Chordates Chap 27

1
Chordates (Chap 27)
2
Kingdom AnimaliaPhylum Chordata (evolved 535
mya)

• All chordates have the following features at
  some point in their life (may only be present in
  the embryo)
• pharyngeal slits - a series of openings that
  connect the inside of the throat to the outside
  of the "neck". These are often, but not always,
  used as gills.
• dorsal nerve cord - a bundle of nerve fibers
  which runs down the "back". It connects the brain
  with the lateral muscles and other organs.

3

• notochord - cartilaginous rod running underneath,
  and supporting, the nerve cord.
• post-anal tail - an extension of the body past
  the anal opening.

4
Subphylum Vertebrata (evolved 500mya)

• Characteristics
• have vertebral columns (backbones)
• brain enclosed in a cranium
• ventral heart
• gills or lungs
• two-- pairs of limbs, eyes, kidneys, sexes

5
7 Living Classes of Vertebrates

• 1. Agnatha
• marine animals
• lack jaws and paired fins
• skeletons of cartilage
• 75 sp. -- hagfish and lampreys

6
2. Chondrichthyes

• fishes with skeletons of cartilage
• skin is placoid scales miniature teeth embedded
  in the skin
• 700 sp. -- sharks, skates and rays

7
3. Osteichthyes

• bony fishes
• have a swim bladder
• have an operculum, a flap on each side of the
  fish that covers the gills
• over 29,000 species

8
4. Amphibia

• most develop and reproduce in water
• have primitive lungs
• moist skin for gas exchange
• 5700 sp. -- frogs, salamanders

9
5. Reptilia

• scales
• well-developed lungs
• most are terrestrial
• internal fertilization
• a leathery amniotic egg- embryo surrounded by a
  fluid-filled sac and membranes
• 6500 sp. -- turtles, snakes, lizards

10
6. Aves

• light and strong skeleton
• beak, no teeth
• feathers
• large yolked, hard-shelled eggs
• enlarged sternum where flight muscles can attach
• 9000 sp.

11
7. Mammals