Class-Mammalia Questions in English

(B) The $Cheetah$ $(Acinonyx \text{ } jubatus)$ is widely recognized as the fastest land animal and the fastest running mammal. It can reach speeds of up to $110-120 \text{ } km/h$ in short bursts covering distances up to $500 \text{ } m$.

(A) The presence of a diaphragm is a unique characteristic of mammals.
It is a muscular partition that separates the thoracic cavity from the abdominal cavity and plays a crucial role in respiration.
While four-chambered hearts are also found in birds,and rib cages are present in many vertebrates,the diaphragm is exclusive to the class Mammalia.

(D) Bats belong to the class $Mammalia$ because they possess mammary glands,have hair on their bodies,and give birth to young ones.
Similarly,whales are aquatic mammals that also belong to the class $Mammalia$.
Butterflies are insects (class $Insecta$),flying lizards are reptiles (class $Reptilia$),and birds belong to the class $Aves$.

(A) Kangaroos are marsupials. Marsupials give birth to relatively undeveloped (premature) young ones,which then crawl into the mother's pouch (marsupium) to complete their development. This is a characteristic feature of the order $Marsupialia$.

(C) The correct answer is $C$ (Platypus).
$1$. Mammals are generally characterized by the presence of mammary glands and the birth of live young.
$2$. However,the order $Monotremata$ is a unique group of mammals that lay eggs instead of giving birth to live young.
$3$. The $Platypus$ ($Ornithorhynchus$ $anatinus$) is a well-known example of a monotreme.
$4$. Despite laying eggs,the female $Platypus$ possesses mammary glands and secretes milk to nourish its young,which is a defining characteristic of the class $Mammalia$.

(A) bat is classified under the class $Mammalia$ because it exhibits key mammalian features such as the presence of mammary glands,hair on the skin,and giving birth to young ones (viviparity). Unlike birds,bats do not have feathers,a beak,or lay eggs. Therefore,despite its ability to fly,it is not a bird.

(B) Bats,whales,and rats all belong to the class $Mammalia$.
One of the defining characteristics of mammals is the presence of a muscular diaphragm that separates the thoracic cavity from the abdominal cavity.
While external pinnae are present in bats and rats,they are absent or highly modified in whales.
Testes are located outside the abdominal cavity in many mammals,but this is not a universal feature across all species in the same way the diaphragm is.
Therefore,the presence of a muscular diaphragm is a common feature shared by these mammals.

(D) The class $Mammalia$ is characterized by several unique features that distinguish them from other vertebrates.
$1$. The presence of $hair$ on the skin is a unique feature of mammals.
$2$. The presence of $mammary$ $glands$ (milk-producing glands) is the most distinct characteristic,which is used for the nourishment of their young ones.
$3$. While other animals may have teeth or pinna,these two features ($hair$ and $mammary$ $glands$) are exclusive to the class $Mammalia$.

(B) Mammals are divided into three subclasses: Prototheria,Metatheria,and Eutheria.
$1$. Prototheria are egg-laying mammals (e.g.,Platypus).
$2$. Metatheria are pouched mammals. They give birth to relatively undeveloped young,which then crawl into a marsupium (brood pouch) to complete their development.
$3$. Eutheria are placental mammals that give birth to fully developed young.
Therefore,the correct answer is Metatheria.

(B) The presence of external ears or pinnae is a characteristic feature of the class $Mammalia$. While other vertebrates like reptiles,amphibians,and fishes have internal ear structures for hearing,they lack the external pinnae structure used to collect sound waves.

(B) Mammals are generally viviparous, meaning they give birth to live young. However, there is a small group of mammals known as monotremes that lay eggs. The $Duck-billed$ $Platypus$ $(Ornithorhynchus$ $anatinus)$ is a well-known example of an oviparous (egg-laying) mammal. Kangaroo is a marsupial (viviparous), while whales and rabbits are placental mammals (viviparous).

(A) Mammals are characterized by the presence of mammary glands,hair on the skin,and a diaphragm that separates the thoracic cavity from the abdominal cavity.
$A$. Platypus (Ornithorhynchus) is a monotreme,which is an egg-laying mammal (oviparous). This is a correct statement.
$B$. Bats are mammals and possess hair,not feathers. Feathers are a characteristic feature of birds (Aves).
$C$. Elephants are placental mammals and are viviparous,not ovoviviparous.
$D$. The diaphragm is a unique characteristic feature of mammals,so it is present,not absent.

