Class-Mammalia Questions in English

(D) Mammals are unique among vertebrates because they possess a muscular diaphragm,which aids in respiration,and mammary (milk-producing) glands,which are used to nourish their young. While other features like a four-chambered heart or heterodont teeth are common,they are not present in every single mammal without exception (e.g.,some monotremes have different characteristics,and not all mammals have $12$ pairs of cranial nerves).

(D) Whales are exclusively viviparous. In viviparous animals (the majority of mammals,including human beings),the zygote develops into a young one inside the body of the female organism.
After attaining a certain stage of growth,the young ones are delivered out of the body of the female organism.

(D) The Assertion is incorrect because many cold-blooded animals (ectotherms) do possess fat layers or fat bodies for energy storage.
The Reason is correct because cold-blooded animals,such as certain reptiles and amphibians,rely on stored fat reserves to sustain metabolic activities during periods of dormancy like hibernation or aestivation.
Therefore,the Assertion is incorrect,but the Reason is correct.

(B) Both the Assertion and the Reason are correct statements.
Bats and whales are classified as mammals because they possess mammary glands,have hair (at some stage of development),and are warm-blooded (homeothermic).
They also possess a $4$-chambered heart,which is a characteristic feature of mammals.
However,the presence of a $4$-chambered heart is not the defining characteristic that classifies an animal as a mammal; rather,it is the presence of mammary glands and other mammalian traits.
Therefore,the Reason is a correct statement but does not explain why they are classified as mammals.

(C) The Assertion is correct because the duck-billed platypus and the spiny ant-eater (echidna) are prototherian mammals that lay eggs (oviparous) but possess mammary glands.
The Reason is incorrect because,while mammals generally have $7$ cervical vertebrae,the number of cranial nerves in mammals is $12$ pairs,but this specific anatomical feature is not the defining characteristic that classifies them as mammals. Furthermore,the statement implies these are the reasons for their classification as mammals,which is scientifically inaccurate; they are classified as mammals due to the presence of mammary glands,hair,and a diaphragm.

(N/A) $1$. Homeothermy (Endothermy): It is the ability of an organism to maintain a constant internal body temperature regardless of the external environmental temperature. Examples include mammals and birds.
$2$. Poikilothermy (Ectothermy): It is the condition where an organism's internal body temperature fluctuates in accordance with the changes in the external environmental temperature. Examples include most reptiles,amphibians,and fish.

(N/A) $\rightarrow$ Mammals are found in a variety of habitats - polar ice caps,deserts,mountains,forests,grasslands,and dark caves.
$\rightarrow$ Some of them have adapted to fly or live in water.
$\rightarrow$ The most unique mammalian characteristic is the presence of milk-producing glands (mammary glands) by which the young ones are nourished.
$\rightarrow$ They have two pairs of limbs,adapted for walking,running,climbing,burrowing,swimming,or flying.
$\rightarrow$ The skin of mammals is unique in possessing hair.
$\rightarrow$ External ears or pinnae are present.
$\rightarrow$ Different types of teeth are present in the jaw.
$\rightarrow$ The heart is four-chambered.
$\rightarrow$ They are homoiothermous (warm-blooded).
$\rightarrow$ Respiration is by lungs.
$\rightarrow$ Sexes are separate and fertilisation is internal.
$\rightarrow$ They are generally viviparous,with few exceptions,and development is direct.
$\rightarrow$ Examples: Oviparous - Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo),Pteropus (Flying fox),Camelus (Camel),Macaca (Monkey),Rattus (Rat),Canis (Dog),Felis (Cat),Elephas (Elephant),Equus (Horse),Delphinus (Common dolphin),Balaenoptera (Blue whale),Panthera tigris (Tiger),Panthera leo (Lion).

