Hemichordate or its functions

What is hemichordate?

Hemichordates exhibit a distinctive division of their body into three parts. The front section of their body features a preoral lobe, followed by a collar, and finally, a trunk. The name "hemichordate" means "half chordate," and hemichordates share some (but not all species) of the typical chordate characteristics.

It is a small phylum of marine invertebrates that comprises acorn worms.

The name is Hemichordate, meaning half chordate, and derives from their having only some characteristics of Chordates while lacking others. 

Hemichordate or its functions

General characteristics of hemichordates

1. Primarily dwelling in the marine environment, these organisms can be found either in solitude or in colonies, with a preference for constructing tubes as their abodes. 

2. The body is soft, delicate, worm-like, without segments, with bilateral symmetry, and composed of three germ layers.

3. The body is usually categorized into three distinct sections: the proboscis, collar, and trunk.

4. The body wall consists of a single-layered epidermis that is devoid of a dermis. Additionally, it contains mucous glands.

5. The coelom is an enterocoelous cavity, typically separated into three regions known as the protocoel, mesocoel, and metacoel.

6. Digestive tube complete, straight, or U-shaped. 

7. The foregut releases a hollow buccal diverticulum into the proboscis, which was previously referred to as the "notochord."

8. Dorso-lateral pharyngeal gill slits, if they exist, can be found in one to several pairs. These slits serve as passageways for filter-feeding organisms that use cilia to capture food particles from the surrounding water.

9. The circulatory system is uncomplicated and open, consisting of a dorsal heart and two elongated vessels—one positioned dorsally and the other ventrally.

10. Excretion through a Singular Proboscis Gland or Glomerulus Linked to Blood Vessels

11. Neural system primitive consisting mainly of a subepidermal 

Hemichordates

12. Reproduction is mainly sexual. Sexes are usually separate. Gonads/ nerve plexus. The dorsal collar nerve cord hollows in one to several pairs. 

13. Fertilization external, in seawater. Development direct or indirect development with a free-swimming tornaria larva.

14. They have soft, fragile, vermiform, unsegmented, bilaterally symmetrical, and triploblastic, their body is soft, fragile, vermiform, unsegmented, bilaterally symmetrical, and triploblastic.

15. Pharyngeal gill slits are located dorsally in non-vertebrates and hemichordates. These are sequential openings that are present along the pharynx, situated behind the mouth. Pharyngeal gill slits play a vital role in facilitating the flow of water into the mouth.

MCQs on Hemichordate

Here are 15 multiple-choice questions with answers about hemichordates:

Q. Hemichordates are distinguished by a tripartite division of the body consisting of:

   a) Head, thorax, and abdomen

   b) Proboscis, collar, and trunk

   c) Anterior, posterior, and dorsal regions

   d) Exoskeleton, endoskeleton, and exoskeleton

Answer: b) Proboscis, collar, and trunk

Q. The name "hemichordate" means:

   a) Half chordate

   b) Invertebrate marine organism

   c) Soft-bodied creature

   d) Chordate without a backbone

Answer: a) Half chordate

Q. Hemichordates primarily inhabit which environment?

   a) Terrestrial habitats

   b) Freshwater ecosystems

   c) Oceanic environments

   d) Forests and jungles

Answer: c) Oceanic environments

Q. Which phylum do hemichordates belong to?

   a) Arthropoda

   b) Mollusca

   c) Chordata

   d) Hemichordata

Answer: d) Hemichordata

Q. Hemichordates are commonly known as:

   a) Acorn worms

   b) Sea stars

   c) Jellyfish

   d) Coral reefs

Answer: a) Acorn worms

Q. The body of hemichordates is typically divided into how many distinct regions?

   a) 2

   b) 4

   c) 3

   d) 5

Answer: c) 3

Q. What type of body symmetry do hemichordates exhibit?

   a) Radial symmetry

   b) Asymmetry

   c) Bilateral symmetry

   d) Spherical symmetry

Answer: c) Bilateral symmetry

Q. Hemichordates possess a complete and straight or U-shaped:

   a) Respiratory system

   b) Digestive tube

   c) Circulatory system

   d) Nervous system

Answer: b) Digestive tube

Q. The circulatory system of hemichordates is:

   a) Complex and closed

   b) Simple and open

   c) Absent

   d) Divided into chambers

Answer: b) Simple and open

Q. Hemichordates primarily obtain nutrition through:

    a) Photosynthesis

    b) Predation on other organisms

    c) Filter feeding

    d) Absorption from the environment

Answer: c) Filter feeding

Q. Which system in hemichordates is considered primitive and consists mainly of a subepidermal structure?

    a) Digestive system

    b) Excretory system

    c) Respiratory system

    d) Nervous system

Answer: d) Nervous system

Q. Hemichordates reproduce mainly through:

    a) Asexual reproduction

    b) Internal fertilization

    c) Budding

    d) External fertilization

Answer: d) External fertilization

Q. The larval stage of hemichordates is called:

    a) Tornaria

    b) Plankton

    c) Metamorphosis

    d) Nematocyst

Answer: a) Tornaria

Q. Hemichordates possess which type of gill slits?

    a) Ventral

    b) Lateral

    c) Dorsal

    d) Bilateral

Answer: c) Dorsal

Q. Pharyngeal gill slits in hemichordates

 are used for:

    a) Reproduction

    b) Gas exchange

    c) Feeding and water movement

    d) Sensory perception

Answer: c) Feeding and water movement