Chordates

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Chordates
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Characteristics common to ALL chordates

• Dorsal nerve cord
• Pharyngeal slits
• Notochord
• Tail

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Dorsal nerve cord
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Pharyngeal Slits

• The wall of the pharynx is perforated by up to
  200 vertical slits, which are separated by
  stiffening rods.

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Jawless to Jaw
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Used to collect food in an aquatic environment
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Notochord

• a flexible, rod-shaped body found in embryos of
  all chordates

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• In lower vertebrates, it persists throughout life
  as the main axial support of the body, while in
  higher vertebrates it is replaced by the
  vertebral column.

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Tail
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Some animals lose tail during development
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Nonvertebrate chordates and Vertebrates

• Nonvertebrate chordates have a notochord
  (analogous to spinal chord) but lack a bony
  covering- the vertebrae
• Vertebrates have a spinal chord protected by bones

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Principle Chordate Features
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The Nonvertebrate Chordates

• Tunicates (sea squirts)
• exhibit neither a major body cavity nor visible
  segmentation
• tadpole larva clearly exhibits all basic
  characteristics of a chordate
• adults exist as sessile filter-feeders

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Tunicates
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The Nonvertebrate Chordates

• Lancelets
• scaleless, fishlike marine chordates
• notochord runs entire length of dorsal nerve cord
• feed on microscopic plankton using
  cilia-generated current

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Characteristics of Vertebrates

• Vertebral column
• Endoskeleton
• Distinct, well-differentiated head with cranium
• Closed circulatory system with chambered heart
• RBCs with hemoglobin

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Overview of the Evolution of Vertebrates

• Main CLASSES
• Fishes cartilaginous and bony
• Amphibia - amphibians
• Reptilia - reptiles
• Aves - birds
• Mammalia - mammals

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Fishes

• Over half of all vertebrates are fishes.
• Characteristics (generally)
• jaws and paired appendages (except lampreys and
  hagfish)
• scales
• fins
• gills
• single-loop blood circulation
• Heart with 2 chambers (1 atrium, 1 ventricle)
• Lateral line system

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History of the Fishes

• Rise of active swimmers
• Sharks and bony fishes replaced primitive fishes
  due to a superior swimming design.
• caudal (tail) fin
• dorsal (stabilizing) fins
• pectoral (shoulder - elevator) fins
• pelvic (hip- elevator) fins

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Hagfish
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Lamprey
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History of the Fishes

• Sharks become top predators
• Jaws with multiple rows of teeth
• Paired pectoral and pelvic fins
• Buoyancy from storing oil
• extremely advanced reproduction
• shark eggs fertilized internally
• Most give birth to live young

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Hammerhead Shark
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Elephant Fish
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Whale Shark
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Tooth from Megalodon (left), and Great White
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History of the Fishes

• Bony fishes dominate the water
• Skeleton composed of bone
• Swim bladder for bouyancy
• Gills protected by operculum
• highly mobile fins, thin scales, and completely
  symmetrical tails
• Most have external fertilization and external
  development

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Angler Fish
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Deep Sea Angler Fish
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Flounder
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Electric Eel
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Sea horse and Sea dragon
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Another Sea dragon
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Mola mola or Ocean sunfish
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Coelacanth
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Coelacanth fossils
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Living Coelacanth
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Shark Dissection
Following is a series of video clips of
dissection of various shark species. This will
give you some idea of what you will encounter
with our shark lab
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Lobe-Finned Fish and Primitive Amphibians
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Amphibians

• Live on both land and in water (double life)
• Characteristics
• legs
• cutaneous respiration, lungs, gills
• Heart with 3 chambers (double loop circulation)
• Pulmonary
• Systemic
• External fertilization and development in nearly
  all

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History of the Amphibians

• Adaptations for the invasion of land
• legs to support bodys weight
• lung to extract oxygen from the air
• redesigned heart to drive new respiratory system
• reproduction in water to prevent egg desiccation
• system to prevent body desiccation

