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Why is it called Hemichordata?

The name Hemichordate, meaning half chordate, derives from their having only some characteristics of Chordates, while lacking others. They are deuterostomes characterized by embryonic development where the first opening (the blastopore) becomes the anus, in contrast to protostomes where it becomes the mouth.

What are the different body parts of Hemichordates?

The hemichordate body is divided into three parts: proboscis (protostome), collar (mesosome) and trunk (metasome) – reflecting an underlying tricoelomate organization (see below).

What are the examples of Hemichordata?


What are the five identifying characteristics of the phylum Hemichordata?

They are exclusively marine, solitary or colonial, mostly tubicolous. Their body is soft, fragile, vermiform, unsegmented, bilaterally symmetrical, and triploblastic. The body is divisible into proboscis, collar, and trunk.

What is the difference between Hemichordata and Chordata?

Hemichordates are worm-like, marine animals while chordates live in water, land, and air. The main difference between Hemichordata and Chordata is that Hemichordata contains an epidermal nervous system whereas Chordata contains a central nervous system. Both Hemichordata and Chordata contain pharyngeal gill slits.

Do Hemichordates have a brain?

Rather it is only recently that the hemichordates were revealed to possess a centralized nervous system14. The presence of a central nervous system in protostomes and hemichordates indicates that the centralization of the nervous system occurred before the divergence of protostomes and deuterostomes14.

Is nerve cord present in Hemichordata?

In hemichordates, the dorsal nerve cord is present and it is restricted to the collar region of the body. It is not present throughout the body.

Which organ is present in Hemichordata instead of notochord?

Notochord in hemichordata is present in proboscis.

Do Hemichordates have heart?

It is present in earthworms. Hence the correct answer is B. The heart of Hemichordate is dorsal. Note: Open circulatory system is mainly found in in-vertebrates.

What is Stomochord in Balanoglossus?

The stomochord is a flexible, hollow tube found in hemichordates. Stomochords arise in embryonic development as an outpocketing from the roof of the embryonic gut anterior to the pharynx. In adults, they extend dorsally from the pharynx into the proboscis, and it communicates with the oral cavity.

Does all Hemichordates have Stomochord?

Notochord is found in all chordates. Stomochord is found in the hemichordates only. This structure provides support to the body. Chordates don’t have stomochords.

What is the difference between notochord and Stomochord?

The stomochord arises as an outgrowth from the outer cells of the embryonic gut whereas notochord is developed from cells from the mesoderm, which is a middle layer of the embryo. Stomocord helps in locomotion while notochord is supportive in function.

What is Pygochord?

Pygochord is longitudinal rod like structure extending from the ventral side of the intestine to the body wall, in the post hepatic region of the trunk. Its cells are vacuolated It supports the post hepatic region of the body but probably also performs some other functions not yet understood.

Does Balanoglossus have notochord?

Balanoglossus is a deuterostome, and resembles the Ascidians or sea squirts, in that it possesses branchial openings, or “gill slits”. It has notochord in the upper part of the body and has no nerve chord….

Genus: Balanoglossus Delle Chiaje, 1829
See text.

What is buccal diverticulum?

– So, buccal diverticulum is a thick walled projection that is extended towards the proboscis stalk inside the proboscis coelom. In short it is a tube like projection. It is tubular outgrowth from the cavity of mouth to the proboscis. The wall is made of a single layer of vacuolated and tall endodermal cells.

What is the function of buccal diverticulum?

(i) Buccal Diverticulum: Buccal diverticulum is a hollow preoral outgrowth, extending from the roof of the buccal cavity into the proboscis. It was for a long time also called a notochord or a stomochord on the assumption that it represents the anterior portion of the notochord of chordates.

Why Balanoglossus is called tongue worm?

Balanoglossus secretes iodoform like foul smelling compound as a defense mechanism Balanoglossus is used as fish-bait by local fishermen. It is also called Tongue worm due to the resemblance of the proboscis & genital wings to Ox tongue. Coelomic sacs are present in the body of Balanoglossus.

What kingdom does Tiger belong to?