MONOTREMES “Egg laying” Duckbilled Platypus Anteater Echidna

MARSUPIALS Premature babies develop in pouch Found in Australia/New Guinea Kangaroo Wallaby North America oppossum

PLACENTAL Embryos nourished inside mother by placenta 95% of all mammals are placental http://www.scienceclarified.com/images/uesc_04_img0230.jpg

Ways offspring enter world OVIPARITY- Reproductive tract encloses egg in tough protective shell Eggs deposited outside body to hatch EX: Reptiles & birds & mammals (monotremes)

Ways offspring enter world VIVIPARITY- No shell around egg Eggs retained in body Nourished by mother through placenta Offspring are born alive Ex: mammals & some reptiles

Ways offspring enter world OVOVIVIPARITY- Eggs laid shortly before hatching or hatch inside female Nourishment inside mom comes from egg yolk not mother Ex: Some reptiles (snakes) http://www.naturealmanac.com/archive/hatching_reptile/clutch_of_eggs.jpg

SHELL? NO SHELL? Embryo grows? Food comes from? Seen in? SHELL OVIPARITY OVOVIVIPARITY VIVIPARITY SHELL? NO SHELL? Embryo grows? Food comes from? Seen in? SHELL NO SHELL SHELL OUTSIDE INSIDE INSIDE SHELL EGG EGG MOTHER Birds, Reptiles, Few mammals Mammals, few reptiles Reptiles