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History of the Amphibians

• Amphibians today
• Anura - amphibians without tails
• most live in or near water, and return to water
  to reproduce
• eggs fertilized externally and hatch into
  tadpoles
• metamorphosis

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Poison dart frogs
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Proboscis frog
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African goliath frog
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Jabba the Frog
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Flying Frog
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Chinese fire-bellied toad (most venomous)
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History of the Amphibians

• Urodela (Caudata) - salamanders
• have elongated bodies, long tails, and sooth,
  moist skin
• fertilization is usually external

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Worlds largest salamander
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Spotted salamander
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Rodent surprise for lunch!
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History of the Amphibians

• Apoda
• caecilians - highly specialized group of tropical
  burrowing amphibians
• legless, but have jaws and teeth
• internal fertilization

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Caecilian
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Reptiles

• Characteristics
• amniotic egg
• chorion - outermost membrane
• amnion - encases embryo
• yolk sac - surrounds yolk (food)
• allantois - surrounds waste cavity
• dry skin with scales
• Internal fertilization usually external
  development

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Baby komodo dragon
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allantois
airspace
albumen
eggshell
amnion
embryo
chorion
Yolk sac
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Rise and Fall of Dominant Reptiles

• Dinosaurs learning to run
• body located directly over legs
• increased speed and agility

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Apatosaurus
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Triceratops
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Diplodocus
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Stegosaurus
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Velociraptor
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Another reconstruction of Velociraptor
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Some pterosaurs were the size of small airplanes
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Plesiosaurs were aquatic
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Japanese fisherman caught this creature in 1977
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Todays Reptiles

• Of the 16 orders of reptiles that have existed,
  only 4 survive
• turtles
• lizards and snakes
• tuataras
• crocodiles

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Rise and Fall of Dominant Reptiles

• Other important characteristics
• internal fertilization
• improved circulatory system
• ectothermic - heat obtained from external sources
• endothermic - generate own heat

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Gaping is a means of cooling the blood
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Living Reptiles

• Order Chelonia turtles and tortoises
• differ from other reptiles because their bodies
  are encased within a protective shell

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Some tortoises have lived to 150 years
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Green sea turtle
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Pacific leatherback sea turtle
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Rise and Fall of Dominant Reptiles

• Order Rhynchocephalia tuatara
• lizardlike animals about half a meter long
• contain parietal eye
• only found on island off New Zealand coast

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Rise and Fall of Dominant Reptiles

• Order Squamata lizards and snakes
• three suborders
• Sauria - lizards
• Amphisbaenia - worm lizards
• Serpentes - snakes
• paired copulatory organ in males
• lower jaw not joined directly to skull

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The chameleon is a lizard
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Jacksons chameleon
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Gecko
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Gila monster (venomous)
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Skinks are sometimes called worm lizards
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Blue-tongued skink
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Worlds smallest skink
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Rainbow boa constrictor
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Scarlet king snake
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Coral snake
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King or Coral?
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Copperhead
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Sidewinder rattlesnake
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Rattlesnake victim
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Rise and Fall of Dominant Reptiles

• Order Crocodilia crocodiles and alligators
• remained relatively unchanged
• only two species of alligators
• southern US and China
• resemble birds more than other living reptiles
  (care for young and four-chambered heart)

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Nile crocodile
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Caimans live in South America
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Gharial
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Birds

• Class Aves contains 28 orders containing 166
  families and about 8,600 species.
• key characteristics
• feathers
• modified reptilian scales ?
• flight skeleton
• thin, hollow bones

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History of the Birds

• Archaeopteryx (similar to modern Hoatzin)
• Aves listed as separate class because of key
  evolutionary novelties of feathers, light bones,
  and super-efficient lungs

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History of the Birds

• Birds today
• adaptations for flight energy demands
• efficient respiration
• efficient circulation
• Endothermy

