Name the four 'hallmarks' of chordates and explain the principle function of each of them.
Answers
The functions of each of these are..
i. Notochord: It is the first part of the endoskeleton to appear in the embryo. The notochord is an axis for muscle attachment.
ii. Dorsal Tubular Nerve Cord: nerve cord found in all chordates that forms the spinal cord and brain.
iii. Pharyngeal Pouches and Slits openings that lead from the pharyngeal cavity to the outside. They are formed by inpocketing of the outside ectoderm and evagination, or outpocketing of the endodermal lining of the pharynx.
iv. Postanal Tail provides the motility that larval tunicates and amphioxus need for their free-swimming existance.
Answer:
hallmarks of chordates
Explanation:
1. Notochord-
*It is a flexible, rod-like structure located in the middorsal line between gut and nerve cord.
*derived from embryonic chordamesoderm.
*persists throughout life in lancelets and cyclostomes and in vertebrates is replaced by the vertebral column.
*It gives support to the body and provides space for attachement of bones.
2. Nerve cord-
*A single, hollow, tubular, non-ganglionated nerve cord situated above the notochord and the dorsal wall.
*derived from neural ectoderm in the embryonic stage.
*in higher chordates it is differentiated into the anterior brain and posterior spinal cord.
*function is the coordination of body activities.
3. Pharyngeal gill slits-
*These are a series of openings on the wall of the pharynx.
*ecto-endodermal in origin.
*In protochordates help in filter-feeding and in higher animals help in respiration.
4. Post anal tail-
*It is the posterior elongation of the body extending beyond the anus and cloaca.
*tail has no coelom and visceral organs but contains skeletal elements and muscles.
*It is useful in locomotion.