Pelagic

... Porthero and Lazarus, 1980, Planktonic microfossils and the recognistion of ancestors, Systematic Zoology 29:119-129; Lararus, 1983, Speciation in pelagic Protista and its study in the microfossil record: a review, Paleobiology 9:327-340. The horse series in North America also shows examples of ...

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... a decent level of instability. What you will find, however, is that organisms which are well-adapted to very stable parts of the environment (like pelagic sharks or horseshoe crabs) tend to have much better mutation-repair chemistry. For them, mutational variation is non-adaptive. That makes sense. ...

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... a decent level of instability. What you will find, however, is that organisms which are well-adapted to very stable parts of the environment (like pelagic sharks or horseshoe crabs) tend to have much better mutation-repair chemistry. For them, mutational variation is non-adaptive.

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... usually well-adapted to some microenvironment that has remained stable over long periods of time, such as horseshow crabs in surf environments, or pelagic sharks, or lots of tiny organisms. But all we know is that the physically resemble their ancestors - how much they may have changed chemically ...

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When you read "most sharks," remember that it translates to "most pelagic sharks," which are the sexy ones. There are lots of benthic sharks which have pumping gills and don't need to keep moving. No idea how they sleep, though.

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