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Chordata By Nicko and Cecil

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1 Chordata By Nicko and Cecil

2 Phylum: Chordates - Bilaterian (bilaterally symmetrical) animals. All chordates share a notocord, a dorsel, hollow nerve cord, pharyngeal slits of clefts and a muscular post-anal tail at one point in their lifetime (may only be in embyronic development). There are eleven major groups of chordates but six groups of fish.

3 Sample Animals Six major groups of fish. –Myxini (hagfish) –Cephalaspidomorphi (lampreys) –Chondrichthyes (sharks and rays) –Actinopterygii (ray-finned fishes) –Actinistia (coelacanths) –Dipnoi (lungfishes)

4 Myxini (hagfish): The only fish that still survives from this group are hagfishes. Skulls made of cartilage and lack jaws and vertebrae. Small brain, eyes, ears and nasal openings that connects with the pharynx, and slime glands. Bottom dwelling scavengers.

5 Cephalaspidomorphi (lampreys) Oldest living lineage of vertebraes. The skeleton is made of cartilage that contains no collagen and they lack jaws. Most are parasitic feeders.

6 Chondrichthyes (sharks and rays) Most successful vertebrae predators in the ocean. Have a skeleton composed predominantly of cartilage often impregnated with calcium. Lay eggs that hatch outside the mothers body. Larger sharks and rays are suspension feeders. Most sharks are carnivores.

7 Actinopterygii (ray-finned fishes) Most fish familiar to us belong to this phylum. The fins are modified for maneuvering, defense and other functions. Some species include bass, trout, herring, etc.

8 Actinistia (coelacanths) Lobe-finned fish. Thought to be extinct until 1938 when fisherman discovered in West Indian Ocean.

9 Dipnoi (lungfishes) The second lineage of living lobe-fins. All are found in the Southern Hemisphere. Only found in fresh water, generally in stagnant ponds and swamps. Can gather oxygen from both the air through their pharynx and the water through their gills.

10 Body Cavity/Symmetry Three distinctive characteristics that make chordata unique: –Notochord. –Hollow nerve cord that lies dorsal to the notochord. –Pharyngeal pouches. All chordates have a coelom. Most chordates have bilateral symmetry.

11 Nervous System Has a brain and a central nervous system. Have a lateral line system that helps them detect prey. The hollow nerve cord is what develops into the spine

12 Other Body Systems Circulatory System –Cold blooded. –Contains a heart, blood and blood vessels. Digestive System –Eats algae and plants/animals. –Those that eat animals have teeth. Excretory System –A fish gets rid of waste through the anus.

13 13 Locomotion/Musculature The notochord not only provides support, but is also a key element muscles use during swimming All chordates have post-anal tails, however some are lost during embryonic development Many fish use these tails, which move in a vacillating motion, as the main force that propels them through the water

14 14 Skeletal Type The notochord is a long flexible composed of fluid filled cells encased by fibrous tissue is located between the digestive tube and the nerve cord However, many species can also lose the notochord in embryonic development As a result, a much more complex joint skeleton forms Only ray-finned and lobe-finned skeletons are not composed primarily of cartilage Ray-finned and lobe-finned fish contain bones made of calcium phosphate 14

15 15 Sensory structures/features Have eyes, but no eyelids Retinas contain both and cones and pupils let in a great deal of light Have nasal passages that connect with the pharynx Some fish have a nasal sac that also connects to the nasal passage that improves their sense of smell Have inner ears, but no outer ear opening 15

16 16 Reproduction Methods Reproduce sexually Female lays her eggs Male comes and fertilizes the eggs (sprays a substance called milt, which contains sperm) However, some females carry their eggs until birth Egg contains a yolk that nourishes the fish 16

17 17 Gas Exchange Acquire oxygen and release acrbon dioxide through pharyngeal slits (gills) Pharyngeal slits are composed of threadlike filaments When water passes through the pharyngeal slits, the blood vessels within the filaments absorb oxygen and release carbon dioxide 17

18 18 Other Unique features Chordates are the only animals with hollow nerve cords All other animals have solid nerve cords Ray-finned fish were the first animals to have bones composed of calcium carbonate Conodonts were the first animals to have mineralized mouth parts

19 19 Quiz What is a feature that is not unique to chordates? a) Notochord b) A hollow nerve cord c) Mineralized mouthpieces d) Pharyngeal slits 19

20 20 Quiz True or False: All fish have bones composed of calcium carbonate 20

21 21 Quiz Which part of the circulatory system do fish not have? a) Blood b) Blood vessels c) Heart d) They have all of the above 21

22 22 Quiz True or False: Sharks bones and teeth are made primarily out of cartilage 22

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