Phylum - Hemichordata Questions in English

(A) $Balanoglossus$ is a representative organism of the phylum $Hemichordata$.
In animals of $Hemichordata$,the notochord is a rudimentary,short structure confined to the proboscis region,often referred to as the stomochord,and it is non-homologous to the true notochord found in chordates.

(B) The members of the phylum $Hemichordata$ are exclusively marine animals.
They are generally solitary or colonial and mostly live in tubes (tubicolous).

(A) The phylum $Hemichordata$ was previously considered a subphylum under $Chordata$.
However,it is now placed as a separate phylum.
The animals in this group possess a rudimentary structure in the collar region called the $stomochord$,which is often compared to the notochord.
In $Hemichordates$,this structure is restricted to the anterior part of the body,specifically the proboscis region.
Therefore,the correct group is $Hemichordata$.

(A) $Balanoglossus$ (a hemichordate) is considered a connecting link between echinoderms and chordates.
It possesses characteristics of both groups,such as a larval stage ($Tornaria$ larva) that resembles the bipinnaria larva of echinoderms,and chordate-like features such as pharyngeal gill slits and a dorsal nerve cord.

(A) $Balanoglossus$ belongs to the phylum Hemichordata. The characteristic larval stage of $Balanoglossus$ is called the $Tornaria$ larva. This larva is free-swimming and ciliated,showing significant similarities to the bipinnaria larva of echinoderms,which suggests an evolutionary link between the two groups.

(D) $Balanoglossus$ belongs to the phylum Hemichordata.
Within the phylum Hemichordata,it is classified under the class Enteropneusta,which are commonly known as acorn worms.
Therefore,the correct classification sequence is Chordata $\rightarrow$ Hemichordata $\rightarrow$ Enteropneusta.

(B) The phylum $Hemichordata$ was earlier considered as a sub-phylum under phylum $Chordata$.
However,it is now placed as a separate phylum under the non-chordates.
$Balanoglossus$ is a well-known example of the phylum $Hemichordata$.
$Herdmania$,$Branchiostoma$,and $Botryllus$ are members of the sub-phylum $Urochordata$ or $Cephalochordata$,which are true protochordates.

(D) . $Protochordates$ are primitive chordates. All $Protochordates$ are exclusively marine.

(B) The larval form of $Hemichordata$ (specifically in the class $Enteropneusta$,such as $Balanoglossus$) is known as the $Tornaria$ larva.
This larva is planktonic and bears a striking resemblance to the $Bipinnaria$ larva of $Echinodermata$,which suggests an evolutionary link between the two phyla.

(D) Earlier,$Balanoglossus$ was considered a part of the phylum $Chordata$ due to the presence of a structure thought to be a notochord. However,later studies revealed that this structure is actually a $stomachochord$ (a rudimentary structure in the proboscis). Consequently,it is now classified under the separate phylum $Hemichordata$.

(A) The body of $Balanoglossus$ (a member of Phylum Hemichordata) is divided into three distinct parts: a proboscis, a collar, and a trunk. $Amphioxus$ belongs to Cephalochordata, $Herdmania$ belongs to Urochordata, and $Petromyzon$ belongs to Cyclostomata. Therefore, the correct answer is $Balanoglossus$.

(D) Hemichordates were previously considered a sub-phylum under Phylum Chordata because they possess a structure called the stomochord in the collar region,which was earlier mistaken for a notochord.
However,the stomochord is not a true notochord as it is not mesodermal in origin and does not extend throughout the body length.
Furthermore,true chordates are characterized by the presence of a dorsal hollow nerve cord,which is absent in hemichordates (they possess a dorsal and ventral nerve cord).
Therefore,hemichordates are now placed in a separate phylum,and both statements $(B)$ and $(C)$ are valid reasons for their exclusion from Phylum Chordata.

(C) The size of sperm varies significantly across different species. Among the given options,$Balanoglossus$ (a hemichordate) is known to possess the smallest sperm cells. Sperm size is generally related to the reproductive strategy and the environment in which fertilization occurs.

(B) The phylum $Hemichordata$ consists of marine animals with an organ-system level of organization. Their body is cylindrical and is composed of an anterior proboscis,a collar,and a long trunk. $A$ characteristic feature of hemichordates is the presence of a $U$-shaped digestive tract,which is adapted for their filter-feeding lifestyle. Therefore,the correct option is $B$.

