Class-Amphibia Questions in English

(C) The order $Anura$ includes common amphibians like frogs and toads. In their life cycle,the larval stage,known as the tadpole,possesses a tail and gills for aquatic respiration. As they undergo metamorphosis to become adults,they lose their tail and develop lungs.

(B) The class $Amphibia$ is divided into three living orders:
$1$. $Anura$ (or $Salientia$): This order includes frogs and toads. They are tailless in their adult stage.
$2$. $Urodela$ (or $Caudata$): This order includes salamanders and newts,which possess tails throughout their life.
$3$. $Apoda$ (or $Gymnophiona$): This order includes limbless amphibians like $Ichthyophis$.
Therefore,frogs and toads belong to the order $Anura$.

(A) The order $Anura$ (also known as $Salientia$) consists of amphibians that lack a tail in their adult stage.
The term $Anura$ is derived from the Greek words '$A$' (meaning absent) and '$ura$' (meaning tail).
Examples include frogs and toads.
In contrast,$Urodela$ $(Caudata)$ possess tails,and $Gymnophiona$ $(Apoda)$ are limbless amphibians.

(B) The correct answer is $B$.
$A$ Frog,$C$ Salamander,and $D$ Toad are all members of the class $Amphibia$.
$B$ Tortoise is a reptile belonging to the order $Chelonia$ (or $Testudines$). Reptiles are characterized by dry,cornified skin and epidermal scales,which distinguishes them from amphibians.

(D) $Necturus$ is commonly known as the Mud puppy. It is an aquatic salamander belonging to the family $Proteidae$, characterized by the retention of external gills throughout its adult life (neoteny). It is primarily found in North America.

(B) The correct answer is $B$.
Salamander belongs to the class $Amphibia$.
These organisms are characterized by their ability to live in both aquatic and terrestrial habitats.
They are cold-blooded,have moist skin without scales,and typically undergo metamorphosis during their life cycle.

(A) The Midwife toad, scientifically known as $Alytes \text{ } obstetricans$, is a species of toad found in Europe. It is called the 'Midwife toad' because the male carries the fertilized eggs wrapped around his hind legs until they are ready to hatch, effectively acting as a 'midwife' for the developing embryos.

(B) Amphibians are unique vertebrates that typically require a moist environment for their life cycle.
Most amphibians lay their eggs in water or very moist environments because their eggs lack a protective shell and would dry out on land.
Therefore,water is essential for their reproduction and the development of their larval stages.

(A) The ability of amphibians to change their body color through the expansion and contraction of pigment cells (chromatophores) is known as metachrosis.

(A) $Rhacophorus$ is commonly known as the flying frog.
It possesses characteristic large webs developed between its elongated digits.
These webs,along with its flattened body,act like a parachute,allowing the frog to glide from higher elevations to lower ones.
Therefore,they are designated as 'flying frogs'.

(C) $Hyla$ is commonly known as the tree frog. It belongs to the class $Amphibia$ and is adapted for an arboreal (tree-dwelling) lifestyle,possessing adhesive discs on its digits to help it climb.

(A) The class $Amphibia$ is characterized by animals that possess two pairs of pentadactyl limbs,which are adapted for locomotion such as walking and swimming.
In most amphibians,the forelimbs typically end in four digits,while the hind limbs possess five digits.
$A$ key diagnostic feature of this class is that these digits lack claws or nails,distinguishing them from reptiles,birds,and mammals.

(C) The absence of a thumb is a characteristic feature of the $Frog$ (Amphibians).
In $Frog$ forelimbs, there are four digits, and the thumb (pollex) is absent or vestigial.
In contrast, $Rabbit$, $Man$, and $Monkey$ are mammals that possess a thumb or a digit that functions as a thumb.

(D) $Bombinator$ is a small-sized amphibian found in Europe.
It is commonly known as the Fire-bellied toad.