(N/A) The most evolved class in the animal kingdom is Class Mammalia. Its characteristics are as follows:
$1$. Habitat: They are found in a variety of habitats like polar ice caps,deserts,mountains,forests,grasslands,and dark caves.
$2$. Adaptations: Some have adapted to fly (e.g.,Bat) or live in water (e.g.,Blue Whale).
$3$. Mammary Glands: The presence of milk-producing glands (mammary glands) is a unique characteristic,by which the young ones are nourished.
$4$. Limbs: They have two pairs of limbs,adapted for walking,running,climbing,burrowing,swimming,or flying.
$5$. Skin: The skin of mammals is unique in possessing hair.
$6$. External Ears: Pinnae (external ears) are present.
$7$. Dentition: Different types of teeth (incisors,canines,premolars,and molars) are present in the jaw.
$8$. Heart: The heart is four-chambered. The aortic arch curves to the left.
$9$. Physiology: They are homoiothermous (warm-blooded) animals. Sexes are separate and fertilization is internal.
$10$. Reproduction: They are generally viviparous (giving birth to young ones) with direct development,with few exceptions like the oviparous Platypus (Ornithorhynchus).
$11$. Examples: Platypus (Ornithorhynchus),Kangaroo (Macropus),Bat (Pteropus),Blue Whale (Balaenoptera).

(B) Viviparous animals are those that give birth to young ones directly.
Most mammals, including humans, are viviparous.
Examples of viviparous animals include:
- Kangaroo $(Macropus)$
- Bat $(Pteropus)$
- Camel $(Camelus)$
- Monkey $(Macaca)$
- Rat $(Rattus)$
- Dog $(Canis)$
- Cat $(Felis)$
- Elephant $(Elephas)$
- Horse $(Equus)$
- Dolphin $(Delphinus)$
- Blue Whale $(Balaenoptera)$
- Tiger $(Panthera \text{ } tigris)$
- Lion $(Panthera \text{ } leo)$
Among the given options, Kangaroo and Blue Whale are classic examples of viviparous mammals.

(N/A) $\rightarrow$ Mammalia are found in a variety of habitats - polar ice caps,deserts,mountains,forests,grasslands and dark caves.
$\rightarrow$ Some of them have adapted to fly or live in water.
$\rightarrow$ The most unique mammalian characteristic is the presence of milk-producing glands (mammary glands) by which the young ones are nourished.
$\rightarrow$ They have two pairs of limbs,adapted for walking,running,climbing,burrowing,swimming or flying.
$\rightarrow$ The skin of mammals is unique in possessing hair.
$\rightarrow$ External ears or pinnae are present.
$\rightarrow$ Different types of teeth are present in the jaw.
$\rightarrow$ Heart is four-chambered.
$\rightarrow$ They are homoiothermous (warm-blooded).
$\rightarrow$ Respiration is by lungs.
$\rightarrow$ Sexes are separate and fertilisation is internal.
$\rightarrow$ They are viviparous with few exceptions and development is direct.
$\rightarrow$ Examples: Oviparous - Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo),Pteropus (Flying fox),Camelus (Camel),Macaca (Monkey),Rattus (Rat),Canis (Dog),Felis (Cat),Elephas (Elephant),Equus (Horse),Delphinus (Common dolphin),Balaenoptera (Blue whale),Panthera tigris (Tiger),Panthera leo (Lion).

(B) $(i)$ Animals that maintain a constant body temperature regardless of the external environment are known as $warm-blooded$ (homeothermic) animals.
$(ii)$ Mammals are characterized by giving birth to young ones, which makes them $viviparous$ animals.
Therefore, the correct choice is $(i)$ $warm-blooded$, $(ii)$ $viviparous$.

(D) Primates are a group of mammals that include monkeys,apes,and humans.
- Rats belong to the order $Rodentia$.
- Tigers belong to the order $Carnivora$.
- Cows belong to the order $Artiodactyla$.
Since none of these organisms belong to the order $Primates$,the correct answer is $D$.

(D) Primates are a group of mammals that include lemurs,monkeys,apes,and humans.
Among the given options,$A$ (Sheep),$B$ (Deer),and $C$ (Horse) are ungulates (hoofed mammals).
$D$ (Ape) belongs to the order $Primates$.
Therefore,the correct option is $D$.

