Proterozoic 1
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Late Protists autotrophs, heterotrophs, or both? occurred with acritarchs (probably planktonic algae floated in water column) most early protests probably planktonic, moved efficiently to find nutrients plankton were abundant by ~ 800 MYA some were benthic (seafloor) and grazed on stromatolites and bacterial mats
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Possible Reasons for the Cambrian Explosion 1. development of skeletons permitted larger body size environmental advantages and prevented predation 2. effective predators evolved, driving diversity development 3. oxygen levels were able to reach high concentrations, perhaps drove the large body size filled ecosystems 4. ecosystems opened by the Snowball Earth event?
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Explosive animal evolution in the last 50 MYA of the Proterozoic 1) trace fossils 2) imprints of soft bodied animals possibly related to jellyfish (Phylum Cnidaria) 3) Ediacaran (Vendian) Fauna (~ 600 MYA) but also included annelid worms and arthropods (crabs, lobsters, insects) skeletal fossils calcium carbonate vase- and tube skeletons
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Anomalocarius canadensis - predators that may have lead to extinction of the Ediacaran Fauna
Early Metazoans Flagellate protests came together to form colonies Next step was metazoans multicellular, specialized cells, soft and/or skeletal framework - probably a protist clade Three initial types of Metazoans: 1. Sponges - good example of early simple form of metazoan (benthic sessile, passive pumping) 2. Cnidarians (Coelenterates) sea anemones, jelly fish and corals, contain nematocysts (stinging cells) and tentacles (defense and food capture), benthic sessile 3. Worms (and all other metazoans, including vertebrates) benthic mobile, body geometry (anterior, posterior, dorsal, ventral, bilateral symmetry), internal digestive system, coelom (internal fluid-filled cavity), circulatory system, filter feeding
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Priapulid wormOttoia prolificaCambrian (543-490 million years ago) The name priapulid comes from "Priapus" the Greek and Roman god of the phallus. Latin brachium ("arm") and Greek pod ("foot").
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The Cambrian Explosion (0.543 BYA) Early Paleozoic life fossil record is all from marine deposits, but it is assumed that protists and fungi inhabited freshwater terrestrial environments by this time First Cambrian fauna overlapped with the Ediacaran fauna Invertebrates exoskeletons Vertebrates - endoskeletons Invertebrate Phyla Porifera sponges Cnidaria jelly fish, corals, anemones Bryozoa lophophore Brachiopods lophophore Mollusca clams, snails Arthropoda crabs, insects, trilobites Echinodermata sea stars, sea urchins, sea cucumbers Hemichordata sea squirts, graptolites
SkeletonsThe evolution of many new animals meant more predators. It also meant more prey. Hard skeletons had advantages for both:Predator (top)The largest predator of the Cambrian seas, Anomalocaris had hard, grasping appendages for seizing prey, and a round mouth lined with sharp, tooth-like plates.Prey (bottom) This trilobite's hard exoskeleton provided armor-like protection from its predator, the anomalocaris.
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BrachiopodDiraphora bellicostataCambrian (543-490 million years ago)Brachiopods use hair-like cilia on an "arm" to draw food and water into their gut.
Brachiopods Eoorthis remnicha Cambrian million (543-490 years ago) Eau Claire, Wisconsin UC16781 The name brachiopod comes from Latin brachium ("arm") and Greek pod ("foot").
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Meaning of the word Reef 1) Derived from the Norse word "rif" which means "human rib" used to describe curved (arcuate) breaking water 2) A "reef" is a sediment accumulation on the seafloor that has topographic expression (relief) 3) A "reef" is a sediment accumulation on the seafloor that is wave resistant, thus creating arcuate breakwaters
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Intermediate Reef of Tabulate and Rugose Coral
Cambrian ocean life This underwater scene is not as strange as it appears at first glance. Look closely and you'll see relatives of many of today's animals--sponges, mollusks, arthropods, and more.
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Horseshoe crabRecent Maryland Uncatalogued Horseshoe crabs and other arthropods have exoskeletons made mostly of chitin, an organic material.
TrilobitePeronopsis interstrictusCambrian (543-490 million years ago) Utah PE57094 Not every trilobite could see. Peronopsis did not have eyes. Scientists think blind trilobites lived primarily in sediments on the ocean floor, or in the deepest, darkest parts of the ocean, where eyes would have been useless.
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Trilobite trailRusophycus clintonensisOrdovician (490-443 million years ago) Ohio UC1267 These are trace fossils--the marks, or traces, of things that were once alive. They are filled-in impressions left after trilobites rested on or moved across the ocean floor. After the trilobites left their marks, sediments filled in the impressions and fossilized.
Molted trilobite tailOrria elegansCambrian (543-490 million years ago) Utah PE6014 Scientists think that trilobite exoskeleton fossils found in fragments, like these, are molted exoskeletons. All arthropods molt: in order to grow larger, they shed their exoskeleton and grow a new, larger one.
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Trilobite Ogygopssis klotziCambrian (543-490 million years ago) British Columbia...