Download Chordates

Chordates
Ch. 30.1
• From the Phylum CHORDATA (kingdom ANIMALIA)
• Must have 4 characteristics at some point during their life
cycle
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Dorsal, hollow nerve cord
Notochord
Pharyngeal pouch
Tail that extends past the anus
What is a chordate
• Dorsal nerve cord is on the BACK of the body.
• Nerves BRANCH off the cord
• Helps connect internal organs, muscles, and sensory organs
• Notochord is a long supporting rod just below the nerve
cord.
• Typically only around when the organism is still an embryo
• Pharyngeal pouches are paired structures in the pharynx
(throat) region
• In fish and amphibians these pouches connect to form slits
outside the body (used as gills for breathing/gas exchange)
• All chordates have a tail that extends beyond their anus.
• Contains bone and muscle
• Used for swimming in aquatic species
• 99% of chordates are in the subphylum VERTEBRATA
• Vertebrates are chordates with a vertebral column/backbone
• The dorsal nerve cord is then called the SPINAL CORD
• Front end of spinal cord forms a brain
• Backbone is made of individual segments called
vertebrate (protect the spinal cord)
Most Chordates are
Vertebrates
• Backbone is part of the ENDOSKELETON (internal
skeleton)
• Offers support and protection
• Muscle attachment
• Skeleton continues to grow as the animal grows.
• These chordates do NOT have backbones
• Nonvertebrate chordates and tunicates and lancelets
• Soft bodies marine organisms
• Still have the 4 requirements to be a chordate
• Embryology and structure has shown that nonvertebrate
chordates and chordates evolved from the same ancestor
Nonvertebrate Chordates
• Tunicates are filter feeders
• Larval form have the characteristics of chordates; adults
do not (no notochord or tail)
• Lancelets live on the sandy ocean bottoms
• Use pharynx for eating, not gas exchange
• Closed circulatory system
Tunicates and Lancelets