哺乳动物的繁殖介绍【英文】

• Lays eggs, parent incubates • Special structures
– Eggs, milk, but no nipples
Echidna. Photo by Dr. Lloyd Glenn Ingles © 2001 California Academy of Sciences.
– Nipples – Pouch
Red Kangaroo. Photo by Gerald and Buff Corsi, © 2002 California Academy of Sciences.
Wombat. Photo © 2005 Sharon Chester
• Include Kangaroos, koalas, wombats,
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Quick Review
• Marsupials bear live young • Offspring are underdeveloped and continue to grow in pouch, attached to nipple • Nourished by milk
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http://www.ucmp.berkeley.edu/mammal/mammal.html
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Monotremes
• Three living monotremes
– Duckbilled platypus – 2 species of Echidna (spiny anteater)
Yellow Baboon. Photo by H. Vannoy Davis, © 2002 California Academy of Sciences.
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Quick Review
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Characteristics of Mammals
• Warm-blooded • Have hair • Produce milk to nourish young • High metabolic rates • Single bone in lower jaw • Three middle ear bones
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Placental Mammals (Eutheria)
• Give birth to live young • Long gestation period, young develop within uterus, nourished by placenta • Special structures – Uterus – Placenta – nipples
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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
http://www.ucmp.berkeley.edu/mammal/monotreme.html
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Marsupials
• Pouched Mammals • Live birth, but young are born underdeveloped • Crawl from birth canal and latch onto nipple, continue to develop in pouch. • Special structures
• Mammals use sexual reproduction to produce offspring.
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Байду номын сангаас
Quick Review
• Monotremes lay eggs incubated by parents, and nourish underdeveloped young with milk, but have no nipples.
Reproduction in Mammals
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Overview
• Characteristics of Mammals • Types of Mammalian Reproduction
– Monotremes – Marsupials – Placental
• Summary
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http://www.wfcr.org/OLD_WWW/opossuminfo.html
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Quick Review
• Placental mammals bear live young • Young develop in uterus • Long gestation period • Nourished by milk through nipples