Phylum-Chordata Questions in English

(C) In animal development,the blastopore is the first opening formed during gastrulation.
If the blastopore develops into the anus and the mouth forms later as a secondary opening,the organism is classified as a $Deuterostome$.
This developmental pattern is characteristic of $Echinodermata$ and $Chordata$.
Conversely,in $Protostomes$,the blastopore develops into the mouth first.

(C) In echinoderms and chordates,the true coelom develops from an outgrowth of the enteron or embryonic gut,which is known as enterocoelom. This type of coelom formation is characteristic of deuterostomes.

(C) Metamerism is a condition in which the body is composed of a linear series of similar body segments called metameres or somites.
This phenomenon is a characteristic feature observed in the phyla $Annelida$,$Arthropoda$,and $Chordata$.
In $Chordata$,metamerism is primarily evident in the internal structures such as the vertebral column and the arrangement of muscles (myotomes).

(A) Chordates are defined by the presence of three fundamental characteristics at some stage of their life cycle: a notochord,a dorsal hollow nerve cord,and pharyngeal gill slits.
Non-chordates are animals that lack these three specific features.
Therefore,the absence of a notochord is a primary characteristic that distinguishes non-chordates from chordates.

(A) The enterocoelous coelom is formed by the outpocketing of the embryonic gut (archenteron).
This type of coelom formation is a characteristic feature of deuterostomes.
Deuterostomes include phyla such as Echinodermata,Hemichordata,and Chordata.
In these organisms,the blastopore of the gastrula develops into the anus,while the mouth is formed secondarily.

(D) The phylum $Chordata$ is divided into two groups: $Acrania$ $(Protochordata)$ and $Craniata$ $(Euchordata)$.
$Protochordates$ are primitive chordates that are classified based on the presence,absence,or extent of the $Notochord$ in their body.
They are further divided into three subphyla: $Hemichordata$,$Urochordata$,and $Cephalochordata$,all of which are defined by the characteristics and distribution of the $Notochord$.

(D) The correct answer is $D$.
$Amphioxus$ (also known as $Branchiostoma$ or lancelet) belongs to the subphylum $Cephalochordata$.
In $Cephalochordates$,the notochord persists throughout their life and is not replaced by a vertebral column.
Therefore,they are considered protochordates and not true vertebrates (subphylum $Vertebrata$).
$Oryctolagus$ (rabbit),$Eurotyphlis$ (a type of caecilian amphibian),and $Sparrow$ (bird) are all vertebrates.

(B) $Amphioxus$ $(Branchiostoma)$ belongs to the subphylum $Cephalochordata$. In this group,the notochord is present throughout the entire life and extends from the head to the tail region.

(B) $Branchiostoma$ (also known as $Amphioxus$ or lancelet) is a classic example of the subphylum $Cephalochordata$. In this group,the notochord extends from the head to the tail region and persists throughout their life.

(C) In $Tunicata$ (also known as $Urochordata$),the notochord is present only in the larval tail region and disappears in the adult stage.

(C) Retrogressive metamorphosis is a process in which a highly developed larva transforms into a simpler or less developed adult.
In $Herdmania$ (a Urochordate),the larva possesses a notochord,a dorsal hollow nerve cord,and a post-anal tail,which are characteristic features of chordates.
However,during metamorphosis,the larva undergoes degeneration,losing its tail,notochord,and most of its nervous system to become a sedentary,sac-like adult.
Therefore,$Herdmania$ is the classic example of retrogressive metamorphosis.

(D) Chordates are characterized by the presence of a dorsal,hollow,and tubular nerve cord.
In contrast,non-chordates typically possess a ventral,solid nerve cord.
The nerve cord in chordates lies dorsal to the notochord and extends along the length of the body.

(B) The phylum $Chordata$ is characterized by the presence of a notochord,a dorsal hollow (tubular) nerve cord,and paired pharyngeal gill slits at some stage of their life cycle.
In contrast to non-chordates,which typically possess a solid ventral nerve cord,chordates possess a dorsal,hollow,and tubular nerve cord that develops from the ectoderm.

(C) The correct answer is $C$. $A$ post-anal tail is a characteristic feature of chordates,which is present at least during the embryonic stage of their life cycle.
In non-chordates,the body is either not extended beyond the anus or the tail is not post-anal.
In many chordates,the post-anal tail helps in balance and locomotion.
It also provides protection to the genital and anal regions.

