Vertebrate Evolution and Diversity

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Vertebrate Evolution and Diversity

• Chapter 34

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• Vertebrates belong to phylum Chordata.
• Includes 3 subphyla, vertebrates and 2 phyla of
  invertebrates, urochordates and cephalochordates.
  
• 4 characteristics notochord dorsal, hollow
  nerve cord pharyngeal slits and muscular,
  postanal tail.

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• Notochord, present in all chordate embryos -
  flexible rod between digestive tube and nerve
  cord.
• Dorsal, hollow nerve cord develops in vertebrate
  embryo from plate of ectoderm that rolls into
  tube dorsal to notochord - can develop into
  spinal cord.

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http//www-biol.paisley.ac.uk/courses/tatner/biome
dia/jpegs/hypchrdb.jpg
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• Pharyngeal gill slits connect pharynx, just
  posterior to mouth, to outside of animal.
• Most chordates have muscular tail extending
  posterior to anus.

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http//science.kennesaw.edu/biophys/biodiversity/a
nimalia/cephal.gif
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Tunicates

• Sessile marine animals that adhere to rocks,
  docks, and boats.
• Invertebrates - urochordates.
• Chordate characteristics are present as larva.
• Suspension-feeders.

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http//www.aboututila.com/Reviews/Charlie-Johnson/
Photos/Bluebell-Tunicates.jpg
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Lancets

• Cephalochordates - have chordate characteristics
  in adult.
• Suspension-feeders.

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Lancet
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Vertebrates

• Neural crest, pronounced cephalization, vertebral
  column, closed circulatory system - subphylum
  Vertebrata.
• Neural crests start of formation of cranium
  cephalization - collection of nervous tissue that
  forms brain.

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http//bio1151.nicerweb.com/doc/class/bio1151/Lock
ed/media/ch34/34_07NeuralCrest_L.jpg
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• Have appendicular skeleton, supporting 2 pairs of
  appendages (fins, legs, or arms).
• Can be made of either bone, cartilage, or both.

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http//sciencecity.oupchina.com.hk/biology/student
/glossary/img/appendicular_skeleton.jpg
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Jawless vertebrate

• 2 classes of jawless vertebrates still living
  Class Myxini (hagfish) and Class
  Cephalaspidomorphi (lampreys).
• Hagfish - skeletons made of cartilage making them
  flexible, but no backbone.

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Hagfish
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• Lampreys - parasites with cartilage skeletons.
• Lack backbone - have notochord.

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Jawed fish

• Jawed fish broken into 2 classes (extant).
• Chondrichthyes (cartilaginous fishes sharks,
  rays), Osteichthyes (bony fishes ray-finned
  fishes, lobe-finned fishes, lungfishes).

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http//palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgro
ups/Chondrichthyes/megalodon.jpg
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• Chondrichthyes - skeleton made of cartilage.
• Cartilaginous skeleton usually replaced by bone
  chondrichthyes - process prevented.
• Fertilize internally some lay eggs (oviparous),
  few give birth to live young (viviparous)

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• Osteichthyes - bony fish - endoskeleton made of
  bone.
• Bony fish have swim bladder not found in
  cartilaginous fish - helps control buoyancy of
  fish.
• Bony fish actually broken down into 3 groups
  ray-finned fishes, lobe-finned fishes,
  lungfishes.

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Ray-finned fishes
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Lobe-finned fish
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http//www.cartage.org.lb/en/themes/Sciences/Zoolo
gy/Biologicaldiverstity/AnimalsIII/coelacanth.jpg
Lungfish
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Tetrapods

• Tetrapods -land animals - walk on all fours -
  transition from water animals to land animals -
  amphibians.

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• Class Amphibia - amphibians - salamanders, frogs,
  caecilians (legless animals that burrow)
• Fertilization external - lay eggs.
• Most amphibians rely heavily on moist skin to
  carry out gas exchange with environment - still
  tied to water.
• Some adult frogs have lungs.

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Caecilian
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Amniotes

• Mammals, birds, reptiles, including turtles,
  lizards, snakes, crocodiles.
• Transition to land - adaptations were needed
  amniotic egg, waterproof skin, increasing use of
  rib cage to ventilate lungs.

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http//content.answers.com/main/content/wp/en-comm
ons/thumb/f/fc/250px-Tortoise-Hatchling.jpg
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• Amniotic eggs of most amniotes have shell that
  retains water - can be laid in dry place.
• Inside shell of amniotic egg - several
  extraembryonic membranes that function in gas
  exchange, waste storage, and transfer of stored
  nutrients to embryo.

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Reptiles

• Class Reptilia divided into 4 orders.
• Reptiles - several adaptations for terrestrial
  life not found in amphibians - leathery skin to
  prevent dehydration, lungs.
• Fertilization internal, eggs laid (amniotic eggs)

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http//www.dnr.state.wi.us/org/caer/ce/eek/critter
/reptile/images/turtleHatching.jpg
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• Reptiles - ectotherms - cannot maintain own
  internal temperature (cold-blooded).
• Turtles return to water to lay eggs have not
  evolved since 1st appearance.
• Lizards - most numerous reptiles.

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• Snakes - limbless reptiles - still have pelvic
  bones - evidence that they evolved from reptiles
  with legs.
• Crocodiles and alligators - largest living
  reptiles.
• Breathe through their nostrils that are pointed
  upward out of water.

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Birds

• Birds - class Aves - broken down into 28 orders
  (few flightless birds)
• Birds evolved to have hollow bones to allow for
  flight and feathers.
• Modern birds - toothless - grind food in muscular
  gizzard near stomach.

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• Large brains of birds (proportionately larger
  than reptiles or amphibians) support very complex
  behavior.
• Birds - endotherms - metabolism allows them to
  regulate internal temperature.

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Mammals

• Mammals - class Mammalia - identified by mammary
  glands.
• Most mammals give birth to live young after
  internal fertilization.
• Nutrition done via placenta.
• Most mammals capable of learning due to larger
  brains.

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• Monotremes - duck-billed platypus and echindas -
  lay eggs that have yolks to support embryo.
• Marsupials - born early in development crawl into
  pouch in mother to complete development.
• Eutherians - placental mammals.

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http//cache.eb.com/eb/image?id94548rendTypeId4
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Echinda
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http//marsupials.org/koalaalb.jpg
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Opposum
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http//www.ucmp.berkeley.edu/mammal/eutheria/rat.j
pg
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• Primates - most advanced of eutherians.
• Opposable thumb characteristic of most advanced
  primates.
• Divided into 2 groups prosimians (lemurs),
  anthropoids (apes, humans).

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http//www.dumondconservancy.org/dc2005/images/web
/troy20originals/lemur8.jpg
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http//www.dkimages.com/discover/previews/920/5504
8736.JPG
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• New World monkeys - arboreal (live in trees) -
  tails used for grasping.

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• Hominoid - great apes and humans collectively.
• Hominid - group closely related to humans.
• Human evolution included many adaptations -
  larger brains, ability to stand upright.

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http//www.nhc.ed.ac.uk/images/vertebrates/primate
s/HominoidSkulls.jpg
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