Answer: What makes a marsupial, a marsupial? A discussion on the historical biogeography and biological evolution of marsupial mammals. Dr. Robert Voss is a professor at Richard Gilder Graduate School and the American Museum of Natural History. His primary research interests are the evolution of marsupials and the systematics and biogeography of other Neotropical mammals that inhabit moist-forest habitats in Amazonia and the Andes.
What anatomical characteristics distinguish marsupial mammals from placental?
Living marsupials and placentals can be distinguished by a number of anatomical features, including structural differences in their ear regions, teeth, postcranial skeletons, reproductive tracts, and brains. Most people think of pouches when they think about marsupials, but not all marsupials have pouches.
When did these two subclasses of mammals separate from their common ancestor? What do we know about that common ancestor?
The lineages that gave rise to living marsupials and placentals are recognizably distinct in the fossil record as far back as the Early Cretaceous (about 125 million years ago), so the most recent common ancestor of these groups must have lived even earlier. How much earlier is controversial, with some estimates suggesting a date of almost 150 million years (in the Late Jurassic). We don’t know anything about that ancestor for certain, but we assume that it was not unlike the earliest known marsupials and placentals: probably a small climbing (arboreal or semiarboreal) mammal, perhaps superficially resembling living opossums or tree shrews. Because the earliest known marsupial and placental fossils are from China, most paleontologists assume that their most recent common ancestor lived somewhere in eastern Asia.
What is convergent evolution and what are some examples of convergent evolution between marsupial and placental mammals?
Convergent evolution is the appearance of similar traits in distantly related lineages. Examples of convergent evolution between placentals and marsupials are the extinct Tasmanian “wolf” (a very wolflike marsupial), marsupial “moles” (living molelike marsupials that burrow in the sandy deserts of Australia), and kangaroo rats (North American rodents that hop on their hind legs like kangaroos).
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The theoretical percentage of their offspring that will have blood type O is 25 percent
Because they provide new insights in the research for biotechnology and other useful resources to the knowledge of biology.
<span>Transgenic means that one or more DNA sequences from another species has been introduced by artificial means. For example, animals usually are made transgenic by having a small sequence of DNA injected into a fertilized egg or developing embryo. Transgenic plants can be made by introducing foreign DNA into a variety of different tissues.</span>
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In many plants, stomata remain open during the day and closed at night. Stomata are open during the day because this is when photosynthesis typically occurs. Hope this helps. : )
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