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Prof. Stuart Bunt

Evolution of the Brain. Prof. Stuart Bunt. Humans are only one animal. Much of our knowledge of the development of the brain comes from study of other animals Caenorhabditis elegans for cell lineages and genetics Drosophila for genetics Xenopus laevis for vertebrate embryology

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Prof. Stuart Bunt

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  1. Evolution of the Brain Prof. Stuart Bunt

  2. Humans are only one animal Much of our knowledge of the development of the brain comes from study of other animals • Caenorhabditis elegans for cell lineages and genetics • Drosophila for genetics • Xenopus laevis for vertebrate embryology • Zebra fish for vertebrate lineages • Chick and quail for transplants/lineages • Mouse and rat for mammalian development • Fish and marsupials for regeneration of the CNS

  3. We need to know their taxonomic relationships • How closely related are their nervous systems? • What characteristics are derived? • What characteristics are convergent? • What pre-adaptations are required? • What restricts nervous system development in different phyla? • Only evolution can make sense of taxonomic relationships • Taxonomy is based on presumed evolution

  4. Nerve Nets Even primitive animals can have complex behaviour

  5. Hirudinea (Leeches) With the addition of a gut, cephalization and segmentation a segmental nerve pattern arises.

  6. Interneurons & Sensory Cells Added

  7. Segmentation Common in Invertebrates

  8. Invertebrate Embryology is Determinate Individual cells can be identified Cells have specific lineages Destroy cells, specific parts of the embryo are missing Vertebrates are regulative (otherwise in vitro fertilization would be impossible)

  9. Invertebrate embryology is variable and quite unlike that of vertebrates

  10. Cephalopods Have the most complex nervous systems

  11. Invertebrate nervous systems are ventralVertebrate nervous systems are dorsal Annelids Amphioxus

  12. Vertebrate Nervous Systems are Dorsal The inverted lobster!

  13. Hemichordates are a side issue?

  14. We most likely evolved from tunicates • Only echinoderms and vertebrates share caudal gastrulation • Tunicates are sessile filter feeders • Their larvae are mobile • Some salps are permanently mobile • Their tails have somites and a notocord • Add a basic neural tube and you end up with Amphioxus.

  15. All vertebrate embryos look very similar

  16. Primate evolution has been marked by an increase in cerebral volume by a rotation of the foramen magnum

  17. Are Humans “Different”? • Development of language needs many preadaptations? • Use of hands and tools precede brain development • Neanderthals had larger cranial capacity than Homo sapiens • When did consciousness evolve? • Is the brain more than just cells?

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