structurebones in the headmethods of
reproduction and developing
Three groups of living mammals:
• Monotremes
• Marsupials
• Placentals
• Lay eggs• Digestive, reproductive,
and urinary systems open into a cloaca, like a reptile
• Monotreme means “single opening”
• Eggs are incubated outside of the body
• Young monotremes are nourished by their mother’s milk, licked from pores on the surface of her abdomen
• Only three living species: duckbill platypus, and two species of spiny anteaters, or echinadas
• Found in Australia and New Guinea
Perry the Platypus
is a
monotreme!
• Bear live young at a very early stage of development
• Usually completes development in an external pouch, or a marsupium, on the mother’s body
• Marsupials are named after this structure
• Lives in pouch several months, drinking the mother’s milk and growing
Opossum
Koala
Kangaroo
• Named after their internal structure, the placenta, which is formed when the embryo’s tissues join with tissues from within the mother’s body
• Usually after birth, the mom cares for their young
• Nutrients, oxygen, carbon dioxide, and wastes are exchanged between embryo and mom through the placenta, allowing the embryo to develop much longer than a marsupial (pg. 830-831 in your textbook shows the order of placental mammals.)
Elephant
Shrew
Whale
• Mouse/ Rat ………………...............• Rabbit ………………………………………….........• Dog ………………………………………………• Horse …………………………………………………• Elephant …………………………………………….• Whale …………………………………………....• Cow……………………………………………• Giraffe……………………………………….• Human …………………………………………………
Between 18-21 Days28-31 Days
About 62 Days11 Months22 Months
10-14 MonthsAbout 9 Months
About 15 Months9 Months
• When the continents separated into different parts of the world, the animals there adapted to their environment.
• Similar ecological opportunities on the different continents have produced some examples of convergent evolution in mammals. (pg 832)