Characteristics of Invertebrate chordates 10/B (Notocord (The notochord is…
Characteristics of Invertebrate chordates 10/B
A structure used primarily for locomotion.
Located behind the digestive system and anus
In most chordates the post-anal tail extends beyond the anus.
With its muscle segments it can propel an animal with more powerful movement than chordates without post-anal tail.
Ancestral thyroid gland
A structure that regulates metabolism, growth, and development.
An early form of a thyroid gland had its origins in cells of early chordates that secreted mucus as an aid in filter feeding.
Invertebrate chordates have an endostyle-cells in the same area that secretes proteins similar to those secreted by thyroid gland.
All embryos have a pair of pharyngeal pouches that connect the mouth cavity to the esophagus.
Land (terrestrial) chordates
the pharyngeal pouches do not have slits and develop into other structures. These pouches are evidence of aquatic ancestry of all vertebrates
first used for filter feeding Later, they evolved into gills for gas exchange in water.
Dorsal tubular nerve cord (Modi):
chordates have dorsal tubular nerve cord which is tube shaped and located dorsal to (above) the digestive organs
During development, the anterior cord becomes the brain and the posterior cord becomes the spinal cord
the nerve cords in nonchordates are solid and located below the digestive system
The notochord is a flexible rod-like structure that extends the length of the body.
It is located just below the dorsal tubular nerve cord and is eventually replaced by bone or cartilage.
The flexibility of the notochord enables the body to bend rather than shorten during the contractions of the muscle segments.
In invertebrate chordates, the notochord remains.
An animal with a notochord can make side to side movements with their body and tail, making fishlike swimming possible for the first time in history.