LECTURE 4: PALEOZOIC ERA Cambrian/Ordovician Periods

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What Life existed in the Early Cambrian Period (543 mya)? Late Precambrian Period Ediacaran Fauna Limited Diversity Early Cambrian Period (543-530 mya) The “small, shelly fauna” First Appearance of skeletalized parts: tiny plates, cones, and tubes. Made of various minerals Plant life is essentially limited to Algae

Timeline of Cambrian Events (543 mya – 500 mya) 530 mya – Cambrian Explosion 8 animal phyla Porifera (sponges) Cnidaria (jellyfish, corals) Platyhelminthes (flatworms) Arthropods (Trilobites) Mollusks (bivalves/gastropods/nautiloids) Echinoderms (Sea Stars) Annelids (worms, leeches) Chordates (spinal tube/Graptolites?) 500 mya – First Vertebrate First Jawless fish: Myllokunmingia By the end of the Cambrian: Trilobites DOMINATE

Make a cladogram Lab?

What was the Cambrian Explosion? most animals appear in a relatively BRIEF time in history (~530-520 mya) great diversity of marine invertebrates All 8 animal phyla first appear in the fossil record: hard parts flourished all of the eight major animals body plans in existence today, along with 27 minor ones, had emerged and no new body plans have developed since

What Animals appear in the Cambrian Explosion? Porifera (sponges) Cnidaria (jellyfish, corals) Platyhelminthes (flatworms) Arthropods (Jointed appendages, segmented bodies ) Mollusks (bivalves/gastropods) Echinoderms (Sea Stars) Annelids (worms, leeches) Chordates (spinal cord)

What Trace Fossil marks the Beginning of the Cambrian Period? Trichophycus pedum Burrowing animal No hard parts

What is the Burgess Shale? Rocky Mountains of British Columbia Discovered in 1899 It is 505 million years old Celebrated for its preservation of soft parts Showed that Trilobites Dominated!!

Burgess Shale Fauna

Canapaptsis Hallucigenia Wapatia

Pikaia (earliest chordate)

Anomalocaris Wiwaxia Opabinia

Why did the Cambrian Explosion Occur? Increased Oxygen in the atmosphere At low O2 levels, only simple metabolic tasks can occur At high O2 levels, more energy can be exerted to other tasks Skeletonization Low 02 levels, only small, soft bodied forms Allows larger body size- predator-prey relationship Predator-Prey Arms Races First Predators arose during Cambrian (Flatworms) This led to selection of diverse hunting adaptations Heavily Armored prey Shells in guts of large predators

What was the First Vertebrate What was the First Vertebrate? First Jawless fish: Myllokunmingia 500 mya Ancestor to Living Jawless Fish (Lampreys)

What Significant Event Happened at the end of Ordovician Period (500 mya- 439mya)? MASS EXTINCTION #1 (439 mya) At least 70% of all species were wiped out. Many species of trilobites, brachiopods, echinoderms, graptolites, and corals became extinct

Why did the Mass Extinction Happen? Global Cooling Gondwana moved over the South Pole, causing glaciers to form and global temperatures to cool. Many species could not survive cooler conditions Suffered from habitat loss as water turned to ice, lowering sea levels worldwide.

What did the Continents Look Like? Continental Drift Animation Continent Animation 600 mya to 50 mya

PALEOZOIC (543-245 mya) 543 billion- Ozone Layer forms 543 CAMBRIAN EXPLOSION begins 480-250 million- Cambrian - 1st vertebrates appear (Jawless Fishes) Ordovician- 1st Mass Extinction Silurian- 1st land plants are ferns and mosses (non-vascular) 1st land animals are amphibians and reptiles 1st insects appear 1st flowering land plants (vascular) 250 million- PERMIAN EXTINCTION (95% extinct) and Pangaea forms (very dry, arid LARGE land mass)