(C) The correct answer is $C$.
$A$,$B$,and $D$ (Whale,Bat,and Cheetah) are all mammals.
$C$ (Brachiosaurus) is a dinosaur,which belongs to the class Reptilia.
Therefore,Brachiosaurus is the odd one out as it does not belong to the class Mammalia.

(B) pouched mammal is known as a $Marsupial$.
These mammals give birth to relatively undeveloped young,which then climb into a pouch on the mother's abdomen to continue their development.
Examples include kangaroos and koalas.
Therefore,the correct option is $B$.

(C) The $Koala$ ($Phascolarctos$ $cinereus$) is an arboreal herbivorous marsupial native to Australia. Unlike dolphins,whales,and seals,which are aquatic or semi-aquatic mammals adapted to life in water,the koala is strictly terrestrial and lives in eucalyptus trees. Therefore,it is not an aquatic animal.

(A) Mammals are successful because they are homeothermic (endothermic) organisms.
They maintain a constant body temperature regardless of the external environmental conditions.
This ability allows them to remain active and survive in diverse climatic conditions,ranging from extreme cold to extreme heat.
Therefore,the ability to maintain a constant body temperature is the key factor for their success.

(A) In animals,reserve food is typically stored in the form of glycogen and fat.
$A$. Man and Monkey are both animals (mammals).
$B$. $Cuscuta$ is a parasitic plant (stores starch).
$C$. $Bladderwort$ and $Cuscuta$ are plants (store starch).
$D$. $Bladderwort$ and $Venus$ $fly$ $trap$ are insectivorous plants (store starch).
Therefore,both Man and Monkey store reserve food as glycogen and fat.

(D) Echolocation is a biological sonar used by several animal species. Bats produce high-frequency ultrasonic sounds that bounce off objects in their environment. By listening to the echoes of these sounds,they can determine the location,size,and distance of objects,which helps them navigate and hunt in the dark.

(C) Metatherians are commonly known as pouched mammals.
They possess a specialized abdominal pouch called a marsupium.
The embryo is born in an underdeveloped state and completes its development within this marsupium.

(A) Echidna belongs to the group $Prototheria$ of the class $Mammalia$.
It is oviparous,meaning it lays eggs instead of giving birth to live young.
Only the female incubates the eggs,and the young ones lap the milk secreted by the mammary glands.

(B) $Oryctolagus$ $cuniculus$ (rabbit) is a representative of class $Mammalia$.
$1.$ Dentition in all mammals is heterodont (i.e.,presence of dissimilar types of teeth). Thus,statement $I$ is true.
$2.$ Canines are completely absent in rabbits,not just poorly developed. Thus,statement $II$ is false.
$3.$ Incisors in rabbits are well-developed,sharp,and chisel-like,used for gnawing. Thus,statement $III$ is false.
$4.$ Rabbits are herbivorous,and due to the absence of canines,a gap exists between the incisors and premolars,known as a diastema. Thus,statement $IV$ is true.
$5.$ The dental formula of a rabbit is $I \frac{2}{1}, C \frac{0}{0}, P m \frac{3}{2}, M \frac{3}{3}$,which gives a total of $28$ teeth. Thus,statement $V$ is true.
Therefore,statements $I, IV,$ and $V$ are correct.

(C) The tusks of an elephant are its second upper incisors.
These teeth grow continuously throughout the life of the elephant.

(B) Thecodont dentition refers to teeth that are embedded in deep sockets of the jaw bone.
$1.$ Crocodiles and mammals possess thecodont teeth.
$2.$ Sphenodon (a reptile) possesses acrodont teeth, where teeth are attached to the crest of the jaw bone.
$3.$ Scoliodon (a cartilaginous fish) also possesses acrodont teeth.
Therefore, only crocodiles and mammals exhibit thecodont teeth.

(A) The Haversian canal is a microscopic structure found within the compact bone of mammals. It consists of a central canal containing blood vessels and nerves,surrounded by concentric layers of bone matrix called lamellae. This system,known as the Haversian system or osteon,is a characteristic feature of mammalian bone tissue.

(B) The presence of seven cervical vertebrae in the neck is a common feature in all mammals. These vertebrae are acoelous and are typically covered by cartilaginous pads,i.e.,epiphysis. This characteristic remains constant regardless of the length of the neck in different mammalian species.