(B) . $Amphioxus$ (commonly known as $Lancet$) possesses a wheel organ,also called a rotatory organ or $Muller's$ organ,in the oral hood. It creates a whirling water current to sweep food organisms into the mouth.

(D) The correct answer is $D$.
$Sea$ $squirt$ (also known as $Herdmania$) belongs to the subphylum $Urochordata$ (or $Tunicata$).
In $Urochordates$,the notochord is present only in the larval tail and is replaced or lost in the adult stage.
Since they do not possess a vertebral column,they are classified as protochordates (invertebrate chordates) rather than vertebrates.

(A) The phylum $Chordata$ is characterized by the presence of a $notochord$ (also known as $chorda$ $dorsalis$),a dorsal hollow nerve cord,and paired pharyngeal gill slits at some stage of their life cycle.
$Chorda$ $dorsalis$ is the defining feature that distinguishes chordates from non-chordates.

(B) The subphylum $Vertebrata$ is characterized by the presence of a notochord during the embryonic period,which is replaced by a cartilaginous or bony vertebral column in the adult.
Additionally,all vertebrates possess a well-developed cranium (skull) that encloses the brain.
While other features like appendages or specific body divisions may vary or be absent in certain groups (e.g.,snakes lack appendages),the presence of a cranium is a diagnostic feature of all vertebrates.

(B) The group of animals possessing a cranium,vertebral column,ventral heart,and pulmonary respiration is classified under the subphylum $Vertebrata$.
Within $Vertebrata$,the superclass $Tetrapoda$ is specifically defined by the presence of two pairs of limbs (pentadactyl limbs).
While $Vertebrata$ includes all animals with a cranium and vertebral column,$Tetrapoda$ is a more specific (smaller) taxonomic group that includes amphibians,reptiles,birds,and mammals,all of which possess two pairs of limbs.
Therefore,$Tetrapoda$ is the smallest taxonomic group among the options that satisfies all the given criteria.

(C) In $Urochordata$ (also known as $Tunicata$),the notochord is present only in the tail region of the free-swimming tadpole-like larva. It disappears in the adult stage,which is typically sessile.

(A) $Herdmania$ belongs to the subphylum $Urochordata$,where the notochord is present only in the larval tail and disappears in the adult stage.
$Balanoglossus$ belongs to the phylum $Hemichordata$,which was earlier considered a subphylum of $Chordata$ but is now classified as a separate phylum because it lacks a true notochord.
Therefore,in adult $Herdmania$ and $Balanoglossus$,the notochord is absent.

(D) The fundamental characteristics of the phylum $Chordata$ include the presence of a notochord,a dorsal hollow nerve cord,and paired pharyngeal gill slits at some stage of their life cycle.
$A$,$B$,and $C$ are the primary diagnostic features of chordates.
$D$ (presence of a spinal cord) is a specialized feature found only in vertebrates,which is a subphylum of $Chordata$. Therefore,it is not a fundamental characteristic of all chordates.

(C) The correct answer is $C$.
Tunicates (Urochordates) are primarily ciliary or filter feeders.
They obtain their food by filtering microscopic organisms such as diatoms,desmids,and protozoans suspended in seawater.
This process is facilitated by the movement of cilia located in the pharyngeal region,which creates a water current to trap food particles.

(A) $Amphioxus$ (Cephalochordata),frog (Amphibia),sea horse (Osteichthyes),and crocodile (Reptilia) all belong to the phylum $Chordata$.
All chordates possess three fundamental characteristics at some stage of their life cycle: a notochord,a dorsal hollow nerve cord,and pharyngeal gill slits.
Therefore,the presence of pharyngeal gill slits,at least during developmental stages,is the common feature among these organisms.

(B) The fundamental characteristics of the phylum $Chordata$ include the presence of a notochord,a dorsal hollow nerve cord,and paired pharyngeal gill-slits at some stage of their life cycle.
While not all chordates possess a vertebral column (e.g.,$Urochordata$ and $Cephalochordata$),all chordates exhibit pharyngeal gill-slits at some point during their development.
Therefore,the presence of pharyngeal gill-slits is a diagnostic feature common to all chordates.

(C) $Herdmania$ is a marine chordate commonly known as a sea squirt.
It belongs to the subphylum $Urochordata$ (also known as $Tunicata$).
In $Urochordata$,the notochord is present only in the larval tail and disappears in the adult stage.

