Class - Cyclostomata Questions in English

(B) The animals belonging to the class $Cyclostomata$ are characterized by being jawless fishes.
These organisms have a sucking and circular mouth without jaws.
$Lampreys$ $(Petromyzon)$ and $Hagfishes$ $(Myxine)$ are the two primary examples of $Cyclostomata$ mentioned in the $NCERT$ textbook.
Therefore,the correct pair is $Lampreys$ and $Hagfishes$.

(C) The organism described is $Petromyzon$ (Lamprey).
$Petromyzon$ belongs to the class $Cyclostomata$,which are jawless vertebrates.
They are known for their unique life cycle: they migrate from the ocean to fresh water for spawning (anadromous migration).
After spawning,they die,and their larvae,after metamorphosis,return to the ocean.

(A) $Petromyzon$ (Lamprey) is a jawless fish belonging to the class $Cyclostomata$.
It exhibits anadromous migration,meaning it migrates from the ocean to freshwater for spawning.
After spawning,the adults die,and the larvae,known as $Ammocoetes$ larvae,undergo metamorphosis and eventually return to the ocean.

(D) $1$. Option $A$ is incorrect because crocodiles have a four-chambered heart.
$2$. Option $B$ is incorrect because cartilaginous fishes (Chondrichthyes) do not have an operculum.
$3$. Option $C$ is incorrect because some mammals like the platypus and echidna are oviparous.
$4$. Option $D$ is correct because members of the class Cyclostomata are characterized by the absence of jaws and paired fins.

(D) lamprey (sometimes also called as lamprey eel) is a jawless fish that belongs to the class $Cyclostomata$.
Lampreys possess a toothed,funnel-like sucking mouth and have scaleless,slimy skin with seven pairs of circular gill slits on each side.
They are well known as ectoparasites that bore into the flesh of other fish to suck their blood.
In contrast,Flying fox $(Pteropus)$,Hedgehog $(Erinaceus)$,and Manatee $(Trichechus)$ are all members of the class $Mammalia$.

(N/A) The characteristics of class $Cyclostomata$ are as follows:
$1$. All living members of the class $Cyclostomata$ are ectoparasites on some fishes.
$2$. They have an elongated body bearing $6-15$ pairs of gill slits for respiration.
$3$. $Cyclostomes$ have a sucking and circular mouth without jaws.
$4$. Their body is devoid of scales and paired fins.
$5$. The cranium and vertebral column are cartilaginous.
$6$. Circulation is of the closed type.
$7$. $Cyclostomes$ are marine but migrate for spawning to fresh water. After spawning,within a few days,they die. Their larvae,after metamorphosis,return to the ocean.

(N/A) $\rightarrow$ All living members of the class Cyclostomata are ectoparasites on some fishes.
$\rightarrow$ They have an elongated body bearing $6-15$ pairs of gill slits for respiration.
$\rightarrow$ Cyclostomes have a sucking and circular mouth without jaws.
$\rightarrow$ Their body is devoid of scales and paired fins.
$\rightarrow$ The cranium and vertebral column are cartilaginous.
$\rightarrow$ Circulation is of the closed type.
$\rightarrow$ Cyclostomes are marine but migrate for spawning to fresh water.
$\rightarrow$ After spawning,within a few days,they die.
$\rightarrow$ Their larvae,after metamorphosis,return to the ocean.
$\rightarrow$ Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

(A) $Petromyzon$ (lamprey) is a jawless vertebrate.
It belongs to the phylum $Chordata$,subphylum $Vertebrata$,and division $Agnatha$ (which includes jawless vertebrates).
Therefore,the correct classification for $Petromyzon$ is $Agnatha$.

(D) $Petromyzon$ is a jawless vertebrate belonging to the class $Cyclostomata$.
These organisms are characterized by having a circular,sucking mouth without jaws.
$Petromyzon$ is commonly known as the sea lamprey.

(B) According to the classification of sub-phylum $Vertebrata$ (Craniata),the sub-phylum is divided into two divisions based on the presence or absence of jaws:
$1$. $Agnatha$: These are jawless vertebrates. $Cyclostomata$ belongs to this division.
$2$. $Gnathostomata$: These are jawed vertebrates,which are further divided into superclasses $Pisces$ and $Tetrapoda$.
Therefore,$Cyclostomata$ belongs to the division $Agnatha$.

