Class-Mammalia Questions in English

(C) The correct answer is $C$.
Homeothermic animals,also known as warm-blooded or endothermic animals,are those that maintain a constant body temperature regardless of the environmental temperature.
This internal heat is generated through metabolic reactions within the body.
Among the given options,the $Rabbit$ is a mammal,and all mammals (along with birds) are homeothermic.
Toads,lizards,and frogs are poikilothermic (cold-blooded) animals whose body temperature fluctuates with the environment.

(A) Viviparity is the condition where an animal gives birth to live young ones instead of laying eggs.
Among the given options,whales are mammals (specifically Eutherian mammals),which are characterized by viviparity.
Bony fishes,turtles,and running birds (like ostriches) are generally oviparous,meaning they lay eggs.

(B) The ability to change skin colour (metachrosis) is primarily found in certain fish,amphibians,and reptiles (like chameleons and garden lizards) to camouflage or communicate.
$Aves$ (birds) and $Mammals$ (like the horse) do not possess the physiological mechanism to change their skin colour.
Therefore,the horse is the correct answer.

(C) Birds $(Aves)$ and bats $(Mammalia)$ are both warm-blooded $(Homoiothermic)$ animals and possess a $4-$chambered heart. Both groups also utilize lungs for respiration,which are connected to a trachea. However,a $Diaphragm$ is a characteristic muscular partition that separates the thoracic cavity from the abdominal cavity and is unique to mammals. Therefore,birds lack a diaphragm,whereas bats,being mammals,possess one.

(D) The renal portal system is a circulatory arrangement in which blood from the posterior part of the body (hind limbs) is collected and passed through the kidneys before returning to the heart.
This system is present in amphibians,reptiles,and birds.
However,in mammals,the renal portal system is completely absent.
Therefore,the correct option is $D$.

(D) The middle ear of mammals contains three distinct ear ossicles known as $Malleus$,$Incus$,and $Stapes$.
These bones are responsible for transmitting sound vibrations from the tympanic membrane to the inner ear.
Amphibians,reptiles,and birds typically possess only a single ear ossicle,known as the columella.

(C) In mammals,the systemic arch is derived from the left fourth aortic arch,meaning only the left aortic arch persists.
In birds,the systemic arch is derived from the right fourth aortic arch.
In reptiles (including the order Crocodilia),both left and right systemic arches are present.
Therefore,only mammals possess exclusively the left aortic arch.

(B) $Prototherians$ are primitive mammals that lay eggs. They are oviparous mammals,often described as reptile-like mammals,and are primarily confined to the Australian region.

(A) The presence of hair on the skin is a unique and defining characteristic of mammals.
Bats belong to the class $Mammalia$ because they possess mammary glands,external ears (pinnae),and their body is covered with hair,which are key diagnostic features of this class.
While bats can fly,this is a result of convergent evolution and is not a defining feature of mammals,as many other mammals cannot fly.

(A) $Manis$ (Pangolin or scaly anteater) belongs to the order $Pholidota$ of the class $Mammalia$.
$Planorbis$ is a genus of freshwater snails belonging to the phylum $Mollusca$.
$Hydrophis$ is a genus of sea snakes belonging to the class $Reptilia$.
$Psittacula$ is a genus of parrots belonging to the class $Aves$.

(B) The presence of external ears,also known as $pinnae$,is a unique and defining characteristic of the class $Mammalia$.
While some mammals (like whales) have modified ear structures,the presence of $pinnae$ is a diagnostic feature used to distinguish mammals from other vertebrate classes such as $Aves$ (birds) and $Reptilia$ (reptiles),which typically have ear openings covered by feathers or scales without external flaps.

(B) $Eutheria$ includes $viviparous$ placental mammals. These mammals give birth to relatively well-developed young ones,as they possess a placenta for the nourishment of the fetus during development inside the mother's uterus.

(B) Marsupials are a group of mammals belonging to the infraclass $Metatheria$.
Like all mammals,they give birth to live young,which classifies them as $Viviparous$.
Although their young are born at a very early stage of development and continue to grow in a pouch $(marsupium)$,the process of giving birth to live young rather than laying eggs confirms their $Viviparous$ nature.

(C) is the correct answer. $Heloderma$ is a genus of venomous lizards,which belongs to the class $Reptilia$. In contrast,Ant eaters,Echidna,and Dolphins are all mammals belonging to the class $Mammalia$.

(A) Animals belonging to the order $Rodentia$ are characterized by having a single pair of continuously growing,rootless,chisel-like incisors in each jaw.
These incisors are used for gnawing and are kept sharp by the constant wear against each other.
Therefore,the correct option is $A$.

