The Chordates

1. The Chordates

3. The Chordates CHARACTERISTICS: • Dorsal nerve (Spinal) cord • Notochord or backbone/vertebrae • Tail (at some stage of the life cycle) • Muscle Blocks • Gill Slits (at some stage of the life cycle

4. General Chordate Body Plan

5. The nerve or spinal cord connects the elongated body to the brain. • Nerve signals are sent quickly • Organisms can grow larger, able to survive and respond to environment

6. The notochord/backbone/vertebrae adds strength and protection for the spinal cord • Organism can grow larger • Provides attachment for muscles (stronger)

7. Tail is an adaptation for locomotion, balance, & propulsion.

8. Gill slits evolved as an adaptation for exchange of respiratory gases = larger and/or faster animals. • From gills jaws evolved for more advanced vertebrates.

9. Compared to the Invertebrates, the Chordates are: • Smarter • Larger • More coordinated • Faster

10. Three Divisions of Chordates: • Urochordates • Cephalochordates • Vertebrates

11. Urochordata • also known as Tunicates • or Sea Squirts. • live in salt water (marine) • - are free-floating or sessile. • chordate features are most evident in the larvae (Illustration from Linzey, 2001)

12. Cephalochordata • - aka “lancelets” ex. Amphioxus • - are marine - live in sand or shallow water. • - adults possess all chordate features

13. Vertebrata • Some of the 5 chordate features are evident only during development • - Embryonic vertebrates have: • - a notochord • - dorsal nerve chord • - gill slits/pouches • (pharyngeal clefts)

14. Vertebrate Origins • What is the ancestral origin of the Vertebrates/Chordates? • no fossil record, therefore only based on speculation • one popular hypothesis puts the chordates as possibly descendant from the same common ancestor of echinoderms??

15. FromRomer

16. Vertebrata 5 classes: • fish • amphibians • reptiles • birds • mammals

17. Fish • First appear in the Paleozoic Era • Devonian Period is “The Age of Fishes”

18. Fish are more advanced over their invertebrate ancestors, in that they (the advanced fish) possess: • Skull • Bones (either cartilaginous or calcified) • Jaws (which evolved from gill slits) • Fins (paired appendages, different from the appendages of the invertebrates)

19. Fish Subdivisions • Agnathans • Placoderms • Chondrichthyes • Osteichthyes

20. Agnathans • No jaws – jawless • Cartilage skeletons • Lampreys and hagfish

21. Placoderms • First fish to have jaws, vertebrae and paired fins • They are now extinct – below are pictures reconstructed from fossils:

22. Jaws evolved when gill openings became enlarged and fitted with teeth – allowing consumption of more food = greater size.

23. Placoderms

24. Vertebrae evolved to enclose the spinal cord – adding protection and attachment for muscles = more powerful movements.

25. Paired fins improved swimming = faster and more manoeuvrability.

26. Other Interesting Facts about Fish: • Have a 2 chambered heart & a closed circulatory system • Are cold blooded (ectotherms) • Sexually reproduce, but use external fertilization (males don’t have a penis!) • Produce jelly-like eggs that must be laid in water

27. Chondrichthyes • Skulls smaller – lighter weight • Skeletons of cartilage – very flexible and light weight – for greater agility and speed Sharks and Rays

28. Osteichthyes • The Bony Fishes • Two types: 1) Lobe Finned Fish 2)Teleosts

29. Lobe Finned Fish • Lobes fins allow them to walk on the bottom or even on land • Had primitive lungs for breathing –, could be out of water for short periods of time • Modern day lung fish, coelocanthes, and amphibians evolved from these • http://www.youtube.com/watch?v=D1UKHimLZao • http://www.youtube.com/watch?v=NTtwQmbCk_4

30. Teleosts – Spiny Finned Fish • Modern fish • Fins have spines for support • Have a swim bladder to help them be buoyant at any depth

31. Amphibians Frogs, toads, newts and salamanders In addition to the innovations accomplished by fish, amphibians have: • Legs that extend sideways – awkward for both swimming and walking – but better than lobes • Lungs – (though the lobe finned lung fish also had lungs) • 3 chambered heart

32. Crocodiles & Snakes Reptiles Turtles & Lizards

33. And Don’t Forget… Dinosaurs were reptiles too!!

34. In addition to the amphibian characteristics, reptiles have characteristics that allow them to be away from water for longer, move better and grow larger: • Dry scaly skin (prevented drying out of skin, but also prevented breathing thru skin) • Expandable rib cage (allowed them to inflate their lungs to a large volume)

35. Leather shelled amniote eggs (allowed them to lay their eggs away from water) • Copulatory organs (i.e. a penis - for internal fertilization – the only way for sperms to get to eggs when animals are living on land !!) • Legs extending beneath the body (for better locomotion & supporting more weight) • 3 and 1/2 chamber heart (for better separation of oxygenated and deoxygenated blood – richer blood – more energy)

36. Birds Improvements over reptiles include: • Feathers (for insulation and flight) • Hollow bones (lighter weight for flight)

37. Warm blooded (allowing for greater energy production) • Air sacs (for greater surface area and gas exchange) • 4 chamber heart (for complete separation of oxygenated and deoxyg. blood = richer blood = more energy) • Hard shelled amniote egg (more protection from drying out and from predators)

38. Mammals • The Cenozoic Era is known as the “Age of Mammals” • In addition to warm blood and a 4 chambered heart, mammals also possess: • Milk and Mammary glands (to nourish young) • Body hair (for insulation) • 3 groups: placentals, monotremes, and marsupials

39. Placentals • Possess a placenta which supports growth of the embryo until birth – better chance of survival

40. Monotremes • Lay leathery eggs (like reptiles) Echidna (spiny ant-eater) platypus

41. Marsupials • Give birth to an immature live young - no larger than a kidney bean • Wombats, opossums, kangaroos, koalas