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The Chordate Phylum

Chordate phylum: 6 vertebrate and 2 invertebrate classes, all having a similar set of 25,000 genes. The Chordate Phylum. Chordates: 6 vertebrate classes. Class: Birds. Hummingbird. Class: Reptiles. Bardick snake. Class: Birds. Hornbill. Class: Mammals. Mouse. Class: Mammals. Mandrill.

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The Chordate Phylum

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  1. Chordate phylum: 6 vertebrate and 2 invertebrate classes, all having a similar set of 25,000 genes The Chordate Phylum

  2. Chordates: 6 vertebrate classes Class: Birds. Hummingbird Class: Reptiles. Bardick snake Class: Birds. Hornbill Class: Mammals. Mouse Class: Mammals. Mandrill Class: Mammals. Monotremes; Echidna

  3. Phylum: Chordates. 6 vertebrate classes Class: Cartilaginous fish. Ratfish, Chimera Class: Jawless fish. Hagfish Class: Bony fish. Teleost. Anemone fish Class: Amphibia. Xenopus tadpoles Class: Bony fish. Coelacanth

  4. Invertebrate chordates: 2 classes posterior anterior Phylum: Chordates. Class: Cephalochordates Phylum: Chordates. Class: Urochordates; Ascidians Nearest phyla to chordates Phylum: Echinoderms. Starfish Phylum: Hemichordates; Class: Enteropneust

  5. Chordates and Arthropods are descended from a pre-Cambrian bilateral ancestor; as are the other 24 bilateral phyla

  6. Xenopus laevis, the South African three clawed frog Oocytes surgically removed

  7. Stages of Xenopus development Oocytes in the ovary. Note blood vessels Unfertilized eggs, in jelly coats Grey crescent Sperm entry point 4-cell stage, 2.5 hr Fertilized egg, 30 min.

  8. Stages of Xenopus development Animal pole view Blastopore almost closed Late blastula, 9 hr. About 8000 cells Late gastrula, 16 hr Neural folds Late neurula, 30 hr Tadpoles, 2 weeks old, feeding

  9. Phylotypic stage(pharylgula/tailbud stage): first embryonic stage to possess the main chordate traits, and an “adult”map of >200 gene expression domains covering the 3 germ layers(all preceding organs and cell types)

  10. Gene expression domains at the midbrain-hindbrain boundary (zebrafish example)

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