(D) The phylum $Hemichordata$ consists of a small group of worm-like marine animals.
These organisms are characterized by an organ-system level of body organization.
They are bilaterally symmetrical,triploblastic,and coelomate animals.
The body is cylindrical and is composed of an anterior $proboscis$,a $collar$,and a long $trunk$.
They are exclusively marine and can be found living either as solitary individuals or in colonies.

(D) The phylum $Hemichordata$ consists of worm-like marine animals.
These organisms are exclusively marine and are often found living in burrows or tubes in the sea floor.
They exhibit organ-system level of organization and are bilaterally symmetrical,triploblastic,and coelomate animals.
Therefore,the correct option is $D$.

(B) The phylum $Hemichordata$ consists of worm-like marine animals with an organ-system level of organization. Their body is cylindrical and is distinctively divided into three parts: a $proboscis$,a $collar$,and a $trunk$.

(C) The phylum $Hemichordata$ consists of a small group of worm-like marine animals with an organ-system level of organization.
In $Hemichordata$ (e.g.,$Balanoglossus$),excretion occurs through the $Proboscis$ $gland$ (also known as the $glomerulus$).
Flame cells are excretory structures in $Platyhelminthes$.
Green glands (antennary glands) are excretory organs in $Crustaceans$ (Arthropoda).
Malpighian tubules are the excretory organs in most $Insects$ (Arthropoda).

(A) The phylum $Hemichordata$ includes organisms like $Balanoglossus$ (acorn worms).
In their life cycle,they undergo indirect development,which involves a free-swimming larval stage known as the $Tornaria$ larva.
This larva shares structural similarities with the bipinnaria larva of echinoderms,suggesting an evolutionary link between the two groups.
Therefore,the correct option is $A$.

(C) $Balanoglossus$ is a classic example of the phylum $Hemichordata$.
It was previously considered a sub-phylum under $Chordata$ but is now placed as a separate phylum due to the presence of a rudimentary structure in the collar region called the $stomochord$,which is not a true $notochord$.

(C) Balanoglossus belongs to the phylum Hemichordata.
In Hemichordates,the excretory organ is the proboscis gland,also known as the glomerulus.
Flame cells are found in Platyhelminthes.
Nephridia are the excretory structures in Annelids.
Malpighian tubules are the excretory organs in insects and many other arthropods.

(B) The $U$-shaped digestive tract is a characteristic feature of the phylum $Hemichordata$. In these organisms,the mouth and anus are located close to each other,resulting in a $U$-shaped gut. For example,in $Balanoglossus$,the alimentary canal is $U$-shaped.

(C) The proboscis gland,also known as the glomerulus,is an excretory organ found in Hemichordates (e.g.,Balanoglossus).
It is located in the proboscis region and is associated with the blood vessels (or blood sinus) to filter metabolic wastes from the blood.
Therefore,it is primarily associated with the blood vessel/circulatory system for the purpose of excretion.

(A) In Hemichordata (e.g.,Balanoglossus),the alimentary canal is $U$-shaped. The mouth is located ventrally,and the anus is located at the posterior end of the body. The digestive tract is complete,consisting of a mouth,pharynx,esophagus,intestine,and anus.

(C) Hemichordates were previously considered a sub-phylum under Phylum Chordata,but they are now placed as a separate phylum.
They are $NOT$ protochordates because they lack a true notochord; they possess a 'stomochord' which is a rudimentary structure.
The digestive tract is complete and straight.
The circulatory system is of the open type,not closed.
Excretion occurs through the proboscis gland.
Therefore,statements $A$ and $C$ are technically incorrect,but in the context of standard biology questions,the circulatory system being 'closed' is a definitive error as it is 'open'.

(B) Hemichordates are a small group of worm-like marine animals. They exhibit organ-system level of organization. They are bilaterally symmetrical,triploblastic,and coelomate animals. $A$ key characteristic of many hemichordates (like Balanoglossus) is that they are tube-dwelling,meaning they live in burrows or tubes in the marine sediment. Therefore,they are described as worm-like,exclusively marine,and tube-dwelling organisms.

