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26.2 Chordate Evolution

26.2 Chordate Evolution . Embryo evidence suggests earliest chordates were related to echinoderms!. Pikaia - early chordate - has notochord, no bones (also called M ylokunmingia ). Cartilage - strong connective tissue more flexible than bone (came before bone)

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26.2 Chordate Evolution

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  1. 26.2 Chordate Evolution

  2. Embryo evidence suggests earliest chordates were related to echinoderms! Pikaia - early chordate - has notochord, no bones (also called Mylokunmingia)

  3. Cartilage - strong connective tissue more flexible than bone (came before bone) • Mainly made of collagen protein

  4. Modern Chordates - 6 groups - 1 invertebrate group - 5 vertebrate groups - fish, amphibians, reptiles, birds, mammals

  5. 1) Invertebrate chordates - tunicates and lancelets

  6. Lancelet

  7. 2) Jawless fish - had cartilage skeletons • Filter feeders • Related to modern hagfish, lamprey HEMICYCLASPIS

  8. Lamprey Eel

  9. Some species of Lamprey are parasitic, some are filter feeders

  10. Filter feeding - filters out small animals (like krill) BALEEN

  11. 3) Fishes with Jaws - sharks - allowed them to bite and chew large plants and animals

  12. The move from sea to land required: a) Four limbs - tetrapod Tiktaalik

  13. b) Gills to lungs

  14. c) Amniotic egg - egg with protective layer to withstand terrestrial climate (shell, membrane)

  15. Endothermy - (within heat) “warm blooded” - mammals and birds - can alter metabolism to maintain internal temp.

  16. Use the text to answer page 412 in the workbook!!

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