(C) The presence of $7$ cervical vertebrae is a characteristic feature of almost all mammals,including humans,giraffes,and whales. While the length of the neck varies significantly among these species,the number of cervical vertebrae remains constant at $7$.

(B) Bats use a biological sonar system known as echolocation to navigate and find prey in the dark. They emit high-frequency sound waves (ultrasonic waves) that bounce off objects,allowing them to detect the location,size,and distance of obstacles or prey. This mechanism functions similarly to a radar system.

(C) Mammals are endothermic (warm-blooded) animals. The primary biological advantage of being warm-blooded is the ability to maintain a constant internal body temperature (homeostasis) regardless of the fluctuations in the external environmental temperature. This allows mammals to remain active and inhabit diverse climates,from polar regions to deserts,by regulating their internal heat production and dissipation.

(D) Viviparous animals are those that give birth to young ones directly instead of laying eggs.
Most mammals,including whales (aquatic mammals) and bats (flying mammals),are viviparous.
Ratite birds (like ostriches) are oviparous,meaning they lay eggs.
Therefore,both whales and bats are viviparous organisms.

(B) The $Diaphragm$ is a unique muscular partition that separates the thoracic cavity from the abdominal cavity. It is a characteristic feature found exclusively in mammals and plays a crucial role in respiration by facilitating the expansion and contraction of the lungs.

(B) Warm-blooded animals,also known as endotherms or homeotherms,are organisms that can maintain a constant internal body temperature regardless of the temperature of their surroundings. This process is known as thermoregulation. Examples include birds and mammals. Therefore,the correct characteristic is that their body temperature remains constant.

(B) In mammals,the systemic arch is derived from the left fourth aortic arch of the embryo. During embryonic development,the right fourth aortic arch regresses and becomes vestigial,while the left fourth aortic arch persists to form the systemic arch (aortic arch). Therefore,mammals possess only the left aortic arch.

(C) Mammals are classified into three groups based on their reproductive methods:
$1$. $Monotremata$: Egg-laying mammals (e.g.,Platypus).
$2$. $Metatheria$ (Marsupials): These mammals give birth to relatively undeveloped young,which then crawl into a pouch called a $marsupium$ to complete their development.
$3$. $Eutheria$ (Placental mammals): These mammals have a complex placenta and give birth to fully developed young.
Therefore,the correct answer is $Metatheria$.

(C) Turbinal bones (also known as nasal conchae) are thin,scroll-like bones located in the nasal cavity.
These structures are characteristic features of mammals and birds,as they help in warming,humidifying,and filtering the inhaled air before it reaches the lungs.
Among the given options,mammals possess well-developed turbinal bones in their nasal passages.

(A) In most mammals,mature $RBCs$ (Red Blood Cells) are circular,biconcave,and enucleated (lack a nucleus) to maximize surface area for oxygen transport.
However,members of the family $Camelidae$,such as the camel $(Camelus)$,are an exception.
They possess oval-shaped,biconvex,and nucleated $RBCs$ even in their mature state.

(D) The absence of a thumb is a characteristic feature of $Monkeys$ (specifically,many New World monkeys). In many species of monkeys,the thumb is either absent or vestigial,which helps them in their arboreal (tree-dwelling) lifestyle by allowing them to grasp branches more effectively with their fingers.

(D) Prototheria (e.g.,Platypus,Echidna) are egg-laying mammals. In these organisms,mammary glands are present in both males and females. However,they lack teats or nipples; the milk is secreted onto the skin surface,from where the young ones lick it up.

(C) The Hoolock Gibbon $(Hoolock \text{ hoolock})$ is the only ape species found in India. They are primarily found in the northeastern states of India, such as Assam and Arunachal Pradesh. Other apes like Orangutans, Gorillas, and Chimpanzees are not native to India.

