Anatomy of frog Questions in English

(B) In a frog,the oxygenated blood from the two lungs is collected by the right and left pulmonary veins. These veins unite to form a common pulmonary vein,which opens directly into the left auricle of the heart. Therefore,the pulmonary vein carries oxygenated blood.

(B) In frogs,respiration takes place through the skin,lungs,and buccopharyngeal cavity. To perform cutaneous (skin) respiration,the skin must remain moist due to the presence of mucous-secreting glands.

(D) In the frog's heart, a number of muscular ridges called $Columnae \text{ } carneae$ project from the wall of the ventricle into its cavity.
These ridges divide the peripheral part of the ventricular cavity into a number of small pockets.
They prevent the suction effect that would occur with a flat-surfaced membrane, thereby ensuring the heart pumps blood efficiently.

(A) Frogs do not drink water through their mouth. Instead,they absorb water directly from the environment through their skin. The skin of a frog is highly vascular and permeable,which allows for both cutaneous respiration and the absorption of water to maintain hydration.

(A) The correct matches are as follows:
$A$. Aquatic respiratory organ: $I$. Skin (Frogs respire through skin in water).
$B$. Organ which acts as urogenital duct: $II$. Ureter (In male frogs,the ureters act as urinogenital ducts).
$C$. $A$ small median chamber: $III$. Cloaca (It is a common chamber for the digestive,urinary,and reproductive tracts).
$D$. $A$ triangular structure: $IV$. Sinus venosus (It is a triangular chamber that joins the right atrium).
Therefore,the correct sequence is $A-I, B-II, C-III, D-IV$.

(A) When a bone is kept in dilute hydrochloric acid $(HCl)$ for several hours,the inorganic components of the bone matrix,such as calcium,magnesium,and potassium salts,are dissolved by the acid. The organic part of the bone,primarily collagen,remains intact. As a result of the removal of the mineral salts that provide rigidity,the bone loses its hardness and becomes flexible.

(C) In a frog,the heart pumps blood to the lungs and skin for oxygenation. The $pulmocutaneous$ $artery$ is responsible for carrying deoxygenated blood from the heart to the lungs and the skin,where gas exchange occurs. Therefore,it contains deoxygenated blood.

(B) The parasphenoid bone is a flattened and inverted $T-$shaped bone,which forms the floor (base) of the cranium in frogs.

(C) The zygomatic arch is a bony bridge in the skull of mammals.
In a rabbit,it is formed by the union of the zygomatic process of the maxilla,the jugal bone,and the zygomatic process of the squamosal bone.
These bones articulate to provide structural support to the cheek region and serve as an attachment site for masseter muscles.

(D) Frogs possess specialized pigment-containing cells in their skin known as chromatophores,which include melanophores,iridophores,and xanthophores.
These chromatophores are regulated by both the central nervous system and various hormones (such as melanocyte-stimulating hormone).
By adjusting the distribution of pigments within these cells,frogs can change their skin color to match their environment,producing a wide variety of shades ranging from brown to gray and green.

(A) The correct answer is $A$. Frogs are amphibians and typically inhabit freshwater environments. They cannot survive in saltwater (marine) environments because they lack the physiological adaptations to regulate osmotic pressure in high-salinity water.
$B$ is correct: The common Indian bullfrog is scientifically known as $Rana$ $tigrina$.
$C$ is correct: Frogs are poikilothermic,meaning their body temperature fluctuates with the ambient temperature.
$D$ is correct: During winter,they undergo hibernation (winter sleep) and during summer,they undergo aestivation (summer sleep) to avoid extreme temperatures.

(A) Frogs are carnivorous animals that feed on insects.
Since meat is easier to digest than plant cellulose,the alimentary canal of a carnivore is shorter compared to that of a herbivore.
Therefore,because frogs are carnivorous,their alimentary canal is short.

(A) In frogs, respiration occurs through different methods depending on the environment and activity level:
$1$. When the frog is on land, it primarily uses pulmonary respiration (lungs) $(II)$ and can also use buccopharyngeal respiration $(III)$ and cutaneous respiration $(I)$.
$2$. When the frog is in water, it primarily uses cutaneous respiration $(I)$ because the skin is moist and permeable to gases.
$3$. During aestivation (summer sleep) and hibernation (winter sleep), the metabolic rate is low, and the frog relies exclusively on cutaneous respiration $(I)$.
Therefore, the correct matching is: $P - (I, II, III)$, $Q - (I)$, $R - (I)$.

(B) $1$. Frog erythrocytes (red blood cells) are nucleated,which is a correct statement.
$2$. Human erythrocytes are enucleated (lack a nucleus) at maturity to provide more space for hemoglobin,making option $B$ incorrect.
$3$. Humans possess a closed circulatory system but lack a renal portal system,which is a correct statement.
$4$. Frogs possess a well-developed renal portal system,which is a correct statement.
Therefore,the incorrect statement is $B$.

(A) The heart of a frog is a $3$-chambered structure consisting of two atria and one ventricle.
It is covered by a membrane called the pericardium.
$A$ triangular structure called the sinus venosus joins the right atrium on the dorsal side.
It receives blood through the major veins called venae cavae.
Therefore,the sinus venosus opens into the right atrium.