(A) $Myxine$ is a member of the class $Cyclostomata$.
According to the taxonomic hierarchy of Phylum $Chordata$:
$1$. Phylum $Chordata$ is divided into $Acraniata$ and $Craniata$.
$2$. $Myxine$ belongs to $Craniata$ (as it possesses a cranium).
$3$. Within $Craniata$,it falls under the division $Agnatha$ (jawless vertebrates).
$4$. Finally,it is classified under the class $Cyclostomata$.
Therefore,the correct hierarchical classification is $Chordata \rightarrow Craniata \rightarrow Agnatha \rightarrow Cyclostomata$.

(D) Lamprey $(Petromyzon)$ and Hagfish $(Myxine)$ both belong to the class $Cyclostomata$,which is part of the division $Agnatha$ and sub-phylum $Vertebrata$. These organisms are characterized by having a circular,sucking mouth and lacking jaws.

(D) $Agnatha$ are jawless vertebrates in which the notochord persists throughout life.
$Agnatha$ is divided into two classes: $Ostracodermi$ and $Cyclostomata$.
Examples of cyclostomes are Hagfish $(Myxine)$ and Lamprey $(Petromyzon)$.
$Agnatha$ members do not possess an exoskeleton and have a cartilaginous vertebral column.
Therefore,$Agnatha$ members lack a bony skeleton.

(A) Development is indirect in lamprey $(Petromyzon)$.
The larva of the lamprey is called the $Ammocoete$ larva.
The $Ammocoete$ larva is similar to the adult $Amphioxus$,hence the $Ammocoete$ larva acts as a connecting link between cephalochordates and cyclostomes.

(B) Lamprey $(Petromyzon)$ are marine organisms,but adult lampreys migrate to fresh water for spawning.
Such migration from the sea to a river for breeding is known as anadromous migration.

(C) The correct answer is $C$.
$Petromyzon$ (Lamprey) is a marine cyclostome that exhibits anadromous migration,meaning it migrates from the ocean to fresh water (rivers) for spawning.
After spawning,the adult lamprey dies within a few days and does not migrate back to the ocean.
The ammocoete larva,after metamorphosis,migrates from the river to the ocean.
$Petromyzon$ possesses a circular,suctorial mouth and acts as a sanguivorous (blood-sucking) ectoparasite on other fishes.

(N/A) $\rightarrow$ Cyclostomes are marine but migrate to fresh water for spawning.
$\rightarrow$ After spawning,they die within a few days.
$\rightarrow$ Their larvae,after metamorphosis,return to the ocean.
$\rightarrow$ Examples: $Petromyzon$ (Lamprey) and $Myxine$ (Hagfish).

(C) The group of chordates that possess a sucking and circular mouth without jaws is known as $Cyclostomata$.
$Cyclostomata$ are characterized by the absence of jaws (agnathans).
They have an elongated body bearing $6-15$ pairs of gill slits for respiration.
Their mouth is circular and suctorial,which helps them attach to other fishes as ectoparasites.

(A) Hagfish (class $Myxini$) are primitive jawless marine vertebrates. Unlike other vertebrates,they possess a variable number of gill slits depending on the species. The number of gill slits in hagfish typically ranges from $6$ to $15$ pairs. These slits are used for respiration and are a characteristic feature of their anatomy.

(B) The characteristics of Class $Cyclostomata$ are as follows:
$1$. They are ectoparasites on some fishes.
$2$. They have an elongated body bearing $6-15$ pairs of gill slits for respiration.
$3$. They have a sucking and circular mouth without jaws ($I$ is correct).
$4$. Their body is devoid of scales and paired fins ($II$ is correct).
$5$. Cranium and vertebral column are cartilaginous (not bony,so $III$ is incorrect).
$6$. Circulation is of closed type ($IV$ is correct).
$7$. Cyclostomes are marine but migrate for spawning to freshwater. After spawning,within a few days,they die. Their larvae,after metamorphosis,return to the ocean ($V$ is incorrect as it states they live in freshwater and spawn in the ocean,which is the reverse).
$8$. They show indirect development (larval stage is present,so $VI$ is incorrect).
Therefore,the correct statements are $I, II,$ and $IV$.