(C) The phylum $Chordata$ is primarily characterized by the presence of a notochord at some stage in their life cycle.
While the vertebral column is a feature of $Vertebrata$ (a subphylum of $Chordata$),the notochord is the fundamental diagnostic feature that defines the entire phylum $Chordata$.

(D) Fish are aquatic vertebrates that belong to the class $Pisces$. They respire through $Gills$ throughout their life cycle.
Whales are aquatic mammals that belong to the class $Mammalia$. They breathe through $Lungs$ and possess $Blubber$ (a thick layer of fat) for insulation.
Therefore,the primary anatomical difference regarding respiration is that fish possess $Gills$,whereas whales possess $Lungs$.

(A) The post-anal tail is a characteristic feature of the phylum $Chordata$.
Among the given options,$Cobra$ belongs to the class $Reptilia$,which is a sub-group of the phylum $Chordata$.
$Earthworm$ belongs to the phylum $Annelida$,$Scorpion$ belongs to the phylum $Arthropoda$,and lower invertebrates do not possess a post-anal tail.
Therefore,the correct answer is $Cobra$.

(C) $Archaeopteryx$ is a transitional fossil between non-avian dinosaurs and modern birds. Unlike modern birds,which have a keratinous beak without teeth,$Archaeopteryx$ possessed jaws equipped with sharp teeth,which is a reptilian characteristic.

(B) The fundamental characteristics of the phylum $Chordata$ include the presence of a $notochord$, a $dorsal$ $tubular$ $nervous$ $system$ (nerve cord), and $pharyngeal$ $gill$ $slits$ at some stage of their life cycle. These features are diagnostic for all chordates.

(B) Gnathostomata is a division of the subphylum Vertebrata characterized by the presence of jaws. Based on the type of locomotory organs,Gnathostomata is divided into two superclasses:
$1$. Pisces: These are aquatic vertebrates that use fins for locomotion.
$2$. Tetrapoda: These are terrestrial vertebrates that use limbs for locomotion.

(D) The group $Amniota$ is characterized by the presence of an $amnion$, a protective membrane that surrounds the embryo during development.
This group includes $Reptiles$, $Birds$, and $Mammals$.
These organisms are collectively known as $Amniotes$ because they produce an $amniotic$ egg or develop an $amnion$ in the uterus, which allows them to reproduce in terrestrial environments.

(B) The correct answer is $B$.
Tunicates (Urochordates),such as $Herdmania$,exhibit a phenomenon known as retrogressive metamorphosis.
In this process,the free-swimming larva possesses a well-developed notochord and a dorsal nerve cord.
However,during metamorphosis into the adult stage,these chordate characteristics degenerate,and the adult becomes a sessile,sac-like organism.

(D) Both the rabbit ($Oryctolagus$ $cuniculus$) and the frog ($Rana$ $tigrina$) belong to the phylum $Chordata$.
One of the fundamental characteristics of all chordates is the presence of a $dorsal$ $tubular$ $nerve$ $cord$ at some stage of their life cycle.
Therefore,the presence of a dorsal tubular nerve cord is a common feature shared by both organisms.

(D) The correct answer is $D$.
Haemoglobin is an iron-containing respiratory pigment found in the red blood cells of vertebrates.
It is a conjugated protein that binds with oxygen to form oxyhaemoglobin,which gives the blood its characteristic red color.
Myoglobin is found in muscle tissues,while anthocyanins are plant pigments.

(C) The respiratory pigment containing vanadium,known as vanabins,is found in the blood cells of ascidians (tunicates). These organisms belong to the subphylum Tunicata (Urochordata) and are known for their unique ability to accumulate vanadium from seawater.

(D) The cloaca is a common chamber found in many vertebrates,including birds,reptiles,amphibians,and some fish. It serves as the single opening for the digestive,reproductive,and urinary tracts. Therefore,the rectum (digestive tract),the reproductive tract,and the urinary tract all empty into the cloaca.

(A) In vertebrates,the embryonic notochord is replaced by the vertebral column (also known as the backbone or spine).
This structure provides support and protection for the spinal cord.
Therefore,the correct option is $A$.

(D) The process of formation of the notochord,which serves as the primary skeletal rod in the early embryo of chordates,is specifically termed as $Notogenesis$.
Neurulation refers to the formation of the neural tube.
Blastulation is the process of formation of the blastula.
Morulation is the process of formation of the morula.