(A) The heart of a frog is $3$-chambered,consisting of two atria and one ventricle.
Deoxygenated blood from the body is received by the right atrium,while oxygenated blood from the lungs and skin is received by the left atrium.
Both atria empty their contents into the single ventricle.
Consequently,the ventricle contains mixed blood,which is then pumped to the rest of the body.
Therefore,only $1$ chamber (the ventricle) contains mixed blood.

(A) In the excretory system of frogs, in male frogs, the ureter and vas deferens join to form a 'urinogenital duct' that opens into the cloaca. In female frogs, the ureter and oviduct open separately into the cloaca; therefore, there is no urinogenital duct in females. Thus, option $A$ is the incorrect statement.

(B) The nervous system of a frog is organized into the Central Nervous System $(CNS)$ and the Peripheral Nervous System $(PNS)$.
The $CNS$ includes the brain and the spinal cord.
The $PNS$ consists of the cranial nerves (arising from the brain) and the spinal nerves (arising from the spinal cord).
Therefore,option $B$ correctly describes this organization.

(A) In a frog $(Rana \, tigrina)$, the brain is enclosed in a bony brain box or cranium.
From the brain of a frog, $10$ pairs of cranial nerves arise.
These nerves are responsible for transmitting sensory and motor signals between the brain and various parts of the head and neck region.
Therefore, the correct answer is $10$ pairs.

(D) The brain of a frog is divided into three main parts:
$1$. Forebrain: It consists of paired cerebral hemispheres and the diencephalon. Thus,$P$ matches with $III$.
$2$. Midbrain: It is characterized by a pair of optic lobes. Thus,$Q$ matches with $I$.
$3$. Hindbrain: It consists of the cerebellum and the medulla oblongata. Thus,$R$ matches with $II$.
Therefore,the correct matching is $(P - III), (Q - I), (R - II)$.

(C) The given figure represents the female reproductive system of a frog.
In the female reproductive system of a frog:
$P$ represents the Oviduct,which is a coiled tube that transports eggs.
$Q$ represents the Ureter,which carries urine from the kidneys to the cloaca.
$R$ represents the Cloaca,which is a common chamber for the urinary,reproductive,and digestive tracts.
Therefore,the correct identification is $P$ = Oviduct,$Q$ = Ureter,and $R$ = Cloaca.

(A) In male frogs,the sperm are produced in the testes.
From the testes,they pass through $10-12$ small ducts called vasa efferentia.
These vasa efferentia enter the kidneys on their side and open into the Bidder's canal.
From the Bidder's canal,the sperms are carried by the urinogenital duct,which finally opens into the cloaca.
From the cloaca,the sperms are released outside through the cloacal aperture.
Therefore,the correct pathway is: Testis $\rightarrow$ Vasa efferentia $\rightarrow$ Bidder's canal $\rightarrow$ Urinogenital duct $\rightarrow$ Cloaca $\rightarrow$ Cloacal aperture.

(B) In the anatomy of a frog,the female reproductive system is highly prolific. $A$ single mature female frog is capable of laying approximately $2500$ to $3000$ ova at a time during the breeding season. This high number of eggs ensures the survival of the species despite high predation rates in their aquatic environment.

(D) In frogs,fertilization is external,meaning it occurs in water ($A$ is correct).
Development is indirect,involving a larval stage called the tadpole ($B$ is correct).
The tadpole undergoes metamorphosis,passing through various stages to transform into an adult frog ($C$ is correct).
Therefore,all the given statements are correct.

(D) In a frog,the deoxygenated blood from various parts of the body is collected by the venous system and brought to the heart through two large veins known as the vena cavae (precaval and postcaval). These vessels empty into the sinus venosus,which then leads into the right atrium of the heart.

(D) The renal portal system in a frog is a specialized venous network that carries blood from the posterior (lower) parts of the body directly to the kidneys before it returns to the heart.
This system is essential for the excretion of nitrogenous wastes from the lower limbs and posterior regions of the body.
Therefore,it acts as a link between the lower part of the body and the kidneys.

(B) Frogs exhibit cutaneous respiration (through the skin) in both water and on land.
In water,the skin acts as the primary respiratory organ,and the buccal cavity also contributes to gas exchange.
On land,frogs respire through their skin (cutaneous respiration),buccal cavity (buccal respiration),and lungs (pulmonary respiration).
Therefore,the statement provided is scientifically accurate for both environments.

(A) The heart of a frog is indeed muscular and three-chambered,consisting of two atria and one ventricle.
This structure is an adaptation for its semi-aquatic life.
The conus arteriosus is a specialized structure attached to the ventricle that helps in the distribution of blood.
It receives mixed blood from the ventricle and directs it to different parts of the body,including the lungs and skin,through various arterial arches.
Therefore,the reason correctly explains why the heart structure is significant in the context of blood circulation in frogs.