(C) Cyclostomes are a group of jawless vertebrates.
Statement $(a)$ is correct: They lack scales and paired fins.
Statement $(b)$ is incorrect: They have a circular mouth,but they are jawless (agnathans).
Statement $(c)$ is correct: They bear $6-15$ pairs of gill slits for respiration.
Statement $(d)$ is incorrect: Cyclostomes are marine but migrate to fresh water for spawning (anadromous migration),after which they die.
Therefore,statements $(b)$ and $(d)$ are incorrect.

(D) The class $Cyclostomata$ consists of jawless vertebrates.
All living members of this class are $Ectoparasites$ on some fishes.
They possess a circular,sucking mouth without jaws,which they use to attach to the body of host fishes to feed on their blood and flesh.
Therefore,the correct option is $D$.

(A) Cyclostomates (e.g.,Petromyzon or Lamprey) are marine organisms that exhibit anadromous migration.
They migrate from the ocean to fresh water specifically for the purpose of spawning (laying eggs).
After spawning,they die within a few days.
Their larvae,after undergoing metamorphosis,return to the ocean.
Since the migration to fresh water is directly linked to the spawning process mentioned in the reason,the reason provides a correct explanation for the assertion.

(C) The features mentioned (ventral muscular heart,kidneys for excretion/osmoregulation,and paired appendages) are characteristic of most Gnathostomes (jawed vertebrates).
$1$. $Labeo$ (a bony fish) possesses these features.
$2$. $Balaenoptera$ (a whale,mammal) possesses these features.
$3$. $Rana$ (a frog,amphibian) possesses these features.
$4$. $Petromyzon$ (a lamprey) belongs to the class Cyclostomata. Cyclostomes are jawless vertebrates $(Agnatha)$ and lack paired appendages (fins or limbs). Therefore,$Petromyzon$ is the exception.

(D) The class $Cyclostomata$ includes animals that are characterized by having a sucking and circular mouth without jaws.
These organisms are known as jawless fishes.
$Hagfish$ $(Myxine)$ and $Lamprey$ $(Petromyzon)$ are the primary examples of $Cyclostomata$.
Other options like $Magur$,$Flying$ $fish$,$Eel$,$Rohu$,and $Dog$ $fish$ belong to the classes $Chondrichthyes$ or $Osteichthyes$,which possess jaws.

(A) The class $Cyclostomata$ includes jawless vertebrates.
Key characteristics include:
$1$. They have an elongated body bearing $6-15$ pairs of gill slits for respiration.
$2$. They lack jaws (agnathans) and do not possess scales or paired fins.
$3$. Their body is devoid of scales and paired fins.
$4$. They are often ectoparasites on some fishes.
$5$. Their circulation is of the closed type.
$6$. They are marine but migrate for spawning to fresh water. After spawning,within a few days,they die. Their larvae,after metamorphosis,return to the ocean. Thus,the development is indirect.
Comparing the options,option $A$ correctly describes the key features: indirect development,$6-15$ pairs of gill slits,and ectoparasitic nature.

(A) Statement $- I$ is correct because all living members of the class $Cyclostomata$ are known to be ectoparasites on some fishes.
Statement $- II$ is correct because the name $Cyclostomata$ itself implies 'circular mouth' ($cyclo$ = circular,$stoma$ = mouth). They lack jaws (agnathans) and possess a sucking and circular mouth used for attachment to their hosts.

(C) The characters described are:
$1$. Endoskeleton is cartilaginous.
$2$. Ectoparasitic nature with a circular,suctorial mouth.
$3$. Absence of paired fins and scales.
$4$. Presence of $6-15$ pairs of gill slits for respiration.
These features are diagnostic of the class $Cyclostomata$. Among the given options,$Petromyzon$ (lamprey) belongs to this class. $Scoliodon$ is a cartilaginous fish (Chondrichthyes),$Exocoetus$ is a bony fish (Osteichthyes),and $Branchiostoma$ is a cephalochordate.