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The Great Nest measures 9.5 ft. across, 20 ft.
deep, and weighs an estimated 2 tons.
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Mammals

• Key mammalian characteristics
• hair
• heat loss
• camouflage
• sensory structures
• defense weapon
• mammary glands
• about 50 of energy in milk comes from fat

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A mother tiger, like other mammals, will not have
to leave her young in order to find food for them
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Key Mammalian Characteristics

• endothermy
• crucial adaptation that allowed activity at any
  time of the day to colonize severe environments
• placenta
• specialized organ allowing food, water, and
  oxygen to pass from mother to child
• teeth
• heterodont dentition (different teeth for
  different functions)

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Neither of these animals is a fierce carnivore,
despite the appearance of their teeth
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Key Mammalian Characteristics

• digestion of plants
• cellulose major source of food for herbivores
• mammals do not have necessary digestive enzymes
  to break apart cellulose
• some have evolved four-chambered stomachs
• some contain mutualistic bacteria in a cecum

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Giraffes, like cows, possess a chambered stomach.
All ruminants chew cuds
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Although horses and zebras are herbivorous like
giraffes, they do not have a rumen. Instead, they
possess a cecum.
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Key Mammalian Characteristics

• hooves and horns
• hooves specialized pads of keratin
• horns composed of core of bone surrounded by
  keratin sheath
• flight
• bats have wing of leathery membrane of skin
  stretched over the bones of four fingers
• second largest order of mammals
• echolocation

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History of the Mammals

• Orders of mammals
• monotremes egg-laying mammals
• lay shelled eggs
• marsupials pouched mammals
• finish development in external pouch
• placental mammals
• placenta nourishes embryo throughout entire
  development
• Gestation length related to size

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echidna
The echidna is also known as the spiny anteater
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koala
Koala young stay with the mother for an extended
period of time, hitching a ride on moms back
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Theyre even cute when theyre asleep
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Tasmanian devil
There really is a Tasmanian devil
Tasmanian Devil
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kangaroo
There are many species of kangaroo. In addition
to the red (shown here), there is even a species
that climbs trees
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You didnt believe me, did you?
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The capybara is the worlds largest rodent.
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sloth
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Star nosed mole
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Manatee?

• Manatees are very docile creatures

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Notice the teeth on this orca
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Beluga whale
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The blue whale can measure over 90 ft. long and
weigh over 200 tons
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Evolution Among Primates

• Primates
• two distinct features allowed them to succeed in
  arboreal environment
• grasping fingers and toes
• binocular vision
• Prosimians (lemurs and tarsiers)
• Very smell oriented
• Usually have long tails

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The tamarin is a prosimian
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The aye-aye is a most unusual prosimian
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Anthropoids

• Higher primates - includes apes, monkeys, and
  humans
• The term Anthropoid means Like us
• Direct descendents
• New World monkeys (South America)
• Old World monkeys (Africa)

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mandrill
The mandrill is an anthropoid monkey related to
the baboon
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New world monkeys like this spider monkey have
prehensile or grasping tails. The Old World
monkeys lack the ability to grasp with the tail
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gorilla
The silverback is a mature male gorilla who
fears nothing
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orang
The orangutan is found only on Borneo and Sumatra
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gibbon
Gibbons are extremely athletic apes found in
Southeast Asia. Like all apes, gibbons are
tail-less
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Chimpanzees have very complex social groups,
interact often with one another, and are very
devoted parents
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Chimps have often been seen in the wild using
tools. What do you suppose this guy is doing with
the stick?
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• Human evolution is very controversial
• Fossils are extremely rare and difficult to
  interpret
• Dating of fossils is also suspect
• H. sapiens is the only surviving hominid.
• The best fossils are between 90,000 and 100,000
  years old.
• Cro-Magnons replaced Neanderthals about 40,000
  years ago.
• Humans of modern appearance eventually spread
  across Siberia to North America about 13,000
  years ago.

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