(C) In the heart of a frog,the ventricle is a thick-walled,muscular chamber.
It pumps blood into a sac-like structure called the conus arteriosus.
The conus arteriosus is located on the ventral side of the heart.
Therefore,the correct option is $C$.

(B) The brain of a frog is divided into three main parts: forebrain,midbrain,and hindbrain.
$1$. The forebrain consists of a pair of olfactory lobes,a pair of cerebral hemispheres,and a diencephalon.
$2$. The midbrain consists of a pair of optic lobes.
$3$. The hindbrain consists of the cerebellum and medulla oblongata.
Therefore,the optic lobes are part of the midbrain,not the forebrain.

(A) Frogs exhibit cutaneous respiration through their moist skin during both aestivation (summer sleep) and hibernation (winter sleep).
In this state,the metabolic rate is reduced,and the skin acts as the primary respiratory surface for the exchange of gases.
While lungs and the buccal cavity are used for respiration on land during active periods,cutaneous respiration is the exclusive or primary method during periods of dormancy like aestivation.

(B) In male frogs,the vasa efferentia are a series of fine tubules that arise from the testes. These tubules enter the kidneys on their respective sides and open into the Bidder's canal. The number of vasa efferentia typically ranges from $10$ to $12$.

(D) Statement-$I$ is correct: In frogs,the eyes and internal ears are highly developed and well-organised sensory structures.
Statement-$II$ is correct: Sensory papillae (for touch),taste buds (for taste),and nasal epithelium (for smell) are indeed cellular aggregations located around nerve endings that function as sensory receptors.
Therefore,both statements are correct.

(C) In the heart of a frog, the $Sinus$ $venosus$ is a thin-walled, triangular chamber.
It is located on the dorsal side of the heart.
Its primary function is to receive blood from the major veins (vena cava) and join the right atrium to deliver deoxygenated blood into the heart.

(D) Frogs and humans share several anatomical features,such as the presence of a thyroid gland,parathyroid glands,paired cerebral hemispheres,and a hepatic portal system.
However,a key difference lies in the nature of their red blood cells $(RBCs)$.
In humans,mature red blood cells are enucleated (lacking a nucleus) to maximize space for hemoglobin.
In contrast,frogs possess nucleated red blood cells throughout their life cycle.
Therefore,the correct option is $D$.

(B) In the reproductive system of a frog,the female reproductive organs consist of a pair of ovaries. The ovaries are situated near the kidneys and do not have a functional connection with them. $A$ mature female frog can lay $2500-3000$ ova at a time during the breeding season.

(A) In frogs,the life cycle includes a larval stage known as the tadpole.
Since the organism does not develop directly into the adult form but passes through a distinct larval stage,this is termed as indirect development.
The process by which the tadpole (larva) transforms into the adult frog is called metamorphosis.
Therefore,the reason correctly explains why the development is considered indirect.

(B) The correct matches are as follows:
$1$. Vocal Sac $(A)$ is a characteristic feature of male frogs, representing sexual dimorphism $(P)$.
$2$. During hibernation and aestivation, the frog respires only through its skin $(R)$.
$3$. The renal portal system $(C)$ is a vascular system that collects blood from the lower parts of the body and transports it to the kidneys $(U)$.
$4$. Bidder's canal $(D)$ is present in the kidneys of male frogs and receives sperms from the vasa efferentia $(X)$.
Therefore, the correct sequence is $A \rightarrow P, B \rightarrow R, C \rightarrow U, D \rightarrow X$.

(A) In frogs,the testes are yellowish,ovoid structures paired and attached to the upper part of the kidneys by a double fold of peritoneum called the mesorchium.
$1$. $Mesorchium$ is the fold of the peritoneum that suspends the testes.
$2$. $Perichondrium$ is the connective tissue covering cartilage.
$3$. $Nuptial$ $pad$ is a secondary sexual character found on the first digit of the forelimbs of male frogs.
$4$. $Copulatory$ $pad$ is another term often used for nuptial pads in some contexts,but it is not the structure that attaches the testes to the kidneys.

(A) The correct statements are $A$ and $C$.
$1$. $Bidder's$ canals are present in the kidneys of male $Frogs$ and are involved in the transport of spermatozoa.
$2$. Copulatory pads (nuptial pads) are present on the first digit of the forelimbs in male $Frogs$ to assist in amplexus during mating.
$3$. Vocal sacs are present in male $Frogs$ to produce sound for attracting females.
$4$. The $Cloaca$ is a common chamber for the urinary,reproductive,and digestive tracts,and it is present in both male and female $Frogs$.

(D) Statement $A$ is correct: The hepatic portal system is a special venous connection between the intestine and the liver.
Statement $B$ is incorrect: Frogs have $10$ pairs of cranial nerves,not $12$.
Statement $C$ is correct: In female frogs,the ureters and oviducts open separately into the cloaca.
Statement $D$ is incorrect: The hind-brain consists of the cerebellum and medulla oblongata; the optic lobes are part of the mid-brain.
Statement $E$ is correct: The sinus venosus is a triangular chamber that joins the right atrium of the heart.
Therefore,statements $A, C,$ and $E$ are correct.