Lancelet, characteristics, its importance in evolution

The lancelets (/ˈlænslɪts/ or /ˈlɑːnslɪts/), also known as amphioxi (singular: amphioxus /æmfiˈɒksəs/), consist of some 30–35 species of "fish-like" benthic filter feeding chordates [2] in the order Amphioxiformes. They are the modern representatives of the subphylum Cephalochordata. Lancelets closely resemble, and are believed to be related to, 530-million-year-old Pikaia, fossils of which are known from the Burgess Shale. Zoologists are interested in them because they provide evolutionary insight into the origins of vertebrates. Lancelets contain many organs and organ systems that are closely related to those of modern fish, but in more primitive form. Therefore, they provide a number of examples of possible evolution exaptation.
General introduction

The dorsal hollow nerve cord is part of the chordate central nervous system.In vertebrate fishes, the pharyngeal slits become the gills.Humans are not chordates because humans do not have a tail.Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column.The endostyle secretes steroid hormones
Features of lancelets

General characteristics and features of lancelets
The five characteristic features of chordates present during some time of their life cycles are a notochord, a dorsal hollow tubular nerve cord, pharyngeal slits, endostyle/thyroid gland, and a post-anal tail.

IMPORTANCE IN EVOLUTION
As the amphioxus lineage has likely been separated from other chordates for a very long time and displays a marked left-right asymmetry, its evolutionary history is potentially helpful in better understanding chordate and vertebrate origins. We studied the phylogenetic relationships within the extant amphioxus lineage based on mitochondrial genomes incorporating new Asymmetron and Epigonichthys populations, and based on previously reported nuclear transcriptomes. The resulting tree patterns are consistent, showing the Asymmetron clade diverging first, followed by the Epigonichthys and Branchiostoma clades splitting

EVOLUTIONARY CHANGES

Life cycle of lancelets

Phylogenesis of excretory system of phylum chordata
You have likely heard of the phylum Chordata because you yourself are part of this diverse group of animals. 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, Chordata incorporates a vast group of animals all over the planet.And while they may not all look the same, they are similar in that they produce wastes through metabolic processes and these wastes need to be removed from their bodies. This is accomplished in a number of different ways depending on the animal. These processes are performed by the excretory system, which quite literally serves to excrete wastes from the body.

Phylogenesis of excretory system of phylum chordata

Developmental disorders
Congenital anomalies of kidney and urinary tract (CAKUT) is a group of abnormalities affecting the kidneys or other structures of the urinary tract. The additional parts of the urinary tract that may be affected include the bladder, the tubes that carry urine from each kidney to the bladder (the ureters), and the tube that carries urine from the bladder out of the body (the urethra). CAKUT results from abnormal development of the urinary system and is present from birth (congenital), although the abnormality may not become apparent until later in life.

Classification of Development abnormalities
Many different developmental abnormalities are classified as CAKUT, including underdevelopment or absence of a kidney (renal hypodysplasia or agenesis), a kidney formed of fluid-filled sacs called cysts (multicystic dysplastic kidney), buildup of urine in the kidneys (hydronephrosis), an extra ureter leading to the kidney (duplex kidney or duplicated collecting system), a blockage in a ureter where it joins the kidney (ureteropelvic junction obstruction), an abnormally wide ureter (megaureter), backflow of urine from the bladder into the ureter (vesicoureteral reflux), and an abnormal membrane in the urethra that blocks the flow of urine out of the bladder (posterior urethral valve).

References
https://www.nature.com/articles/s41598-017-00786
-5https://study.com/academy/lesson/chordata-excretory-system.html
https://ghr.nlm.nih.gov/condition/congenital-anomalies-of-kidney-and-urinary-tract