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Chordates, Craniates and Vertebrates

Chordates, Craniates and Vertebrates. Echinoderms Hemichordates Chordates. Deuterostomes. Why??. Fundamentally different type of development Protostomes (first mouth) = annelids arthropods, molluscs spiral cleavage one opening different mesoderm formation

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Chordates, Craniates and Vertebrates

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  1. Chordates, Craniates and Vertebrates

  2. Echinoderms Hemichordates Chordates Deuterostomes Why??

  3. Fundamentally different type of development • Protostomes (first mouth) = annelids arthropods, molluscs • spiral cleavage • one opening • different mesoderm formation • Deuterostome (second mouth)

  4. Echinoderms Hemichordates Chordates Deuterostomes

  5. Echinoderms starfish, brittle stars, sea lillies

  6. Hemichordates acorn worms, pterobranchs

  7. Chordates

  8. Tunicates Cephalocordates Craniates Chordates Why? because all embryos have a notochord

  9. Tunicates sea squirts, colonial or single Pharyngeal slits Has a heart & circulatory system, ganglion = brain, hermaphrodites, sexual or asexual

  10. Endostyle secretes mucus. Nerves from ganglion extend into siphon, muscle cells & visceral organs

  11. Notochord found in embryos of all chordates

  12. Cephalochordates e.g. amphioxus 3-5cm long, pointed at both ends, short post-anal tail, no head, burrows in sand – either way round

  13. notochord

  14. Feeds buried in sand with its anterior end out, filter feeder. Gills for feeding NOT respiration.

  15. Sophisticated circulatory system, much like a craniate, no true capillaries , no heart, blood propelled by contraction esp of branchial bulbs, no haemoglobin O2 dissolves

  16. Tactile receptor, chemoreceptors, photoreceptors (in floor of neural tube, responds to light from above, pigment spot at anterior end), sensory nerves from skin. Sexes separate

  17. 5 characteristics of chordates (tunicates, cephalochordates, craniates): • pharyngeal slits, cilia for filter feeding (later became respiratory) • endostyle (certain cells in endostyle bind proteins with iodine – thyroid gland?) • notochord (resists compression for locomotion) • dorsal neural tube (arthropod nerve cord is ventral) • post-anal tail in larva

  18. Human embryos!!

  19. Tunicates Cephalocordates Craniates Chordates HEAD !!!

  20. Head • very distinct from trunk and tail • mouth, gill slits • concentration of sense organs (nose, eyes, ears), swollen nerve cord = brain • brain protected in cranium

  21. Most characteristics associated with increased size and high levels of activity Vertebral column for locomotion Gills for respiration Jaws for catching & feeding Heart for circulation + haemoglobin Liver, pancreas Endocrine organs

  22. Craniate

  23. Hagfish (Myxniformes) Slime glands Braincase Brain Nose Eyes Liver Heart Renal tubules Gills NO bone, vertebrae, jaws, paired appendages

  24. Vertebrates Vertebrae Semicircular canals Fin muscles Lampreys (Pteromyzontiformes) NO jaws (agnathous)

  25. How did jaws come about?

  26. Cartilaginous fishes = Chondrichthyes Sharks, skates, rays, chimaeras (800 living species) Unique scales=placoid, internal fertilisation, oviparous, ovoviviparous or viviparous (uterine cannibalism) No lungs or swim bladder

  27. Holocephali = chimaeras

  28. Bony fish = Osteichthyes • 49,000 living species • Lungs or swim bladder, bony fin rays with jointed appearance. • Actinopterygii – single dorsal fin, majority are Teleosts • Sarcopterygii – muscular fins • Coelacanth • Lungfish • look like they are • walking on the bottom • can breath with lungs

  29. Tetrapods Decreased resources in sea, untapped resources on land, inverts, plants etc Muscular limbs Dactylous limbs – 5 to 8 digits Vertebral column strengthened for locomotion New sense organs Water conserving Are coelacanths or lung fishes more closely related to tetrapods?

  30. Amphibians • Caecilians • Urodeles • Anura • Hands reduced to 4 digits • Metamorphosis – bimodal • Ear, eardrum

  31. Amniotes Key to fully terrestrial life (no need for water) – amnion Dry keratinized outer skin Distinctive ankle bone Turtles Debate about where they fit V. distinctive, carapace, no teeth, keratinised beak

  32. Tuatara & squamates 6000 lizards, snakes, iguanas Many elongated trunks and lost legs. Squamates have special copulatory organ = hemipenis Archosauromorphs (pterosaurs, dinosaurs) Crocodilians T. Rex bipedalism appears

  33. Aves • Archeopterix – teeth + feathers • Ostriches – mostly flightless and large • Modern birds – 9000 species • feathers • flight + all its adaptations

  34. Mammals • special ear bones, cochlea • hair, independent evolution of endothermy • special teeth • uterus, mammary glands Early mammals like the tenrec, small insectivorous, active at night, excellent sensory system

  35. Montremes – single opening of u-g & fecal, electrosensory system in bill, lay eggs. Echidna, platypus Marsupials – short intrauterine life then enter marsupium. Opossums, marsupial cats, bandicoots, kangaroos Eutheria – placental mammals. From armadillos through whales to primates.

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