(D) The correct answer is $D$. Mucus glands are primarily found in animals that use their skin for cutaneous respiration (e.g.,amphibians). Mucus keeps the skin moist,which is essential for the diffusion of gases. Mammals do not use their skin for respiration; instead,they rely on lungs,and their skin is adapted for protection and thermoregulation,thus lacking mucus glands.

(B) The rabbit belongs to the order $Lagomorpha$ within the class $Mammalia$. Unlike rodents,lagomorphs have four incisors in the upper jaw,whereas rodents only have two.

(C) Whales are aquatic animals that possess mammary glands for nourishing their young ones. They are warm-blooded,breathe through lungs,and have hair on their bodies at some stage of their life cycle. These characteristics classify them under the class $Mammalia$.

(A) $Didelphis$ (opossum) is a tree-dwelling mammal found in America. It belongs to the infraclass Metatheria (marsupials).

(B) $Monotremes$ (Prototheria) are a unique group of mammals that exhibit a combination of reptilian and mammalian characteristics.
Key reptilian features include laying eggs $(oviparous)$ and the presence of a $cloaca$.
Key mammalian features include the presence of mammary glands and hair on the body.

(B) The kangaroo $(Macropus)$ is a mammal found primarily in the Australian region.
It belongs to the infraclass $Metatheria$,which is commonly referred to as $Marsupialia$ (pouched mammals).
These animals are characterized by giving birth to relatively undeveloped young,which then climb into the mother's pouch to complete their development.

(C) $Monotremata$ is an order of mammals that lay eggs instead of giving birth to live young. They are characterized by having a single common opening for the digestive,reproductive,and urinary tracts,known as the cloaca. Examples include the platypus and echidna.

(B) The most characteristic features of mammals are the presence of mammary glands (milk-producing glands) for nourishing their young ones and the presence of hair on the skin. These features are unique to the class $Mammalia$ and are not found in other vertebrate groups.

(B) The presence of mammary glands (milk-producing glands) is the most characteristic feature of the class $Mammalia$.
These glands are used by females to nourish their young ones.
Therefore,all mammals,whether they are prototherians (egg-laying),metatherians (marsupials),or eutherians (placental),possess mammary glands.

(B) Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion.
They belong to the order $Artiodactyla$ (even-toed ungulates) and the suborder $Ruminantia$.
Examples include cattle,sheep,goats,and deer.

(C) The class $Mammalia$ includes the $Blue$ $Whale$ $(Balaenoptera$ $musculus)$, which is the largest animal known to have ever existed on Earth.

(A) The correct answer is $A$.
Prototheria (subclass of Mammalia) includes primitive egg-laying mammals,such as the platypus and echidna and echidna.
Unlike Metatheria (marsupials) and Eutheria (placental mammals),Prototherians do not possess a true placenta for fetal development,as they reproduce by laying eggs.

(B) Metatherians are commonly known as marsupials.
They are characterized by giving birth to relatively undeveloped young, which then climb into a pouch $(marsupium)$ on the mother's body to complete their development.
Among the given options, the $Kangaroo$ is a well-known marsupial (metatherian).
$Echidna$ is a prototherian (monotreme), while $Shrew$ and $Pangolin$ are eutherian (placental) mammals.

(B) Birds and mammals possess a four-chambered heart,consisting of two atria and two ventricles.
This anatomical structure ensures that oxygenated blood (from the lungs) and deoxygenated blood (from the body tissues) are completely separated within the heart,preventing any mixing.
In contrast,amphibians and most reptiles have three-chambered hearts (or incomplete four-chambered in crocodiles),which leads to the mixing of oxygenated and deoxygenated blood.

(D) Bats and whales both belong to the class $Mammalia$ within the phylum $Chordata$.
Bats are flying mammals,while whales are aquatic mammals.
Both possess characteristic mammalian features such as mammary glands,hair on the body,and the ability to give birth to live young.

(A) bat is a flying mammal.
It belongs to the class $Mammalia$ because it possesses mammary glands,has hair on its body,and gives birth to young ones (viviparous) rather than laying eggs.

(B) Mammals are generally viviparous,meaning they give birth to live young.
However,the order $Monotremata$ is a unique group of mammals that are oviparous,meaning they lay eggs.
$Ornithorhynchus$ (commonly known as the Platypus) is a well-known example of a monotreme mammal.
Therefore,the correct option is $B$.

(C) The presence of a double vagina (or bifurcated vagina) is a characteristic feature of female marsupials $(Marsupialia)$.
In these mammals,the reproductive tract is divided into two lateral vaginas,which lead to two separate uteri,while a third central canal is often used for birth.

