Shark Evolution: Difference between revisions
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==Genetics== | ==Genetics== | ||
<b>Phylogeny</b> | <b>Phylogeny</b> | ||
<br>Sharks belong to the taxonomic class Chondrichthyes that contains all cartilaginous fish. Specifically, they are one of two branches of the Elasmobranchii subclass, the other branch being skates and rays. The over 500 known shark species are then broken down into nine orders depending on the number of gill slits and dorsal fins, mouth location compared to eye location, snout elongation, and presence or absence of fin spines, anal fins, and nictating membranes. | <br>Sharks belong to the taxonomic class Chondrichthyes that contains all cartilaginous fish<ref name="1"[link Jorgensen S. Sharks: Ancient Predators in a Modern Sea. Firefly Books Limited; 2013.]</ref>. Specifically, they are one of two branches of the Elasmobranchii subclass, the other branch being skates and rays. The over 500 known shark species are then broken down into nine orders depending on the number of gill slits and dorsal fins, mouth location compared to eye location, snout elongation, and presence or absence of fin spines, anal fins, and nictating membranes. | ||
<br><br><b>Evolution</b> | <br><br><b>Evolution</b> | ||
<br>With the earliest known shark fossils dating back roughly 450 million years ago (1), sharks are one of the oldest living groups of animals. They were most prominent between 350 and 250 million years ago when Chondrichthian species made up over 60% of all fish species, before roughly 96% of all marine life was wiped out during the Permian-Triassic mass extinction (2). Certain early types of sharks survived however, with modern sharks and rays beginning to emerge and diversify around 200 million years ago, starting with cow and frill sharks of the Hexanchiformes (2). | <br>With the earliest known shark fossils dating back roughly 450 million years ago (1), sharks are one of the oldest living groups of animals. They were most prominent between 350 and 250 million years ago when Chondrichthian species made up over 60% of all fish species, before roughly 96% of all marine life was wiped out during the Permian-Triassic mass extinction (2). Certain early types of sharks survived however, with modern sharks and rays beginning to emerge and diversify around 200 million years ago, starting with cow and frill sharks of the Hexanchiformes (2). | ||
Revision as of 02:53, 7 December 2022
Introduction
The evolution of sharks has been long and complex, beginning between 400 and 500 million years ago and spanning multiple mass extinctions to bring us today’s modern sharks. Sharks have evolved a wide variety of fascinating traits that have allowed them to remain as apex predators of the ocean. These physical adaptations have increased their fitness, allowing them to survive and reproduce at greater rates.
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Genetics
Phylogeny
Sharks belong to the taxonomic class Chondrichthyes that contains all cartilaginous fishCite error: Invalid <ref> tag; invalid names, e.g. too many
[1]
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References
- ↑ Bartlett et al.: Oncolytic viruses as therapeutic cancer vaccines. Molecular Cancer 2013 12:103.
- ↑ Lee G, Low RI, Amsterdam EA, Demaria AN, Huber PW, Mason DT. Hemodynamic effects of morphine and nalbuphine in acute myocardial infarction. Clinical Pharmacology & Therapeutics. 1981 May;29(5):576-81.
- ↑ 3.0 3.1 text of the citation
- ↑ Cite error: Invalid
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Edited by Madeleine Campbell, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2022, Kenyon College.