(A) The common Indian bullfrog is scientifically known as $Rana \ tigrina$.
It belongs to the class $Amphibia$ and is widely distributed across the Indian subcontinent.
$Rana \ esculenta$ is the edible frog,$Rana \ silvatica$ is the wood frog,and $Rana \ cyanophlyctis$ is the skittering frog.

(C) The phenomenon where an organism retains its larval or juvenile characteristics even after reaching sexual maturity is known as $Neoteny$. This is commonly observed in certain amphibians like the axolotl.

(B) $Ambystoma$ is a genus of mole salamanders. The larva of $Ambystoma$ is known as an axolotl. It is primarily found in $Mexico$. $A$ unique feature of the axolotl is that it exhibits neoteny (or paedogenesis),meaning it retains its larval features,such as external gills,even after reaching sexual maturity.

(A) The $Axolotl$ is the larval stage of the Mexican salamander, $Ambystoma$ $\text{mexicanum}$.
Salamanders belong to the class $Amphibia$ and the order $Urodela$ (also known as $Caudata$), which is characterized by the presence of a tail in both larval and adult stages.
Therefore, the correct order is $Urodela$.

(D) $Caecilians$ are limbless amphibians that belong to the order $Gymnophiona$ (also known as $Apoda$).
These organisms are characterized by their worm-like appearance and are sometimes referred to as blindworms.

(A) $Pipa \text{ } americana$ is commonly known as the Surinam toad. It belongs to the family Pipidae and is well-known for its unique reproductive behavior where the eggs are embedded in the skin of the female's back.

(C) Amphibians are classified into three living orders: $Anura$ (frogs and toads),$Urodela$ (salamanders and newts),and $Gymnophiona$ (caecilians).
$Gymnophiona$ (also known as $Apoda$) consists of limbless,worm-like amphibians that are typically burrowing or aquatic.
Therefore,limbless amphibians belong to the order $Gymnophiona$.

(B) $Ichthyophis$ is a limbless amphibian belonging to the order $Gymnophiona$ (or $Apoda$).
It is known for exhibiting parental care and typically lacks a tongue.

(D) The term $Amphibia$ is derived from the Greek words $amphi$ (meaning 'both') and $bios$ (meaning 'life').
Amphibians are vertebrates that can live in both aquatic and terrestrial habitats.
While adult frogs are capable of living on land,they require water for reproduction,as their eggs lack a protective shell and would desiccate on land.
Furthermore,the larval stage of the frog,known as the $tadpole$,is strictly aquatic and breathes through gills,which is a defining characteristic of their dual-life cycle.

(A) Amniotes are vertebrates that possess an amnion,a protective membrane surrounding the embryo.
Reptiles,Aves (birds),and Mammals are classified as amniotes because their embryos develop within an amnion.
Amphibians are classified as anamniotes because they lack an amnion and typically lay their eggs in water or moist environments.

(D) The amphibian heart is three-chambered,consisting of two auricles and one ventricle.
It receives oxygenated (arterial) blood from the lungs/skin into the left auricle and deoxygenated (venous) blood from the rest of the body into the right auricle.
Both types of blood mix in the single ventricle before being pumped out.
Therefore,the heart handles both arterial and venous blood circulation.

(B) The order Gymnophiona $(Apoda)$ consists of limbless amphibians that often possess dermal scales embedded in their skin and exhibit distinct transverse wrinkles or annuli. In contrast,members of the order Urodela (such as salamanders and newts) typically possess smooth,moist skin without scales or transverse wrinkles. Therefore,the presence of smooth,moist skin is a characteristic feature distinguishing Urodela from many Gymnophiona.

(A) Frogs and toads belong to the order $Anura$.
$Anura$ is characterized by the absence of a tail in the adult stage.
They are also known as $Salientia$,which refers to their ability to leap or jump.

