Compare and Contrast Why did scientist classify Pikaia as a chordate instead of as a worm

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1. Compare and Contrast Why did scientist classify
   Pikaia as a chordate instead of as a worm
2. Review What two aspects of evolutionary history
   does the cladogram of chordates show
3. Apply Concepts Recall what you learned about
   plant evolution in Ch 22. In what ways are
   chordate adaptations to life on land similar to
   plant adaptations. Based on the sequence of
   evolutionary change what was the first major
   adaptation of each

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Ch 26 Animal Evolution and Diversity

• 26.2 Chordate Evolution and History

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• Embryological studies suggest that the most
  ancient chordates were related to the ancestors
  of echinoderms.

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Earliest Chordates

• Pikaia
• Cambrian fossil
• First thought it was a worm but then determined
  that it had a notochord and paired muscles
  arranged in a series.

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• Cartilage
• Strong connective tissue that is softer and more
  flexible than bone.

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Nonvertebrate Chordates

• 550 million years ago
• Tunicates and lancelets
• Turnicates
• Adults look like sponges
• Larval forms have all the key chordate
  characteristics.

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Jawless Fishes

• 510 million years ago
• No true jaws or teeth, and their skeletons were
  made of cartilage.

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Jawless Fishes

• Lampreys and hagfishes both lack vertebrae and
  have notochords as adults
• Lampreys are filter feeders as larvae and
  parasites as adults
• Hagfishes have pinkish gray, wormlike bodies,
  secrete incredible amounts of slime, and tie
  themselves into knots.

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Sharks and Their Relatives

• Jaws make it possible to bite and chew plants and
  other animals
• Evolved paired pectoral (anterior) and pelvic
  (posterior) fins
• Paired fins offered more control of body movement
• Tail fins and powerful muscles gave greater
  thrust.

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Chondrichthyes

• Cartilaginous fishes
• Sharks, rays, and skates
• Paired fins and tail fins.

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Osteichthyes

• Bony Fishes
• Skeletons made of true bone
• Ray finned fishes
• Lobe finned fishes.

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Ray-Finned Fishes

• Aquatic vertebrates with skeletons of true bone
  most have paired fins, scales, and gills
• Most fishes you are familiar with
• Eels, catfish, walleye.

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Lobe-Finned Fishes

• Bony fishes that evolved fleshy fins supported by
  larger, more substantial bones
• Lungfishes and coelacanths
• Other ancient lobe-finned fishes evolved into the
  ancestors of tetrapods
• Four-limbed vertebrates.

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The Unique Fishapod

• Series of transitional fossils have been
  discovered that document the skeletal
  transformation from lobe-fins to limbs.

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Amphibians

• Vertebrates that, with some exceptions, require
  water for reproduction, breathe with lungs as
  adults, have moist skin with mucous glands, and
  lack scales and claws.

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Reptiles

• First vertebrates to evolve adaptations to drier
  conditions
• Vertebrate with dry, scaly skin, well-developed
  lungs, strong limbs, and shelled eggs that do not
  develop in water.

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• Current hypotheses about the relationships
  between living and extinct reptiles.

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Enter the Dinosaurs

• Triassic and Jurassic periods saw a great
  adaptive radiation of reptiles
• Lived all over the world, and they were diverse
  in appearance and in habit.

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Exit the Dinosaurs

• End of the Cretaceous Period
• Worldwide mass extinction cause by
• Series of natural disasters
• String of volcanic eruptions
• Fall in sea level
• Huge asteroid smashing into what is now the
  Yucatán Peninsula
• Many plant and animal groups went extinct.

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Bird Roots

• Support for hypothesis that birds evolved from a
  group of dinosaurs
• Archaeopteryx shows both bird characteristics
  (flight feathers) and dinosaur characteristics
  (teeth and bony tail).

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Birds

• Reptiles that regulate their internal body
  temperature (endothermy)
• Outer covering of feathers strong yet
  lightweight bones two legs covered with scales
  that are used for walking or perching and front
  limbs modified into wings.

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• Bird clade is part of the clade containing
  dinosaurs
• Clade containing dinosaurs is part of a larger
  clade of reptiles
• Modern birds are also reptiles.

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Mammals

• Mammary glands in females that produce milk to
  nourish young, and hair
• Breathe air, have four-chambered hearts, and
  regulate their internal body temperature.

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The First Mammals

• Very small and resembled modern tree shrews
• Modern mammalian groups evolved during Triassic
• Mammals diversified, increased in size, and
  occupied many niches after dinosaur extinction.

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Modern Mammals

• Monotremes
• Egg laying mammals- platypus
• Marsupials
• Bear live young that usually complete their
  development in an external pouch
• Kangaroos, koalas, and wombats
• Placental mammals
• Embryos develop further while still inside the
  mother
• Care and nurse for young.