BIO 203...Ch. 34

BIO 203...Ch. 34 - Allison Schwab BIO 203 Chapter 34...

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Allison Schwab BIO 203 Chapter 34 Vertebrates 1) 540 million years ago animals inhabited the oceans a) Gave rise to vertebrates i) Contain a series of bones that make up the backbone 2) 360 million years ago the evolution of legs and feet allowed species to move onto land 3) Chordates: bilaterally symmetrical animals that belong in the clade Deuterostoma. a) Derived Characteristics i) Notochord (1) longitudinal, flexible rod located between the digestive tube and the nerve chord (2) Provides support, composed of fluid-filled cells and fibrous tissue. ii) Dorsal, hollow nerve cord (1) Tube of ectoderm dorsal to notochord (2) Develops into central nerves system iii) Pharyngeal Slits (1) Grooves along the side of the Pharynx that open into slits (2) Allow water to exit the body without going through the entire digestive track (3) Modified for gas exchange; gills iv) Post-anal tail (1) Contains skeletal elements and muscle (2) Propelling force in aquatic animals b) Tunicates i) Deepest linage of Chordates ii) Looks like chordates during larva stage iii) Once it lands on a substrate, it goes through radicalmetamorphosis (1) Tail and notochord resorbed, nervous system degenerates, organs rotate 90 degrees c) Lancelets i) Bladelike shape ii) Feed on plankton iii) Retain key chordate shape iv) Adult lancelets burrow into the sand 4) Craniates: Chordates with a head. They have a brain, skull, and sensory organs (eyes). a) Derived Characteristics i) 2 clusters of Hox genes ii) Neural crest (1) Collection of cells near the dorsal margins of the closing neural tube in an embryo
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(2) Give rise to teeth, some bones and cartilage of skull, dermis layer of skin (on face), some neurons, and sensory capsules iii) Heart with at least 2 chambers, red blood cells, and hemoglobin b) Origin i) Cambrian explosion: 530 million years ago
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BIO 203...Ch. 34 - Allison Schwab BIO 203 Chapter 34...

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