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Whale’s Transition from land to the oceans. By: Jason Prater. Questions. What environmental factors are responsible for driving this transition? Evolution of whale hearing?. Cetacea. Whales, dolphins, and porpoises Characteristics: Obligate aquatic species Flippers Fluke - PowerPoint PPT Presentation
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By: Jason Prater
What environmental factors are responsible for driving this transition?
Evolution of whale hearing?
Whales, dolphins, and porpoises Characteristics:
Obligate aquatic species Flippers Fluke Vestigial hind limbs
Artiodactyls
Indohyus Found in India Small deer-like Wading mammal
Cenozoic Cooling Upwelling of
nutrients
Antarctic Circumpolar Current Flows west to east
around Antarctica Nutrient exchange
between Atlantic, Pacific, and Indian Ocean.
Building of cell walls, or frustules, in diatoms Increased diatom diversity in Cenozoic Era
Diatoms Unicellular Producers One of the Most common types of phytoplankton Eaten by Krill
Krill then eaten by whales Short food chain (efficient in supporting apex
predator)
Evolved very quickly Pakicetids (basal cetacean group)
Similar to land mammals External auditory meatus tympanic
membrane middle ear ossicles inner ear fluid Fails under water.
Remingtonocetids and Protocetids Combination of pakicetids and modern
odontocetes Sound transmitted to middle ear by large
mandibular fat pad Presence of external auditory meatus
But poor reception of airborne sound Basilosauroids
Addition of air-filled sinuses between ear and skull Still contained external auditory meatus even
though they were obligate marine animals. Modern Odontocetes
Loss of external auditory meatus
Sirpa Nummela, J.G.M. Thewissen, Sunji Bajpai, S. Taseer Hussain and Kishor Kumar. Eocene Evoluiton of Whale Hearing. Nature 430, 776-778. 2004.
Bajpai, S. Thewissen J.G., Sahni, A. The origin and early evolution
of whales: macroevolution documented on the Indian subcontinent. Journal of Bioscience. Nov. 34(5):673-686, 2009.
J.G.M. Thewissen, L.N. Cooper, M.T. Clementz, S. Bajpai and B.N. Tiwari. Whales originated from aquatic Aritiodactyls in the eocene epoch of India. Nature 450, 1190-1194. 2007
Marx, F.G. and M. Uhen. Climate, critters, and cetaceans: Cenozoic driers of the evolution of modern whales. Science 327, 993-996, 2010.
Berger, W.H. Cenozoic cooling, Antarctic nutrient pump, and the evolution of whales. Oceanograhy. 54, 2399. 2007