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Evolution of Whales: From Land to Water. Catie Willard and Lindsey Baumoel. Question???. How have whales physiologically evolved from land to water?. Whale Video. Pakicetus. Three genera: Pakicetus , Nalacetus , and Ichthyolestes Eocene Kuldana Formation of Pakistan

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evolution of whales from land to water

Evolution of Whales: From Land to Water

Catie Willard and Lindsey Baumoel

question
Question???

How have whales physiologically evolved from land to water?

Whale Video

pakicetus
Pakicetus
  • Three genera: Pakicetus, Nalacetus, and Ichthyolestes
  • Eocene Kuldana Formation of Pakistan
  • Evidence of Fossils
ambulocetus
Ambulocetus
  • 47-48 million years ago
  • Well developed fore- and hind-limbs
  • Swam by pelvic paddling
  • Hind feet large, with elongated, flattened toes suggesting webbed feet and the ability to walk on land
dorudon
Dorudon
  • Late-middle Eocene
  • Smaller dolphin-sized animals
  • Skeletal morphology of caudal region
  • No sacrum and floating pelvis
basilosaures
Basilosaures
  • 40 to 34 million years ago
  • Hind limbs to short to support body mass
  • 18 meters (60 feet)
  • The hind limbs had fused tarsals
  • Absence of articulation
  • Possible functions of limbs
mysticeti and odontoceti
Mysticeti and Odontoceti
  • Miocene
  • Have baleen teeth used for filter-feeding
  • Very large and do not dive to great depths
  • Typically smaller than baleen whales
  • Have teeth
  • Swim rapidly and dive deep
molecular evidence
Molecular Evidence
  • Five mitochondrial DNA sequences and eleven nuclear-encoded protein sequences aligned from Cetacea, two Artiodactyl suborders and an outgroup
  • Cetacean DNA sequences from Finback Whale
  • Protein sequences come from different whales depending on who the sequence was known for in each of the eleven proteins
  • Maximum parsimony and maximum likelihood where the methods of reconstruction used for alternative phylogenetic trees
  • Only transversions were looked at for the DNA sequences
molecular evidence9
Molecular Evidence
  • PROTPARS was used to calculate the number of amino acid replacements required for each alternative tree
  • The reliability of these tests was determined by bootstrap re-sampling of parsimony and several other tests; for DNA sequences the max-likelihood trees were also tested by bootstrap re-sampling
results
Results
  • Tree one is the presently accepted taxonomic scheme
  • The DNA data using max parsimony and max likelihood combined with bootstrap resampling gives tree II
  • For protein sequences the traditional tree was not supported by any of the tests; the only significant support was for tree II
works cited
Works Cited
  • Bejder, Lars and Brian K. Hill. 2002. Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss. Evolution and Development. 4(6): 445-458.
  • Gingerich, Philip D. 2003. Land-to-sea transition in early whales: evolution of Eocene Archaeoceti (Cetacea) in relation to skeletal proportion and locomotion of living semiaquatic. Paleobiology. 29(3): 429-454.
  • Gingerich, Philip D. 1998. Paleobiological perspectives on Mesonychia, Archaeoceti, and the origin of whales. Paleobiology. 423-446.
works cited cont d
Works Cited cont’d
  • Graur, D. and Higgens, D. 1994. Molecular evidence for the inclusion of cetaceans within the order artiodactyla. Mol. Biol. Evol. 11(3): 357-364.
  • Thewissen, J. G. M., Hussain, S. T., and Arif, M. 1994. Fossil evidence for the origin of aquatic locomotion in Archalocete whales. Science. 263(5144): 210-212.
  • Thewissen, J. G. M, Williams, E. M., Roe, L. J., and Hussain, S. T. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature. 413: 277-281.