(A) The dental formula represents the number of teeth in one half of the upper and lower jaws.
For a rabbit,the dental formula is $I: 2/1, C: 0/0, PM: 3/2, M: 3/3$.
This means in each half of the jaw,there are $2$ incisors in the upper jaw and $1$ in the lower jaw,$0$ canines,$3$ premolars in the upper jaw and $2$ in the lower jaw,and $3$ molars in both jaws.
Thus,the correct representation is $2/1, 0/0, 3/2, 3/3$.

(A) In mammals,including rabbits,the lower jaw (mandible) is composed of a single pair of bones known as the $Dentary$ bones. These bones fuse at the midline to form the complete lower jaw structure. The $Maxilla$ and $Premaxilla$ are bones of the upper jaw,while the $Palatine$ bone forms part of the hard palate.

(A) The presence of an external ear or pinna is a unique diagnostic characteristic of the class $Mammalia$.
Other characteristic features of mammals include the presence of mammary glands,hair on the skin,and the presence of a diaphragm.

(B) Mammals,birds,and reptiles possess $12$ pairs of cranial nerves,whereas lower vertebrates like fishes and amphibians possess only $10$ pairs.
The $11^{th}$ pair is the Spinal accessory nerve and the $12^{th}$ pair is the Hypoglossal nerve.
These two nerves are absent in lower vertebrates and are considered additional in mammals.

(D) Binocular vision is a type of vision in which both eyes are used together to perceive a single,three-dimensional image of the surroundings. This type of vision allows for better depth perception. In primates,including humans,monkeys,and apes,the eyes are positioned on the front of the face,which facilitates binocular vision. Therefore,all the given options exhibit binocular vision.

(D) Rabbits have eyes located on the sides of their heads,which provides them with a wide field of view,known as monocular vision.
They also possess a cornea,which is the transparent front part of the eye that covers the iris,pupil,and anterior chamber.
While they primarily use monocular vision for detecting predators,they do have the anatomical structures (like the cornea) common to mammalian eyes.
However,in the context of biological classification and anatomical features,the most distinct characteristic listed that describes their visual field is monocular vision,but since they also possess a cornea,the most comprehensive answer is 'All of the above'.

(D) The external ear of a mammal is characterized by the following points:
$1$. The visible outer part of the ear is known as the pinna.
$2$. Monotremes,such as the platypus,lack an external pinna.
$3$. Many mammals,such as horses and cows,possess specialized muscles that allow them to rotate their ears in various directions to capture sound more effectively.
Therefore,all the given statements are correct,making $D$ the correct option.

(D) The class $Mammalia$ is characterized by several unique features.
$1$. Most mammals have $7$ cervical vertebrae (with few exceptions like sloths and manatees).
$2$. They possess thecodont dentition,where teeth are embedded in sockets of the jaw bone.
$3$. They have alveolar lungs for respiration.
$4$. Mammals possess $12$ pairs of cranial nerves,not $10$. $10$ pairs of cranial nerves are a characteristic feature of fishes and amphibians. Therefore,the statement 'Ten pairs of cranial nerves' is incorrect for mammals.

(A) Warm-blooded animals are those that can maintain a constant body temperature regardless of the environmental temperature. This ability is known as endothermy or homeothermy. Therefore,warm-blooded animals are called $Homeothermic$ organisms. In contrast,cold-blooded animals are called $Poikilothermic$ or $Ectothermic$.

(D) Invertebrates are animals that lack a vertebral column (backbone).
$A$. Arthropoda,$B$. Echinodermata,and $C$. Mollusca are all invertebrate phyla.
$D$. Mammalia is a class within the phylum Chordata,which consists of vertebrates (animals with a backbone).
Therefore,Mammalia is not an invertebrate.

(D) bat belongs to the class $Mammalia$.
Although bats have wings and can fly,they possess characteristics that define mammals,such as the presence of mammary glands,hair on their bodies,and the ability to give birth to live young rather than laying eggs.

(C) Mammals $(Class \ Mammalia)$ are highly adaptable animals that are found in a wide variety of habitats,including polar ice caps,deserts,mountains,forests,grasslands,and even aquatic environments like oceans and rivers. Their ability to regulate their body temperature $(endothermy)$ and their diverse physiological adaptations allow them to thrive in almost every corner of the Earth.

(A) The presence of mammary glands is the most unique and defining characteristic of the class $Mammalia$.
These glands are used by females to produce milk for the nourishment of their young ones.
Therefore,the group of animals that possesses mammary glands is known as $Mammals$.

