Lancelet: characteristics, its importance in evolution

TOPIC: Lancelet: characteristics, its importance in evolution. Phylogenesis of the phylum chordata excretory system. Developmental disordes of the excretory system in human

LANCELET
Lancelets: Translucent, Fish-shaped animals, small elongated marine invertebrates that resemble a fish but, lack jaws and obvious sense organs.
Ranging from the very small to the very large, from animals with shells to animals with fur, from those that fly to those that swim in the sea

CHARACTERISTIC OF LANCELET
At some time of its lifee cycle, a chordata has a notochord, a dorsal hollow tubular nerve cord, pharyngeal slits, endostyle/thyroid gland, and a post-anal tail.
They do not have a true brain, but the notochord extends into the head. They lack paired fins, jaw, sense organs, a heart and well defined brain.

LANCELET IMPORTANCE IN EVOLUTION
VERTEBRATES: Mmebers of of subphylum vertebrata.
Cephalochordates, commonly called amphioxus or lancelets, are marine invertebrate chordates. Such comparisons are also providing important biological insights into the functional biology of cephalochordates and the evolutionary origin of developmental mechanisms that led to the emergence of the vertebrate body plan.
Another veterbrate characteristics is called cephalization
Evolution and development of the cartilaginous skull: from a lancelet towards a human face

What did Lancelets evolve?
The researchers are trying to reconstruct what happened at the end of the Cambrian period 550 million years ago, when a creature similar to the lancelet evolved and diverged into three types of chordates: cephalocordates like the lancelet; urochordates like the sea squirt; and vertebrates like us.

Phylogenesis of the phylum chordata excretory system
Metabolic waste are excreted by segmentally arranged, ciliated Protonephridia that open into the Right atrium.
For many chordates, the urinary system is a critical component of the excretory system. It is made up of organs such as the kidneys and bladder, structures such as a urethra or cloaca, and even arteries such as the aorta.

Developmental disordes of the excretory system in human
Major Disorders of Excretory SystemUremia. Under this condition, the urea accumulation is comparatively high. Renal Failure. Renal Calculi or Kidney Stones. Nephritis or Bright's Disease. Hypertension due to Renin Secretion. Renal Tabular Acidosis. Diabetes Insipidus. Oedema.