(C) The scientific name of the common toad is $Bufo \ melanostictus$.
$Hyla \ arborea$ is the tree frog.
$Xenopus \ laevis$ is the African clawed frog.
$Bombinator \ igneus$ is the fire-bellied toad.

(D) Toads and frogs belong to the order $Anura$.
Toads (family $Bufonidae$) differ from true frogs (family $Ranidae$) in several morphological and physiological aspects:
$1$. $Parotid$ $glands$: Toads possess large,prominent $parotid$ $glands$ behind their eyes that secrete toxins,which are absent in true frogs.
$2$. $Nocturnal$ $habit$: While many frogs are nocturnal,toads are predominantly $nocturnal$ and terrestrial.
$3$. $Absence$ $of$ $teeth$: True frogs typically have maxillary and vomerine teeth,whereas most toads are $edentulous$ (lack teeth).
Therefore,all the listed characteristics distinguish a toad from a frog.

(A) In $Rana$ (frog),the digestive tract,urinary tract,and reproductive tract open into a common chamber called the cloaca. The cloaca opens to the exterior through a single opening known as the cloacal aperture. In contrast,mammals like rabbits have separate openings for the anus and the urogenital tract. $Nereis$ and $Pheretima$ are annelids and do not possess a cloaca.

(C) The $RBCs$ (Red Blood Cells) of a frog are nucleated,oval,and biconvex in shape.
They contain haemoglobin,which acts as a respiratory pigment for oxygen transport.
In contrast,mature $RBCs$ in mammals (like rats,cats,and rabbits) are enucleated (lack a nucleus) to provide more space for haemoglobin.

(B) The heart of an amphibian is a $3$-chambered structure,consisting of two upper atria (auricles) and a single lower ventricle. This allows for the mixing of oxygenated and deoxygenated blood within the ventricle.

(C) The hormone $Thyroxine$ is essential for the metamorphosis of amphibian tadpoles into adult frogs.
Iodine is a key component required for the synthesis of $Thyroxine$.
When there is a deficiency of iodine,the production of $Thyroxine$ is inhibited.
Consequently,the metamorphosis process is halted or inhibited,and the tadpole continues to live in its larval stage without transforming into an adult frog.

(B) The heart of amphibians is $3$-chambered.
It consists of two auricles (atria) and one single ventricle.
This structure allows for the mixing of oxygenated and deoxygenated blood within the ventricle before it is pumped out to the body.

(D) The spiral valve is a specialized structure found within the $Truncus$ $arteriosus$ of the amphibian heart.
It plays a crucial role in directing the flow of oxygenated and deoxygenated blood into the appropriate aortic arches,thereby minimizing the mixing of blood.

(B) Amphibians possess mesonephric kidneys during their adult stage.
Pronephric kidneys are typically found in the embryos of amphibians and in some primitive fishes.
Metanephric kidneys are characteristic of higher vertebrates like reptiles,birds,and mammals.
Therefore,the correct type of kidney found in adult amphibians is mesonephric.

(B) The $Mentomeckelian$ bone is a small, specialized bone found in the lower jaw of amphibians, including $Rana \text{ } tigrina$ (the Indian bullfrog).
It is formed at the anterior end of $Meckel's \text{ } cartilage$, which serves as the embryonic scaffold for the lower jaw in vertebrates.
In adult frogs, this bone ossifies and becomes a distinct part of the mandible, making it a characteristic feature of the amphibian skull.

(C) The skull of an amphibian (like a frog) is dicondyllic,meaning it has two occipital condyles that articulate with the first vertebra (atlas).
Furthermore,amphibians possess $10$ pairs of cranial nerves.
Therefore,the correct answer is Amphibia.

(B) The lateral line system is a sensory organ found in aquatic vertebrates,including larval amphibians (tadpoles),which detects movement and vibration in water. As amphibians undergo metamorphosis to transition from an aquatic larval stage to a terrestrial adult stage,they lose the lateral line system. This loss is primarily an adaptation to their evolution of a terrestrial habit,as the lateral line system is ineffective in air.

