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BIOL 108 Chp 11-pt 2: Animal Diversification
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BIOL 108 Chp 11-pt 2: Animal Diversification

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  • 1. Chapter 11 Animal Diversification Part 2 BIOL 108 Intro to Bio Sci Rob Swatski Assoc Prof Biology HACC-York
  • 2. 11.13–11.15 The phylum Chordata includes vertebrates, animals with a backbone.
  • 3. 11.13 All vertebrates are members of the phylum Chordata.
  • 4. Four distinct features of chordates
  • 5. The Notochord  A rod of tissue extending from the head to the tail  Stiffens the body when muscles contract during locomotion  In advanced chordates • Present only in early embryos • Replaced by the vertebral column (backbone)
  • 6. A Dorsal Hollow Nerve Cord  Extends from head to tail  In vertebrates, forms the central nervous system (spinal cord and brain)  In other animals, lies in lower portion of ventral part of body (and is solid instead of hollow)
  • 7. Pharyngeal Slits  Pharyngeal region • The area between the back of the mouth and the top of the throat  Pharyngeal slits are present in the embryos of all chordates.  Originally used for breathing and feeding
  • 8. A Post-Anal Tail  Extends back beyond the end of the trunk
  • 9. The phylum Chordata contains three sub-phyla:
  • 10. The Vertebrates: The Most Diverse Subphylum of Chordates
  • 11. Vertebrates differ from the other chordates in two important ways: 1. They have a backbone. 2. They have a head.
  • 12. Take-home message 11.13 All chordates have four characteristic structures: 1. A notochord 2. A dorsal hollow nerve cord 3. Pharyngeal gills slits 4. A post-anal tail
  • 13. Take-home message 11.13  The three subphyla of chordates are superficially very different, but are united by possessing these four structures at some stage of their life cycle.
  • 14. 11.14 The evolution of jaws and fins gave rise to the vast diversity of vertebrate species.
  • 15. The evolution of fins paralleled the evolution of jaws because the two structures work together.
  • 16. Fins get you to the organism you are going to eat. Jaws capture and kill it.
  • 17. Take-home message 11.14  The development of two structures—fins and jaws—set the stage for the enormous diversity of modern vertebrates.
  • 18. 11.15 The movement onto land required lungs, a rigid backbone, four legs, and eggs that resist drying.
  • 19. Take-home message 11.15  In the transition of vertebrates from life in water to life on land: • Fins were modified into limbs. • Vertebrae were modified to transmit the body weight through the limbs to the ground. • The site of gas exchange was transferred from gills and swim bladders to lungs.
  • 20. Take-home message 11.15  The only entirely new feature to appear in the early development of terrestrial vertebrates was an egg that resisted drying out.
  • 21. 11.16–11.20 All terrestrial vertebrates are tetrapods. Amniotes and non-amniotes
  • 22. 11.16 Amphibians live a double life.
  • 23. Take-home message 11.16  Amphibians are terrestrial vertebrates, but the adults of most species still lay eggs in water.  The eggs hatch into aquatic juveniles.
  • 24. 11.17 Birds are reptiles in which feathers evolved.
  • 25. Feathers
  • 26. Take-home message 11.17  Birds are a branch of the reptile lineage but, unlike other reptiles, possess feathers and can generate body heat.  The complex anatomical and physiological systems that we see in extant animals, such as feathers and endothermy in birds, are the products of hundreds of millions of years of stepby-step changes that began with simple structures.
  • 27. Take-home message 11.17  Feathers were originally colorful structures used for behavioral displays; additional functions such as insulation and flight evolved later.
  • 28. 11.18 Mammals are animals that have hair and produce milk.
  • 29. Are all mammals viviparous?  Viviparity—giving birth to babies rather than laying eggs  Monotremes lay eggs, but also produce milk.
  • 30. Take-home message 11.18  Hair and mammary glands are defining characteristics of mammals.  Monotremes are egg-laying  Marsupial mammals. mammals give birth after a short period of development in the uterus, and the newborn completes its development in the mother’s pouch.
  • 31. Take-home message 11.18  Placental mammals have a placenta that provides oxygen and nutrients to the fetus as it undergoes a longer development in the uterus.
  • 32. Take-home message 11.19  Humans’ forward-looking eyes, hands and feet with ten fingers and ten toes, and shoulder and elbow joints that allow the arms to rotate are characteristics we retain from our arboreal ancestors.
  • 33. Take-home message 11.19  The early ancestors of humans, however, left the trees and took up life on the ground where they walked on two legs.  Our success can be traced to an increase in brain size combined with a generalized body form and a diet that included both animals and plants.

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