Vertebrates

• Chordate


  • notochord: cartilage rod, skeletal support, reduced in adult stages
  • nerve cord: ectodermal cells, develops into spinal cord
  • pharyngeal slits/clefts: groves or opening in pharynx- evidence of segmentation
  • Post-anal tail
• chordate diagram


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• What phyla is a good example of chordate bosy pla?

  Cephalochordates (lancelets)
• what are Urochordata?


  tunicates- sessile, marine, filter feeders

  • colonise
• give an example and describe a tunicate colony?

  pyrosomes- pelagic tunicate colonies

  • use slits as feeding net
  • passivly float
• What did Ernest Haeckel‘s recapitulation theory discuss?

  Ontogeny recapitulates phylogeny > biological development parallels and summaries species evolutionary development
• Lancelets


  • small
  • Fish-like
  • Notochord throughout life
  • In sand
  • Filter prey in slits
  • Small brain
• Urochordates


  tunicates

  • 1-60cm
  • plankton
  • sessile adults
  • tadpole like larvae with chordate traits
  • invasive
  • closely related to vertebrates
• Vertebrates


  Rigid internal skeleton

  • two pairs of appendages
  • Anterior skull and large brain
  • Large coelom
  • Ventral heart
• jawless fish


  myxini (hagfish) + petromyzontida (Lamprey)

  • 2+ clusters of hox genes
  • Neural crest
• why are myxini (hagfish) unlike other vertebrates?

  • low pressure circularatory system
  • partial cranium, no cerebrum or cerebellum
  • cartillage skeleton
  • reduced vertebrae
• What are the jawed fish?

  Gnathostomes: vertebrae with jaws

  Placoderm > early, heavily armoured evolved sleek body and fins > extinct

  Acanthodians > spiny fins > extinct

  Chondrichthyes > living forms of jawed fish
• modern Gnathostomes (Chondrichthyans)


  -duplication of hox genes > increased morphology

  -enlarged forebrain

  • sharks, rays
  • skeleton mainly cartilage
• Chondrichthyan reproduction


  males > claspers 9semen channelers)

  females > eggs fertilised internally

  • oviparous > hatch outside
  • ovoviviparous > inside nourished by egg yolk
  • viviparous> inside nourished through yolk sac placenta by mothers blood
• what group fo the ray-finned fish (actinopterygii) belong to?

  Osteichthyes group

  • gills protected by operculum
  • bouyency control by swim bladder
• ray finned fish key features

  • calcified endoskeleton
  • thin bones
  • 1 flap operculum
  • scales cover skin
  • swim bladder > achieves neutral buoyancy
• lobe fin fish group

  • actinistia
  • dipnoi
• actinistia key features


  large fish

  muscles in limbs out of body >homologous to tetrapod limbs

  thought extinct until 20th centuary
• dipnoi (lungfish)

  monophyletic

  • powerful jaws
  • thick central lobe with bone and muscle
  • gulp air > allows survival in stagnant water
  • aestivation
• Aestivation


  state of dormancy in dummer (during low water levels)
• Evolutions of tetrapods


  Panderichthys- digit and radial bones

  Tktaalik- fish-apod

  - eyes on top of skull

  - neck, ribs, flat skull

  acanthostega

  -four limbs double digits gills and lungs
• Amphibians


  Eggs > metamorphosis > terrestrial

  Three orders

  • Apoda (caecilians, worm)
  • Urodela (salamanders +newts)
  • Anura (frogs and toads)
• Apoda (caecilians)


  moist forest soil, burrowers

  -viviparous (matrophagy)
• Urodela - salamanders and newts

  tail

  mostly cooler northe temperate regions
• Anura - 


  frogs and toads
• Amniotes


  amniotic egg

  • reptiles
  • birds
  • mammals
• amniotic egg


  amnion- surrounds embryo

  chorion- encloses embryo, yolk sac and allantois

  yolk sac- yolk

  Allantois- waste products (umbilical in humans)
• reptiles


  scales- keratin

  internal fertilisation- prior to laying egg

  concentrated urine

  paraphyletic group
• 4 main amniotic groups


  diapsids- common ancestor of reptiles and birds

  lepidosaurs- tuataras, squamates (lizards and snakes)

  archosaurs- turtles, crocodiles, dinosaurs and birds

  mammals- completely separate
• lepidosaurs


  horny scales, shed outer layer, lung ventilation, chambered heart, reduction of limbs
• archosaurs


  Chelonins- turtles etc > boxed shell

  Crocodililians- carnivourous

  Dinosaurs- Mesozoic era

  Saurischia- carnivorous or long-necked herbivore

  Ornthischia- herbivorous
• bird flight adaptations


  • hollow bones
  • no bladdar
  • mall gonad
  • one ovary
  • loss of teeth
  • feathers and wings > Kerratin > evolved before flight suggest alternating role
• Paraphyletic


  Some descendants of s a single ancestor
• polyphyletic 


  most common ancestor is not a part of the group
• monophyletic


  all descendants of a single ancestor
• What are the three lineages of mammals

  Monotremes

  Marsupials

  Eutherians- species rich
• monotremes


  • Lay eggs
  • Platypus and echinda
• marsupials


  • opossums, kangaroos, koalas
  • embryos devolp in uterus > development completed in mother pouch (marsupium)
• Eutherians


  • Longer gestation
  • Complex placenta
  • Lots of convergent evolution with marsupials
• primates


  • complex behaviour
  • opposable thumbs
  • hominoids> apes