(A) The $Amnion$ is an extra-embryonic membrane that provides protection against mechanical shock and desiccation (drying out) for the developing embryo.
Since amphibians lay their eggs in water,the surrounding water medium naturally provides protection against desiccation and mechanical stress.
Therefore,the evolutionary development of the $Amnion$ is not required in amphibians,making them $Anamniotes$.

(B) three-chambered heart consists of two atria and one ventricle.
This type of heart is characteristic of amphibians and most reptiles.
Among the given options,the frog is an amphibian.
Fish have a two-chambered heart,while rabbits and humans (mammals) have a four-chambered heart.

(C) The heart of a frog is $3$-chambered,consisting of two atria and one ventricle.
In the ventricle,oxygenated blood (from the left atrium) and deoxygenated blood (from the right atrium) mix together before being pumped out to the body and lungs.
Sharks have a $2$-chambered heart where only deoxygenated blood flows.
Rabbits have a $4$-chambered heart,which completely prevents the mixing of oxygenated and deoxygenated blood.
Therefore,the maximum mixing occurs in the $3$-chambered heart of the frog.

(B) The class $Amphibia$ is divided into three living orders: $Anura$ (or $Salientia$),$Urodela$ (or $Caudata$),and $Apoda$ (or $Gymnophiona$).
$Anura$ is the order that includes frogs and toads.
$Urodela$ includes salamanders and newts.
$Apoda$ (or $Gymnophiona$) includes limbless amphibians like caecilians.

(D) Amphibians possess moist,glandular skin that is highly vascularized.
This allows for cutaneous respiration,where gas exchange occurs directly through the skin.
Additionally,the skin acts as a barrier for protection against pathogens and physical damage.
It also plays a role in thermoregulation by facilitating heat loss or gain through evaporation and blood flow regulation.
Therefore,all the listed functions are performed by the skin of an amphibian.

(A) Ichthyophis is a limbless amphibian,commonly known as a caecilian. It belongs to the class $Amphibia$ and the order $Gymnophiona$ (or $Apoda$). These organisms are characterized by their worm-like appearance,which often leads to confusion with annelids or snakes,but they possess the diagnostic features of amphibians such as moist skin and a three-chambered heart.

(B) Amphibians belong to the class $Amphibia$ in the kingdom $Animalia$.
They are cold-blooded animals,which means they cannot regulate their internal body temperature according to the environment.
This condition is scientifically known as $Poikilothermic$ or ectothermic.
Therefore,the correct option is $B$.

(C) Amphibians have a $3$-chambered heart. It consists of two atria (auricles) that receive deoxygenated blood from the body and oxygenated blood from the lungs/skin,and one single ventricle that pumps the mixed blood out to the rest of the body. Therefore,the correct structure is two atria and one ventricle.

(C) Amphibians are a class of vertebrates that can live in both aquatic and terrestrial habitats.
Key diagnostic features include:
$1$. The skin is moist,smooth,and glandular,and it lacks scales.
$2$. They are poikilothermic (cold-blooded).
$3$. They typically have two pairs of limbs.
$4$. The heart is three-chambered.
$5$. Respiration occurs through lungs,skin,or buccal cavity.
Therefore,the absence of scales and the presence of moist,glandular skin is a primary characteristic feature used to identify amphibians.

(A) Amphibians are animals that belong to the class $Amphibia$.
Most amphibians are $oviparous$, meaning they lay eggs.
These eggs are typically laid in water or moist environments and are fertilized externally.
Therefore, the correct classification for amphibians regarding their reproductive mode is $oviparous$.

(D) In mammals,including humans,rabbits,and rats,mature $RBCs$ (erythrocytes) are enucleated (lack a nucleus) to provide more space for hemoglobin.
In contrast,amphibians like frogs possess nucleated $RBCs$ throughout their life cycle.
Therefore,the correct answer is $D$.