Difference between revisions of "Whale"
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| − | + | The term whale refers to all [[Cetacean|Cetaceans]] that are not [[dolphin|dolphins]] or [[Poprpoise|porpoises]] or more informally to only the very largest [[Cetacean|Cetaceans]]. Although whales are famed for the massive size reached by some species, like the largest animal to ever live the [[Blue Whale]], others are relatively small like the pygmy right whale which grows to about 20 feet <ref> American Cetacean Society website [http://www.acsonline.org/factpack/PygmyRightWhale.htm]</ref>. Though whales have many traits in common with fish (including fins and tails) they are in fact mammals and accordingly breath air and lactate. Whales have a number of remarkable [[adaptation|adaptations]] including: | |
* they decide when to breathe, rather than breathing unconsciously | * they decide when to breathe, rather than breathing unconsciously | ||
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* they have massive brains, much larger than the brains of other mammals | * they have massive brains, much larger than the brains of other mammals | ||
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| + | == Evolution and taxonomy == | ||
| + | The question of how whales and their relatives could have evolved from terrestial [[mammall|mamalls]| has taxed evolutionary biologists since [[Darwin|Darwin's]] suggestion that may have evolved from ancient bears. In more recent times molecular and fossil evidence has combined to suggest that modern whales and their relatives arose from ancient [[Artiodactyla|artiodactyls]] (even-toed ungulates) with the cloest living relative of all whales being hippos<ref> Theodore, JM (2004) Molecular Clock Divergence Estimates And The Fossil Record Of Cetartiodactyla <i> The Journal Of Paleontology 78:39-44[http://www.redorbit.com/news/science/41080/molecular_clock_divergence_estimates_and_the_fossil_record_of_cetartiodactyla/index.html]</ref>. This kinship has been termed the whippo hypothesis. Evolutionary biologists believe the last commen ancestor of whales and hippos lived about 25 million years ago <ref> UCLA berkley "Understanding Evolution for Teachers" website [http://evolution.berkeley.edu/evosite/lines/IAtransitional.shtml]</ref>, which is contrast with the [[Young earth creationism|young earth creationist]] position that that whales were [[creation|created]] about 4000 years ago when [[God]] created the [[earth]]. | ||
== References == | == References == | ||
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<references/> | <references/> | ||
[[Category:Mammals]] | [[Category:Mammals]] | ||
Revision as of 05:33, March 21, 2007
The term whale refers to all Cetaceans that are not dolphins or porpoises or more informally to only the very largest Cetaceans. Although whales are famed for the massive size reached by some species, like the largest animal to ever live the Blue Whale, others are relatively small like the pygmy right whale which grows to about 20 feet [1]. Though whales have many traits in common with fish (including fins and tails) they are in fact mammals and accordingly breath air and lactate. Whales have a number of remarkable adaptations including:
- they decide when to breathe, rather than breathing unconsciously
- they sleep 8 hours a day, yet need to be conscious to breathe
- they can communicate with each other by making remarkably loud noises
- these extraordinary noises can travel for miles under water
- the females nurse their calves while swimming underwater
- the males have a unique cooling system for their internal reproductive organs
- some have two blow-holes, but others only have one
- the blow-holes pass air above water, yet resist intense pressure underwater
- they have massive brains, much larger than the brains of other mammals
Evolution and taxonomy
The question of how whales and their relatives could have evolved from terrestial [[mammall|mamalls]| has taxed evolutionary biologists since Darwin's suggestion that may have evolved from ancient bears. In more recent times molecular and fossil evidence has combined to suggest that modern whales and their relatives arose from ancient artiodactyls (even-toed ungulates) with the cloest living relative of all whales being hippos[2]. This kinship has been termed the whippo hypothesis. Evolutionary biologists believe the last commen ancestor of whales and hippos lived about 25 million years ago [3], which is contrast with the young earth creationist position that that whales were created about 4000 years ago when God created the earth.