(A) The organisms listed are aquatic,but they belong to different biological classes.
$1$. Dolphins are aquatic mammals belonging to the order $Cetacea$.
$2$. Seals are semi-aquatic marine mammals belonging to the order $Carnivora$.
$3$. Sea cows (manatees and dugongs) are fully aquatic herbivorous mammals belonging to the order $Sirenia$.
$4$. Penguins are flightless birds belonging to the class $Aves$.
Therefore,penguins are the only organisms in the list that are not mammals.

(C) Most mammals are viviparous,meaning they give birth to live young. However,there are exceptions known as monotremes. The Duck-billed platypus $(Ornithorhynchus)$ is a well-known example of an oviparous mammal,which means it lays eggs instead of giving birth to offspring.

(A) Mammals are characterized by the presence of a diaphragm,which is a muscular partition separating the thorax from the abdomen,a four-chambered heart,and lungs for respiration.
Viviparity is a common trait but not absolute,as some mammals like the $Platypus$ are oviparous (egg-laying).
Feathers are characteristic of birds,while gills and fins are typical of aquatic organisms like fish.
Neural glands are not a feature of mammals.
Therefore,the correct set of mammalian characters is diaphragm,four-chambered heart,and lungs.

(A) In mammals,the cloaca is typically absent,as they possess separate openings for the digestive and urogenital tracts.
External ears (pinnae) are a characteristic feature of most mammals.
Mammalian mature red blood cells $(RBCs)$ are non-nucleated to increase surface area for oxygen transport.
Mammals are ureotelic,meaning they excrete urea as their primary nitrogenous waste product.
Therefore,the statement that a cloaca is present is incorrect.

(B) Mammals are classified into three subclasses: Prototheria (Monotremata),Metatheria (Marsupialia),and Eutheria (Placentalia).
Monotremes are egg-laying mammals.
According to the classification provided:
$1$. $Ornithorhynchus$ (Platypus) belongs to the subclass Prototheria (Monotremata).
$2$. $Macropus$ (Kangaroo) belongs to the subclass Metatheria (Marsupialia).
$3$. $Balaenoptera$ (Blue whale) and $Elephas$ (Elephant) belong to the subclass Eutheria (Placentalia).
Therefore,the correct option is $B$.

(C) The Assertion is correct because in metatherians (marsupials),the scrotum is located anterior to the penis.
The Reason is incorrect because in prototherians (monotremes),the testes are abdominal and do not descend into a scrotum at all.
Therefore,the correct option is $C$.

(A) Assertion is correct because the duck-billed platypus and the spiny ant-eater are oviparous (egg-laying) mammals.
They are classified as mammals because they possess characteristic mammalian features,such as the presence of seven cervical vertebrae in the neck and mammary glands (though they lack teats).
Since the Reason provides the specific anatomical evidence that justifies their classification as mammals despite being egg-layers,the Reason is the correct explanation for the Assertion.

(B) Assertion is correct because bats (order $Chiroptera$) and whales (order $Cetacea$) possess mammary glands and are classified as mammals.
Reason is correct because both bats and whales exhibit echolocation (used for navigation and hunting) and possess a four-chambered heart,which is a characteristic feature of mammals.
However,the presence of echolocation and a four-chambered heart is not the defining reason why they are classified as mammals; they are classified as mammals due to the presence of mammary glands,hair,and other mammalian traits. Thus,Reason is not the correct explanation for Assertion.

(A) Most mammals are viviparous,meaning they give birth to live young. However,members of the order Monotremata are an exception as they are oviparous (egg-laying mammals).
$1$. $Ornithorhynchus$ (Platypus) is a well-known example of a monotreme,which lays eggs.
$2$. $Macropus$ (Kangaroo) is a marsupial,which is viviparous.
$3$. $Pteropus$ (Flying fox) is a placental mammal,which is viviparous.
$4$. $Balaenoptera$ (Blue whale) is a placental mammal,which is viviparous.
Therefore,the correct answer is $Ornithorhynchus$ (Platypus).

