4 phylem of of protochordata
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Answer:
The organisms belonging to the Protochordata are generally known as the lower chordates. They don’t form a “proper” taxonomic group and are only classified as such for convenience purposes. However, they do form a major division of Chordata. They are also known as Acraniata because they lack a true skull. They are divided into three sub-phyla- Hemichordata, Urochordata, Cephalochordata.
Characteristics of Protochordata
They are generally found in marine water.
Their body is bilaterally symmetrical, triploblastic, and coelomated.
At a certain stage of their lives, their body develops a long, rod-like structure for support called notochord.
They exhibit organ system level of organization.
Eg., Herdmania, Amphioxus.
Classifications of Protochordata
Hemichordata
They are found in marine water.
Some live solitarily, and some stay in colonies.
The body is cylindrical, unsegmented, and stout.
The body is divided into proboscis, collar, and trunk.
The collar bears arms and tentacles.
They have a complete digestive system.
They respire through gills or general body surface.
The circulatory system comprises of a heart with two longitudinal vessels.
The blood has no colour and corpuscles.
The proboscis gland or glomerulus make up the excretory system.
Sexes may be separate or united and fertilization is either internal or external.
Eg., Cephalodiscus, Rhabdopeura
Urochordata or Tunicata