PHYS 1010 Lecture Notes - Lecture 3: Monotreme, Marsupial, Hadrosaurid
22 Feb 2019
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Mammals - constant body temp, hair, mammary glands (provide young with milk) Monotreme - non-placental mammals, lay leathery eggs, eg duck-billed platypus. Marsupial - female has ventral pouch surrounding nipples, premature young leave uterus crawl into pouch to complete development eg. opossum and kangaroo. Placental - mammals carry young in uterus until fully developed, placenta ensures efficient nutrition eg. humans, mice. Evidence to support evolution from reptiles to mammals made several times, independently. Evidence suggests marsupial and placental mammals shared a common ancestor. Monotremes history unclear - they may have developed separately. Great reptiles disappeared suddenly and number of mammalian species greatly increased. They spread over the area available - marsupials found in s. america and. These continents were attached via antarctica and separated ~ 55 million years ago. Evidence to support this - fossil marsupial found in antarctica, but no fossils of other mammals found there. Fossils - any form of preserved remains from a living organism.