(A) To identify the fully aquatic mammals from the given list:
$1$. Whale: Fully aquatic mammal.
$2$. Dog: Terrestrial mammal.
$3$. Dolphin: Fully aquatic mammal.
$4$. Seal: Semi-aquatic mammal (spends time on land and water).
$5$. Shark: Fish (not a mammal).
$6$. Sea cow (Manatee): Fully aquatic mammal.
$7$. Elephant: Terrestrial mammal.
Therefore,the fully aquatic mammals are Whale,Dolphin,and Sea cow. The total count is $3$.

(A) The primary reason for the success of mammals is their ability to maintain a constant internal body temperature,a process known as $thermoregulation$ or $homeostasis$. This allows mammals to survive in diverse and extreme environmental conditions,ranging from freezing polar regions to scorching deserts,by keeping their metabolic processes stable regardless of external environmental fluctuations.

(C) The correct answer is $C$ because the presence of hairs,pinna,and mammary glands are unique features of mammals.
$A$ is incorrect because mammals have a dicondylic skull,whereas a monocondylic skull is found in reptiles and aves.
$B$ is incorrect because the tympanic membrane is also present in amphibians,so it is not a unique feature of mammals.
$D$ is incorrect because mammals exhibit direct development,not indirect development.

(B) Mammals are generally viviparous,meaning they give birth to young ones.
However,there is a small group of mammals known as monotremes that are oviparous,meaning they lay eggs.
$Ornithorhynchus$ (commonly known as the $Platypus$) is a classic example of an oviparous mammal.
$Macropus$ (kangaroo) is a marsupial and is viviparous.
$Aptenodytes$ (penguin) and $Neophron$ (vulture) are birds,not mammals.

(A) The presence of an external ear or pinna is a characteristic feature of the class $Mammalia$.
Among the given options:
$A$. $Elephas$ (Elephant) belongs to the class $Mammalia$ and possesses external ear pinnae.
$B$. $Columba$ (Pigeon) belongs to the class $Aves$,which lacks external pinnae.
$C$. $Hemidactylus$ (Wall lizard) belongs to the class $Reptilia$,which lacks external pinnae.
$D$. $Naja$ (Cobra) belongs to the class $Reptilia$,which lacks external pinnae.
Therefore,the correct option is $A$.

(A) Mammary glands are a characteristic feature of the class $Mammalia$.
$Camelus$ (camel) belongs to the class $Mammalia$.
$Neophron$ (vulture),$Pavo$ (peacock),and $Corvus$ (crow) belong to the class $Aves$ (birds).
Therefore,mammary glands are present in $Camelus$.

(B) The analogy is based on the habitat of mammals.
Fossorial mammals are those that live primarily underground or in burrows (e.g.,kangaroo rats).
Arboreal mammals are those that live primarily in trees (e.g.,lemurs).
Therefore,the correct analogy is: Fossorial mammals: kangaroo rats :: Arboreal mammals: lemurs.
Thus,option $B$ is the correct answer.

(D) The correct answer is $D$ (Mongoose).
$1$. Mammals are classified into three groups: Prototherians (egg-laying mammals like Platypus),Metatherians (marsupials like Kangaroo),and Eutherians (placental mammals).
$2$. $A$ true placenta is a characteristic feature of Eutherians,which allows for the exchange of nutrients and waste between the mother and the fetus.
$3$. Mongoose is a Eutherian mammal and thus possesses a true placenta.
$4$. Kangaroo is a marsupial (Metatherian) with a short-lived yolk-sac placenta,and Platypus is a monotreme (Prototherian) that lays eggs.

(C) The correct answer is $C$.
Animals that give birth to young ones directly are known as viviparous animals.
$1$. Dolphin,kangaroo,bat,and cat are all mammals that exhibit viviparity.
$2$. Kiwi,ostrich,and penguin are birds,which are oviparous (egg-laying).
$3$. Platypus is a monotreme,which is an egg-laying mammal.
Therefore,the group containing only viviparous animals is Dolphin,kangaroo,bat,and cat.