(A) The phylum $Hemichordata$ is characterized by the presence of a specific larval stage known as the $Tornaria$ larva. This larva is free-swimming and ciliated,showing significant similarities to the bipinnaria larva of echinoderms,which suggests an evolutionary link between the two groups. Other options like $Parenchymula$ and $Amphiblastula$ are associated with Porifera,while $Planula$ is characteristic of Cnidaria.

(A) The phylum $Hemichordata$ was earlier considered as a sub-phylum under the phylum $Chordata$. However,it is now placed as a separate phylum under the non-chordates. It exhibits characteristics of both $Echinodermata$ (e.g.,larval forms) and $Chordata$ (e.g.,stomochord). Therefore,it is phylogenetically placed between the phylum $Echinodermata$ and the phylum $Chordata$.

(B) In the phylum $Hemichordata$, the body is divided into three parts: proboscis, collar, and trunk.
Excretion in these animals occurs through the $Proboscis$ gland (also known as the glomerulus), which is located in the proboscis region.
$Nephridia$ are found in Annelids, $Kidneys$ are found in Chordates, and $Green$ glands are found in Crustaceans (Arthropods).

(C) Bilateral symmetry is a characteristic feature where the body can be divided into identical left and right halves in only one plane.
$1$. Sea cucumber (Echinodermata) exhibits radial symmetry in adults.
$2$. Hyalonema (Porifera) is asymmetrical.
$3$. Balanoglossus (Hemichordata) exhibits bilateral symmetry.
$4$. Spongilla (Porifera) is asymmetrical.
Therefore,the correct option is $C$.

(D) The proboscis gland (also known as the glomerulus) is the excretory organ found in Hemichordates. $Balanoglossus$ is a well-known member of the phylum Hemichordata. Therefore,it uses the proboscis gland for the process of excretion.

(A) The proboscis gland (also known as the glomerulus) is the excretory organ found in Hemichordates,such as Balanoglossus.
Balanoglossus belongs to the phylum Hemichordata.
The characteristic larva of Hemichordates is the Tornaria larva.
Therefore,the correct option is $A$.

(B) The phylum $Hemichordata$ consists of a small group of worm-like marine animals. Their body is cylindrical and is distinctively divided into three parts: an anterior $proboscis$,a collar,and a long trunk. Examples include $Balanoglossus$ and $Saccoglossus$.

(B) $Balanoglossus$ belongs to the phylum $Hemichordata$.
$1$. $Balanoglossus$ is dioecious,meaning the sexes are separate.
$2$. Fertilization is external,occurring in the surrounding water.
$3$. The development is indirect,involving a characteristic larval stage known as the $Tornaria$ larva.

(B) The correct answer is $B$.
An important characteristic that hemichordates and chordates share is the presence of pharyngeal gill slits.
In hemichordates,these gill slits are dorsal in position,whereas in chordates,they are lateral.
$A$ true notochord is absent in hemichordates; instead,they possess a structure called the stomochord.
The nervous system in hemichordates is intraepidermal,and they possess a ventral nerve cord,which differs from the dorsal hollow nerve cord found in chordates.

(C) $1$. Annelids (except leeches) typically have a closed circulatory system.
$2$. Protists are unicellular organisms and do not possess a circulatory system.
$3$. Hemichordates possess an open circulatory system.
$4$. Arthropods possess an open circulatory system.
Therefore,the correct pair is Open circulatory system - Hemichordata.

(C) Hemichordates were previously considered a sub-phylum of Chordata because they possess pharyngeal gill slits,which is a characteristic feature of chordates.
However,they lack a true notochord (they have a stomochord) and their nerve cord is not dorsal and hollow like in chordates.
Therefore,the presence of pharyngeal gill slits is the common feature shared between Hemichordata and Chordata.

