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Whale’s Transition from land to the oceans

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

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Whale’s Transition from land to the oceans

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  1. Whale’s Transition from land to the oceans By: Jason Prater

  2. Questions • What environmental factors are responsible for driving this transition? • Evolution of whale hearing?

  3. Cetacea • Whales, dolphins, and porpoises • Characteristics: • Obligate aquatic species • Flippers • Fluke • Vestigial hind limbs

  4. Related Taxa • Artiodactyls

  5. Oldest Known Relative • Indohyus • Found in India • Small deer-like • Wading mammal

  6. Whale Evolution

  7. Whale Evolution

  8. Environmental Influences on the Transition to Water • Cenozoic Cooling • Upwelling of nutrients • Antarctic Circumpolar Current • Flows west to east around Antarctica • Nutrient exchange between Atlantic, Pacific, and Indian Ocean.

  9. Importance of Silica • 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)

  10. Evolution of The Whale Ear • 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.

  11. Evolution of The Whale Ear (cont.) • 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

  12. Literature Cited • 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

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