The Vertebrate Genealogy

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The Vertebrate Genealogy

• Chapter 30

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What is a chordate?

• There are 4 anatomical structures that appear
  during some point during the animals lifetime
• 1. Notochord long flexible tube between the
• gut and the nerve cord
• - becomes gelatinous material
• between vertebrae in humans
• 2. Dorsal, hollow nerve cord becomes CNS
• 3. Pharyngeal slits
• 4. Muscular postanal tail most chordates
• have a tail that extends beyond the anus

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What is a chordate?
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Survey of Vertebrate Classes

• Fishes Agnatha, Chondrichthyes,
  Osteichthyes
• Tetrapods Amphibia, Reptilia, Aves,
  Mammalia
• Amniotes Reptilia, Aves, Mammalia
• Have a shelled water-retaining egg

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Class Agnatha

• Sample organisms
• Hagfishes, lampreys
• Jawless vertebrates
• Feed by sucking blood after clamping onto prey or
  by scavenging
• Do not have paired appendages

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Class Chondrichthyes

• Sample organisms sharks and rays
• Cartilaginous fishes have relatively flexible
  skeletons made of cartilage rather than bone
• Most sharks are carnivorous and have acute senses

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Class Osteichthyes

• Bony fishes
• Have hard skeletons (due to ossification)
• Sample organisms perch, trout
• Breathe by drawing water over 4-5 pairs of gills
  covered by operculum (protective flap)
• Most bony fishes are oviparous
• Females lays large numbers of eggs, fertilization
  occurs externally

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Class Osteichthyes
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Class Amphibia

• The first vertebrates (tetrapods) on land
• Amphibians must deposit their shell-less eggs in
  water
• Sample organisms frogs salamanders
• Amphibian two lives
• Tadpole larval stage
• Metamorphosis occurs
• Frog legs develop
• Salamanders have tails
• Frogs do not have tails

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The Amniotic Egg

• The amniotic egg is a reproductive adaptation
  that allowed terrestrial vertebrates to complete
  their life cycles on land
• The shell prevents the egg from drying out
• 4 layers of protection
• Amnion prevents dehydration, cushions shocks
• Yolk Sac stockpile of nutrients
• Allantois disposal sac for certain metabolic
  wastes
• Chorion gas exchange

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Class Reptilia

• Sample organisms lizards, snakes, turtles,
  crocodiles
• Reptiles have scales made of keratin that cover
  their skin
• Obtain oxygen with their lungs
• Fertilization occurs internally
• Most reptiles lay amniotic eggs on land
• Ectotherms body temperature fluctuates with the
  environment

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Class Aves

• Birds are tetrapods with feathers
• Their forelimbs are modified as wings
• Sample organisms owl, sparrow, penguin, eagles
• Lay amniotic eggs
• Endothermic regulate their own body temps.
• Anatomy adapted for flight
• Form function

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Class Mammalia

• Mammals have hair
• Endothermic
• Mammary glands that produce milk
• Most mammals are born, not hatched
• Three major groups
• Monotremes lay eggs
• platypuses, echidnas
• Marsupials complete development in a maternal
  pouch
• Kangaroos, koalas, opossums
• Placental mammals complete development within
  the uterus, joined to the mother by the placenta
• Sheep, bats, elephants, humans

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Paleoanthropology

• Paleoanthropology is the study of human origins
  and evolution
• Correcting misconceptions
• Lets first dispose of the myth that our
  ancestors were chimpanzees or any other modern
  apes. Chimpanzees and humans represent two
  divergent branches of the anthropoid tree that
  evolved from a common, less-specialized
  ancestor.

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Paleoanthropology

• 1974 Ethiopia
• Lucy is an Australopithecus skeleton
• 3.18 million years old
• Homo habilis
• 2.5 million years ago
• Enlargement of the human brain
• Homo erectus
• First hominid to migrate out of Africa into Asia
  and Europe
• Taller than H. habilis and a larger brain capacity

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Paleoanthropology

• 2 models of how Homo sapiens evolved

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To think about

• Of the many crises in the history of life, the
  impact of one species, Homo sapiens, is the
  latest and potentially the most devastating.
• - Neil Campbell, 4th ed.