(C) Exoskeleton refers to the external structural covering that provides protection to an organism. In mammals,structures like hair,horns,nails,claws,and hooves are derivatives of the epidermis and serve as an exoskeleton. Feathers are characteristic features of the class $Aves$ (birds) and are not found in mammals.

(D) The presence of a $pinna$ (external ear) is a unique and diagnostic characteristic of the class $Mammalia$.
Other classes like $Reptilia$, $Aves$ (birds), and $Amphibia$ do not possess an external ear flap or $pinna$ to collect sound waves.
Therefore, the correct option is $D$.

(B) In mammals,the systemic aorta (aortic arch) curves to the left side of the heart.
In birds (Aves),the aortic arch curves to the right side.
In amphibians and reptiles,the condition is different as they possess two systemic arches (both left and right) or different arrangements of the aortic arches.

(C) Viviparous animals are those that give birth to young ones directly, rather than laying eggs.
Among the given options, $Mammals$ (Class $Mammalia$) are characterized by being viviparous, with the exception of a few monotremes like the platypus and echidna.
Most amphibians, fishes, and scorpions are oviparous (egg-laying), although some exceptions exist in these groups.
Therefore, the most appropriate general classification for viviparous animals among the choices is $Mammals$.

(C) Mammals are generally viviparous,meaning they give birth to live young. However,there is a small group of mammals known as monotremes that lay eggs. The $Platypus$ ($Ornithorhynchus$ $anatinus$) and the $Echidna$ are the primary examples of oviparous (egg-laying) mammals. Therefore,the correct option is $C$.

(D) The $Chiroptera$ order of mammals consists of bats. Bats are the only mammals capable of true flight. Their forelimbs are modified into wings,which allow them to adapt to an aerial mode of life. Therefore,the correct option is $D$.

(A) Mammals are a diverse group of animals. Among the given options, the $Whale$ is a marine mammal that is fully adapted to an aquatic lifestyle. Its body is streamlined for swimming, and its limbs are modified into flippers. While the $Platypus$ is semi-aquatic, the $Whale$ is the primary example of a mammal completely adapted to life in water.

(C) The duck-billed platypus $(Ornithorhynchus)$ is a member of the class $Mammalia$.
However,unlike most mammals which are viviparous (giving birth to live young),the platypus is oviparous (egg-laying).
Therefore,the statement $S$ is true,but the reason $R$ is false because not all mammals are viviparous.

(A) $1$. The kangaroo is a marsupial mammal belonging to the class $Mammalia$.
$2$. $A$ defining characteristic of mammals is the presence of a diaphragm,which is a muscular partition that separates the thoracic cavity from the abdominal cavity.
$3$. Both statements are scientifically correct,and the presence of a diaphragm is a key diagnostic feature of mammals,thus $R$ correctly explains $S$.

(D) Mammals are characterized by the presence of mammary glands,which produce milk for their young.
They typically possess two pairs of limbs (tetrapod body plan).
Their skin is covered with an exoskeleton of hair.
However,mammals are characterized by 'heterodont' dentition (different types of teeth like incisors,canines,premolars,and molars),not 'homodont' dentition (where all teeth are similar). Therefore,'homodont' is inconsistent with mammals.

(D) $cloaca$ is a common chamber for the digestive,urinary,and reproductive tracts in many vertebrates.
It is present in birds $(Hen)$,amphibians $(Frog)$,and some fishes like cartilaginous fishes $(Dogfish)$.
Mammals,except for monotremes,do not possess a $cloaca$. Instead,they have separate openings for the digestive tract $(anus)$ and the urogenital tract.
Since the $Rabbit$ is a placental mammal,it does not have a $cloaca$.

(C) Whales,bats,and rats all belong to the class $Mammalia$.
One of the defining characteristics of mammals is the presence of a muscular diaphragm that separates the thoracic cavity from the abdominal cavity.
While external ears (pinnae) are present in bats and rats,they are modified in whales.
Testes are located outside the abdomen in many mammals,but this is not a universal feature across all species (e.g.,in some aquatic mammals).
Therefore,the presence of a muscular diaphragm is a diagnostic feature common to all these mammals.