BZ 110 Lecture Notes - Lecture 6: Dioecy, Plant Reproductive Morphology, External Fertilization
Document Summary
Unique combination of 5 characteristics notochord, pharyngeal slits or pouches, dorsal tubular nerve cord, post-anal tail, endostyle or thyroid gland. Slits openings between digestive tract and outside of body. In terrestrial vertebrates give rise the eustachian tube, middle ear cavity, tonsils and parathyroid glands. Located on pharyngeal flood of invertebrate chordates and larval lampreys. Most species are sessile as adults but some are planktonic. Tunic consists of proteins, salts and cellulose and is secreted by the epidermis. Trap phytoploankton and bacteria on a feeding filter inside their house. Nerve plexus in body wall with a single ganglion on pharynx. Numerous sensory receptors for mechanical and chemical stimuli distributed over body wall. Endostyle secretes mucus sheet which traps food particles. Ammonia diffuses into water that passes thru pharynx. Endostyle secretes mucus that wraps food on gill bars. Gametes shed into atrium and exit via atriopore. Free swimming larvae settle and metamorphose to adults.
