Reproduction in Mammals

Overview Characteristics of Mammals Types of Mammalian Reproduction –Monotremes –Marsupials –Placental Summary

Sexual Reproduction Review Few offspring Genetic variation 2 parents produce haploid gametes Gametes fuse to produce offspring Offspring have characteristics of both parents, but are not identical to each other or to parents Uses meiosis to produce gametes

Characteristics of Mammals Warm-blooded Have hair Produce milk to nourish young High metabolic rates Single bone in lower jaw Three middle ear bones

Monotremes Three living monotremes –Duckbilled platypus –2 species of Echidna (spiny anteater) Echidna. Photo by Dr. Lloyd Glenn Ingles © 2001 California Academy of Sciences.

Monotreme Reproduction Monotremes lay eggs incubated by parents, and nourish underdeveloped young with milk, but have no nipples. Special structures –Eggs, milk, but no nipples encarta.msn.com/media_ /Platypus.html

Marsupials Pouched Mammals Some examples are: –Kangaroos, Koalas, Wombats, Red Kangaroo. Photo by Gerald and Buff Corsi, © 2002 California Academy of Sciences. Wombat. Photo © 2005 Sharon Chester IMAGES/pouch%20baby.jpeg

Marsupial Reproduction Marsupials give birth to live young Offspring are under- developed and continue to grow in pouch, attached to nipple Nourished by milk Special structures –Nipples –Pouch

Placental Mammals (Eutheria) Most mammels reproduce with placenta. A few examples are: - Giraffe, Monkeys, Tiger, Cats, Dogs, Elephants, Humans, etc. Yellow Baboon. Photo by H. Vannoy Davis, © 2002 California Academy of Sciences. encarta.msn.com/medias_ /Mammal.html

Placental Reproduction Placental mammals give birth to live young Young develop in uterus and are nourished by the placenta Long gestation period Nourished by milk through nipples after birth

Placental Special Structures Special structures –Uterus –Placenta –nipples

Quick Review Mammals use sexual reproduction to produce offspring.