ChordataChordata

By

Nicko and Cecil

http://www.devonianlife.com/Pteraspis.jpg

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.

Sample Animals

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

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.http://jomacdoom.files.wordpress.com/2009/08/hagfish.jpg

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.

http://people.cornellcollege.edu/b-hess/geo105/images/lamprey.jpg

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.

http://templecuttingedge.files.wordpress.com/2009/06/great-white-shark-1.jpg

http://www.itsallaboutfish.co.uk/Pictures/Manta%20rays.jpg

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.

http://bss.sfsu.edu/holzman/courses/Fall01%20projects/rainbowtrout%20fig2.jpg

Actinistia (coelacanths)

• Lobe-finned fish.• Thought to be extinct until 1938 when

fisherman discovered in West Indian Ocean.

http://www.foxnews.com/images/302823/0_61_070731_coelacanth.jpg

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.

http://www.mongabay.com/images/calacademy/600/lungfish_going_left.jpg

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.

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

http://library.thinkquest.org/C0124402/data/images/2/2skeleton.gif

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.

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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

http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb7pg1_files/34-02-ChordateCharacters-L.gif

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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 1

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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 opening15

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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

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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

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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

http://www.earthlife.net/fish/skeleton.html

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Quiz

What is a feature that is not unique to chordates?

a) Notochord

b) A hollow nerve cord

c) Mineralized mouthpieces

d) Pharyngeal slits

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Quiz

True or False:

All fish have bones composed of calcium carbonate

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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

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Quiz

True or False:

Sharks bones and teeth are made primarily out of cartilage

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