(N/A) $\rightarrow$ Hemichordata was earlier considered as a sub-phylum under phylum Chordata.
$\rightarrow$ But now it is placed as a separate phylum under non-chordates.
$\rightarrow$ This phylum consists of a small group of worm-like marine animals with an organ-system level of organization.
$\rightarrow$ They are bilaterally symmetrical, triploblastic, and coelomate animals.
$\rightarrow$ The body is cylindrical and is composed of an anterior proboscis, a collar, and a long trunk.
$\rightarrow$ The circulatory system is of the open type.
$\rightarrow$ Respiration takes place through gills.
$\rightarrow$ The excretory organ is the proboscis gland.
$\rightarrow$ Sexes are separate.
$\rightarrow$ Fertilization is external.
$\rightarrow$ Development is indirect.
$\rightarrow$ Examples: Balanoglossus and Saccoglossus.

(D) Hemichordates are characterized by a soft,fragile,and worm-like appearance.
Their body is cylindrical in shape and is divided into three distinct parts:
$1$. Proboscis
$2$. Collar
$3$. Trunk

(C) The body of hemichordates is cylindrical and is divisible into three distinct regions: an anterior proboscis,a collar,and a long trunk.

(B) The name $Hemichordata$ literally means 'half chordates' and they act as a link between chordates and non-chordates.
$Hemichordata$ was earlier considered as a sub-phylum under the phylum $Chordata$,but now it is placed as a separate phylum under non-chordates.

(B) Excretion of nitrogenous waste in hemichordates takes place through the proboscis gland.
The gland collects waste from the blood and passes it into the coelom of the proboscis.
From there,it is excreted through the proboscis pore,located at the anterior region of the proboscis.

(A) Phylum Hemichordata consists of small group of worm-like marine animals with organ-system level of organization.
Balanoglossus and Saccoglossus are the classic examples of this phylum.
Salpa and Doliolum belong to Urochordata.
Petromyzon and Myxine belong to Cyclostomata (subphylum Vertebrata).
Dentalium and Chaetopleura belong to Mollusca.

(A) The $stomochord$ in $Hemichordata$ is not mesodermal in origin; it is an ectodermal structure.
Because it is not a true notochord (which is mesodermal),these organisms are classified as non-chordates.
The $stomochord$ is a blind projection arising from the roof of the buccal cavity,also known as the buccal diverticulum.
Therefore,the statement claiming it is mesodermal in origin is incorrect.

(A) Assertion is true: In $Balanoglossus$,the proboscis is involved in excretion.
$Balanoglossus$ belongs to the phylum $Hemichordata$,where the proboscis gland performs the excretory function.
Reason is also true: $A$ glomerulus is present in the proboscis,which is responsible for or mediates the excretory function of the proboscis gland.
Therefore,both Assertion and Reason are correct,and the Reason is the correct explanation for the Assertion.

(B) The phylum $Hemichordata$ consists of a small group of worm-like marine animals with an organ-system level of organization. Their body is cylindrical and is composed of an anterior $proboscis$,a $collar$,and a long $trunk$.

(A) The animal shown in the image is a Hemichordate,specifically a Balanoglossus (acorn worm).
In the phylum Hemichordata,fertilization is external,meaning it occurs outside the body in the surrounding water.
Development is indirect,which means it involves a larval stage (e.g.,the Tornaria larva) before reaching the adult form.
Therefore,the correct combination is external fertilization and indirect development.

(C) The correct answer is $C$ (Hemichordata).
$1$. $Hemichordata$ are bilaterally symmetrical animals.
$2$. $Echinodermata$ adults exhibit radial symmetry (specifically pentamerous radial symmetry),although their larvae are bilaterally symmetrical.
$3$. $Ctenophora$ exhibit radial symmetry.
$4$. $Coelenterata$ (Cnidaria) exhibit radial symmetry.
Therefore,radial symmetry is not found in the adults of $Hemichordata$.

(D) Hemichordates,such as $Balanoglossus$,possess a specialized structure for excretion known as the $Proboscis$ $gland$ or $Glomerulus$.
This organ is located in the proboscis region and is responsible for filtering metabolic wastes from the blood.
Flame cells are found in Platyhelminthes,Antennal glands are found in Crustaceans,and Kidneys are the primary excretory organs in vertebrates.

(C) . $Balanoglossus$.
During a field trip,a student observed a marine organism with a worm-like body. The cylindrical body of $Balanoglossus$ (a hemichordate) is distinctly divided into three parts: a proboscis,a collar,and a long trunk. Therefore,the organism is $Balanoglossus$.