The Evolution of Fish: Vertebrates Begin
The Evolution of Fish: Vertebrates Begin
If you were to look at the oceans 530 million years ago, you would be amazed by the wild array of creatures thriving in the waters. The seas abound with robust rainbows of corals and starfish. Huge schools of jellyfish pump through the waters while the sea floor is alive with a variety of mollusks and crustaceans. Life would likely have appeared to be as diverse as it could get. Then in the waters off the coast of China appeared a new, tiny little creature: Myllokunmingia fengjiaoa.[1]
In the late-1990s, Chinese scientists found this 3-centimeter long little organism in the rocks of the Yunnan province.[2] Although only one single example of this organism has ever been found[3], it has been identified by some as the start of a huge new branch on the tree of life: The vertebrates. It is proposed that from this small little creature – which is the first to have displayed a notochord and dorsal nerve cord – the entire array of vertebrate sprang: Fish and eventually reptiles (and birds), amphibians, and mammals.
So before you can understand how the world of fish came to be, you must start with these early ancestors. Vertebrates are members of the phylum Chordata. These chordates share three key characteristics in common:
Notochord: A flexible, longitudinal rod present in all vertebrate embryos and some adults. This device served as an early “backbone” for this family of creatures. [4]
Pharyngeal Slits/Clefts: These small pouches/openings in the body of the organism to allow the water taken in to exit the body. In fish, these are now called “gills.” Later in the evolutionary universe, these pouches would evolve into lungs for the land-living vertebrates.[5]
Muscular, Post-Anal Tails: Although in some species, the post-anal tail is so small to be noticed, all chordates possess a tail that extends posterior to the anus.
The early chordates started as lancelets and tunicates.
If you were to look at the oceans 530 million years ago, you would be amazed by the wild array of creatures thriving in the waters. The seas abound with robust rainbows of corals and starfish. Huge schools of jellyfish pump through the waters while the sea floor is alive with a variety of mollusks and crustaceans. Life would likely have appeared to be as diverse as it could get. Then in the waters off the coast of China appeared a new, tiny little creature: Myllokunmingia fengjiaoa.[1]
In the late-1990s, Chinese scientists found this 3-centimeter long little organism in the rocks of the Yunnan province.[2] Although only one single example of this organism has ever been found[3], it has been identified by some as the start of a huge new branch on the tree of life: The vertebrates. It is proposed that from this small little creature – which is the first to have displayed a notochord and dorsal nerve cord – the entire array of vertebrate sprang: Fish and eventually reptiles (and birds), amphibians, and mammals.
So before you can understand how the world of fish came to be, you must start with these early ancestors. Vertebrates are members of the phylum Chordata. These chordates share three key characteristics in common:
Notochord: A flexible, longitudinal rod present in all vertebrate embryos and some adults. This device served as an early “backbone” for this family of creatures. [4]
Pharyngeal Slits/Clefts: These small pouches/openings in the body of the organism to allow the water taken in to exit the body. In fish, these are now called “gills.” Later in the evolutionary universe, these pouches would evolve into lungs for the land-living vertebrates.[5]
Muscular, Post-Anal Tails: Although in some species, the post-anal tail is so small to be noticed, all chordates possess a tail that extends posterior to the anus.
The early chordates started as lancelets and tunicates.
Cited: Campbell, Neil A., et al., Biology, 8th Ed., San Francisco: Pearson Benjamin Cummings, 2008. [5] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 700 [6] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 702 [7] http://www.hoxfulmonsters.com/2009/08/knowing-craniates-craniata-animals-with-skulls/ [8] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 702 [9] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 703 [10] http://www.hoxfulmonsters.com/2009/08/knowing-craniates-craniata-animals-with-skulls/ [11] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 704 [12] http://en.wikipedia.org/wiki/Gnathostomes [13] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 707 [14] Campbell, Neil A., et al., Biology, 8th Ed., (San Francisco, Pearson Publishing 2008), p 710