Evolution of Vertebrates

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Evolution of Vertebrates

• Chapter 19

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Chordate Characteristics

• Dorsal, hollow nerve cords
• Notocord between GI tract and nerve cord
• Pharyngeal slits
• Post-anal tail

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Phylum Chordata

• Subphylum Cephalochordata

• Subphylum Urochordata

• Tunicates or Sea squirts
• Substrate causes metamorphosis
• Larva all 4 characteristics motile
• Adult slits only sessile
• Mucus aids filter feeding

• Lancets
• All 4 characteristics present
• Swollen tip of nerve cord
• Mucus for filter feeding
• Shows segmentation

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Development of Vertebrates
Emphasizes (in blue) characteristics of
vertebrate evolution Should refer back to with
each Class
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Class Agnatha (Jawless fish) Craniates, no
jaws, and notochord as main support

• Hagfishes

• Lampreys

• Weak vision, developed touch and smell (habitat)
• Enter prey through openings or create holes
• Can knot body or secrete slime

• Beginnings of vertebrae
• Larvae are suspension feeders that live in stream
  sediment
• Fish parasites
• Problematic in Great Lakes from St. Lawrence
  Seaway

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Class Chondricthyes (Cartilaginous
fishes)Craniates, jaws, and cartilage vertebrae
as main support

• Lateral line system to detect changes in water
  pressure and vibrations
• No operculum or swim bladder
• Clades
• Sharks
• Most are predators with powerful jaws (largest
  are filter feeders)
• Detect prey muscle movement through
  electrosensors on their head
• Sharp vision, keen smell, and streamlined bodies
• Stingrays and skates
• Suspension feeders
• Dorsoventrally flattened with eyes on top of head
• Barbed tails with venom glands (not skates)

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Class Osteichthyes (Bony fishes) Craniates,
jaws, and bony skeleton as main support

• Calcium phosphate mineralized cartilage
• Flattened scales covered in mucus reduces drag
• Operculum , protective flap covering the gills
• Can breathe without swimming, contrast to most
  sharks
• Swim bladder keeps them afloat
• Two dorsal fins, paired pectoral and pelvic fins
  (one bone)
• Clades
• Ray-finned fishes
• Lobe-finned fishes
• Coelacanth, lungfishes, and tetrapods

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Evolution of Tetrapods

• Lobe fins seem homologous to limbs
• Digits to create ground force
• Early development of lung-like structures
• Sense organs from water to land
• Fossils show fused girdles and head/neck
  separation
• Fish with necks

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Class AmphibiaTetrapods with 2 pairs of limbs

• Damp habitats so skin stays moist
• Skin has poison glands and coloration for defense
• Distribution limited by vulnerability to
  dehydration
• Ectothermic metabolism doesnt make heat must
  absorb
• Clades
• Salamanders and newts
• Walk side to side
• Caecilians
• legless
• Frogs
• Most adult life on land, but lay eggs in water
• Metamorphosis from tadpole (fish characteristics)
  to adult frog

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Class ReptiliaTetrapods with terrestrial egg
(amniotes)

• Eggs develop in fluid-filled amniotic sacs
  protected by a leathery shell
• Skin with scales and waterproofed by keratin
• Rib cage helps ventilate lungs
• Ectothermic
• Small dinosaurs may have been endothermic, using
  metabolism
• Clades
• Turtles and tortoises
• Shell and vertebrae are fused
• Lizards and snakes
• Snakes likely lost legs due to burrowing nature
  can detach jaws
• Lizards can detach tail, moveable eyelids, and
  external ear openings
• Crocodilians
• Most time in water with nostrils out
• Advanced behavior resembles birds and mammals

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Class AvesFeathered reptiles adapted to flight

• Lightened body structure
• No teeth, tail with few vertebrae, feather shafts
  hollow, and honeycombed bones
• Feathers of keratin provide lift and
  maneuverability
• Wings resemble air foils with large breast
  muscles
• Basis for classification
• Courtship and insulation role too
• High metabolism energy for flight and
  endothermic
• Highly efficient circulatory system, lungs, and
  vision
• Complex behavior, both sexes incubate hard
  shelled eggs and feed

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Class Mammalia

• Hair (keratin) and mammary glands
• Hair to insulate and increase size (goose bumps)
• Milk to nurture young
• Efficient respiratory and circulatory systems for
  high metabolism
• Endothermic
• Large brain and long parental care
• Differentiation of teeth for variety of foods
• One evolution from reptiles (current view)
• 3 lineages
• Offspring are hatched or birthed (loss of the
  egg)

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Monotremes

• Egg-laying mammals
• No nipples, milk sucked from glands on belly
• Only in Australia and New Guinea
• 2 existing members
• Duck-billed platypus (1)
• Spiny anteaters (4)

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Marsupials

• Higher metabolic rates and nipples
• Birth live young
• Complete development while nursing in external
  pouch
• No direct yolk sac/amnion connection
• Most live in Australia and New Zealand
• Opossums only ones in North America

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Eutherians (Placental Animals)

• Longer gestation fully developed live young
• Nurtured by a placenta
• Placenta nurtures by nutrient diffusion between
  mothers and embryos blood
• Many resemble marsupials ? convergent evolution

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Order Primate Phylogeny
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Order Primates

• Limber joints, 5 digits, flexible thumb and big
  toe
• Aids grasping and manipulation behaviors
• Adapted for arboreal (tree-dwelling) life
• Flat nails, not claws
• Reduced olfaction, increased vision
• Smaller noses, but larger forward facing eyes
• Smaller litter size, longer gestation, increased
  maternal care
• Fewer specialized teeth
• 2 incisors, 1 canine, 3 premolars, and 3 molars
  in each quadrant
• 2 taxonomic arrangements (generally)

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Prosimians

• Lemurs
• Only in Madagascar
• Primarily nocturnal
• Most social
• Lorises
• Africa and southern Asia
• All nocturnal
• Tarsiers
• Specialized for vertical climbing and leaping
• Southeast Asia and Indonesia
• Diet is almost completely animal matter

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Anthropoids

• Fully opposable thumb
• Monkeys
• Active during the day and live in social bands
• Fore- and hindlimbs about equal length
• New world
• Central and South America
• Nostrils wide open and far apart
• Long prehensile tail
• E.g spider monkeys and tamarins
• Old world
• Africa and Asia
• Lack prehensile tail
• Nostrils open downward
• E.g macaque, baboons, and rhesus
• Hominoids (Apes)

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Hominoids (Apes)

• Lack tails
• Long arms and short legs
• Mainly vegetarians
• Humans are omnivorous, eating plants and animals
• More flexible
• Larger brain relative to body size
• High degree of social organization
• 5 divisions

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Hominoid (Ape) Divisions

• Gibbons
• 9 species, all in Southeast Asia
• Only entirely arboreal apes
• Smallest, lightest and most acrobatic
• Monogamous for life
• Orangutan
• Solitary species in rain forests of Sumatra and
  Borneo
• Largest arboreal mammal, occasionally move on
  ground
• Gorillas
• Largest ape, found only in African rainforests
• Live in groups of up to 20
• Stand upright, walk on 4 legs with knuckles on
  the ground

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Hominoid (Ape) Divisions (cont.)

• Chimpanzees (and bonoboos)
• Knuckle walkers
• Tropical Africa
• Behavior closely mirrors humans
• Make simple tools
• Respond to mirrors
• Can learn human sign language
• Humans
• Bipedal, larger brain, capable of language,
  thought, and complex tools

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Vertebrate Diversity Review
List characteristics responsible for each branch
point (a-i)