(B) Viviparous animals are those that give birth to live young ones.
Most mammals are viviparous.
The $Platypus$ (Ornithorhynchus) is a monotreme,which is an egg-laying mammal.
Therefore,it is oviparous,not viviparous.
Mole,Kangaroo,and Shrew are all placental or marsupial mammals that give birth to live young.

(C) The order $Cetacea$ belongs to the class $Mammalia$.
It consists of fully aquatic mammals.
Common examples of animals included in this order are whales,dolphins,and porpoises.
Therefore,the correct option is $C$.

(A) Mammals are classified into three subclasses: $Prototheria$,$Metatheria$,and $Eutheria$.
$Prototheria$ (e.g.,$Ornithorhynchus$ or platypus) are egg-laying mammals that possess a $cloaca$,which is a common opening for the digestive,urinary,and reproductive tracts.
$Metatheria$ (marsupials) and $Eutheria$ (placental mammals) do not possess a $cloaca$; instead,they have separate openings for these systems.

(B) $Perissodactyla$ (Greek, $perissos$ - odd + $dactylos$ - toes) are the odd-toed hoofed mammals or ungulates.
They possess an odd number of toes ($1$ or $3$) on each foot.
Therefore, horses, asses, and zebras are classified under the order $Perissodactyla$.

(A) Prototherians,also known as monotremes,are egg-laying mammals.
$Ornithorhynchus$ (Platypus) and $Tachyglossus$ (Echidna) are the primary examples of prototherians.
$Macropus$ (Kangaroo) is a metatherian (marsupial).
$Opossum$ is also a metatherian.
$Bradypus$ (Sloth) is an eutherian (placental mammal).
Therefore,the correct answer is $A$.

(B) . $Echidna$ or spiny anteater $(Tachyglossus)$ is an egg-laying primitive $Prototherian$ mammal. It is terrestrial and is found in Australia,Tasmania,and New Guinea.

(D) Organisms that maintain a constant body temperature regardless of the external environment are known as homeotherms or warm-blooded animals.
Among the given options,$A$ (Earthworm),$B$ (Snake),and $C$ (Frog) are poikilotherms (cold-blooded animals),meaning their body temperature fluctuates with the environment.
$D$ (Cow) is a mammal,and all mammals are homeotherms,meaning they maintain a constant body temperature.
Therefore,the correct answer is $D$.

(D) The correct answer is $D$.
$Fish$ belongs to the class $Pisces$ (cold-blooded aquatic vertebrates).
$Whale$,$Porpoise$,and $Bat$ are all members of the class $Mammalia$ (warm-blooded vertebrates that possess mammary glands and hair).

(D) Dolphins belong to the class $Mammalia$ because they possess mammary glands,have hair on their bodies (at some stage of development),and are warm-blooded animals.
They breathe air through lungs and give birth to live young ones,which are characteristic features of mammals.

(C) Rabbit eats its own faeces. This behavior is known as coprophagy,and such animals are called coprophagous. This process allows the animal to re-ingest nutrients that were not fully absorbed during the first passage through the digestive tract.

(C) $Ornithorhynchus$,commonly known as the platypus,belongs to the order $Monotremata$.
These are unique mammals that lay eggs instead of giving birth to live young.
Therefore,it is classified as a monotreme mammal.

(C) Mammals are characterized by the presence of hair on their skin. However,in the order $Cetacea$ (which includes whales,dolphins,and porpoises),hair is either completely absent or restricted to a few sensory bristles around the mouth in adults. This is an adaptation to their fully aquatic lifestyle,where hair would increase drag and interfere with swimming efficiency.

(D) The Sea lion $(Zalophus)$ is a large-eared seal.
It belongs to the class Mammalia and the order Carnivora.

(A) The pinna (external ear) is a characteristic feature of most mammals.
However,in the order $Sirenia$ (which includes aquatic mammals like manatees and dugongs),the pinna is absent as an adaptation to their fully aquatic lifestyle.
$Primates$ and $Rodentia$ possess well-developed pinnae.
Therefore,the correct answer is $Sirenia$.

(D) The correct answer is $D$. In the male platypus,a grooved erectile poison spine is present on the tarsus of the hind limb,which is connected to a crural (poison) gland located in the thigh. This poison is primarily used for defense and to immobilize rivals or females during the mating season.

(A) The correct answer is $Ornithorhynchus$ (also known as the Platypus).
Male platypuses have spurs on their hind limbs that are connected to venom glands,which they use for defense or during mating competition.
$Echidna$ is a monotreme but is not venomous.
$Guinea$ $pig$ is a rodent and is not venomous.
$Snake$ is a reptile,not a mammal.