(C) The alimentary canal,including the intestine,is derived from the endoderm germ layer in both chordates and non-chordates. During embryonic development,the endoderm forms the epithelial lining of the digestive tract.

(B) closed circulatory system is one where blood is confined within vessels (arteries,veins,and capillaries).
Among the given options,$A$,$C$,and $D$ (Cockroach,Mosquito,and Housefly) are arthropods,which possess an open circulatory system where blood flows into body cavities called sinuses.
$B$ (Tadpole/Fish) belongs to the phylum Chordata,which is characterized by a closed circulatory system where blood is pumped by the heart through a network of closed vessels.

(D) The presence of a $post-anal tail$ is one of the fundamental diagnostic characteristics of the phylum $Chordata$.
Among the given options, $Earthworm$ $(Annelida)$, $Scorpion$ $(Arthropoda)$, and $Lower invertebrates$ do not possess a post-anal tail.
$Snake$ belongs to the class $Reptilia$ under the phylum $Chordata$.
Therefore, a snake possesses a post-anal tail during its life cycle.

(D) Vertebrates are a subphylum of the phylum $Chordata$. Their primary characteristics include:
$1$. $A$ dorsal hollow nerve cord.
$2$. $A$ ventral heart.
$3$. $A$ body cavity (coelom) with a complete digestive tract.
Since all these features are characteristic of vertebrates,the correct option is $D$.

(D) The phylum $Chordata$ is characterized by the presence of three fundamental features at some stage of their life cycle:
$1$. $Notochord$: $A$ flexible, rod-like structure providing support.
$2$. $Dorsal$ $hollow$ $nerve$ $cord$: $A$ nerve cord located dorsally to the notochord.
$3$. $Pharyngeal$ $gill$ $slits$: Openings in the pharyngeal region.
Since all three features are characteristic of chordates, the correct answer is $D$.

(A) The phylum Chordata is divided into three subphyla: Urochordata (Tunicata),Cephalochordata,and Vertebrata.
$1$. Urochordata (Tunicata) includes animals like $Herdmania$,$Salpa$,and $Doliolum$,where the notochord is present only in the larval tail.
$2$. $Balanoglossus$ belongs to the phylum Hemichordata.
$3$. $Amphioxus$ $(Branchiostoma)$ belongs to the subphylum Cephalochordata,where the notochord extends from head to tail region and is persistent throughout their life.
$4$. $Petromyzon$ belongs to the class Cyclostomata under the subphylum Vertebrata.
Therefore,the correct option is $A$.

(C) Metamerism or metameric segmentation is a characteristic feature where the body is divided into repeating units or segments. In chordates,this is primarily observed in the arrangement of muscles (myotomes),vertebrae,and nerves. Even though it may not be externally visible in all adult chordates,it is present during embryonic development in all members of the phylum $Chordata$. Therefore,the statement is applicable to all chordates because they exhibit some form of serial repetition of body parts during some stage of their development.

(A) In the phylum $Chordata$,the subphylum $Cephalochordata$ is characterized by the presence of a notochord that extends from the head to the tail region and persists throughout their life.
$Branchiostoma$ (also known as $Amphioxus$ or $Lancelet$) is a classic example of $Cephalochordata$.
In $Herdmania$ (a $Urochordate$),the notochord is present only in the larval tail.
$Balanoglossus$ belongs to the phylum $Hemichordata$,where the notochord is absent (it has a stomochord).
$Frog$ is a $Vertebrate$ where the notochord is replaced by a vertebral column in the adult stage.
Therefore,the correct answer is $Branchiostoma$.

(B) The $rotatory$ $organ$,also known as the $wheel$ $organ$ or $Muller's$ $organ$,is a characteristic feature found in the pharynx of $Amphioxus$ (also known as $Branchiostoma$ or $Lancelet$).
It is a ciliated structure that helps in creating water currents for filter feeding.
Therefore,the correct option is $B$.

(D) Cephalochordates (e.g.,$Branchiostoma$ or $Amphioxus$) exhibit the following characteristics:
$1$. They are exclusively marine organisms.
$2$. They retain all three primary chordate characteristics (notochord,dorsal hollow nerve cord,and pharyngeal gill slits) throughout their entire life cycle.
$3$. They are ciliary feeders,meaning they use cilia to create water currents to bring food particles into their pharynx.
Therefore,all the given statements are correct.