Egg laying mammals are known as monotremes. They are named so because of the presence of a single cloacal opening in their bodies that serves as a passage for eggs or sperms, feces, and urine. As suggested by egg-laying mammal facts, only five species of monotremes are extant, one of which is duck-billed platypus and remaining four belong to the echidna family. 

Humans belong to the order Primates. This group includes lemurs, monkeys, apes, humans and all other related groups of animals. They happen to be the most advanced group of animals. They as found all across the globe as they have evolved to a number of habits and habitats and are still undergoing evolutionary changes in order to survive better.

Humans belong to the order Primates. This group includes lemurs, monkeys, apes, humans and all other related groups of animals. They happen to be the most advanced group of animals. They are found all across the globe as they have evolved to a number of habits and habitats and are still undergoing evolutionary changes in order to survive better.

• Prototherians are primitive egg-laying mammals.
• They have mammary glands but do not have nipples.
• In males, the testes are situated inside the abdominal cavity.
  
• They do not have pinnae.

(A) Artiodactyla order consists of cloven-hooved mammals. Example-Cows, goats.

• Prosimians include The lemurs, lorises and tarsiers and Simians include The monkeys, apes and man.
  
• Prosimians are primitive primates. They retain claws on some digits, having nails on others. The hindlimbs are longer than forelimbs. The tail may be present or lacking.
  
• Simians have nails on the digits. Forelimbs are longer than the hindlimbs. The tail may or may not occur.
  

The birds can lift their body and fly in the air due to the capability that the wings have the structure to push the air in the backward direction. This allows the bird to fly upward and forward by applying force and moving the air back.

Platypus and Echidna are warm-blooded animals. They belong to Mammalia because they have hair on their body and produce milk from mammary glands to feed their young ones. However, they lay eggs without giving birth to young ones. Laying eggs is characteristics of class Reptilia. Hence they form a link between reptiles and mammals. 

(A)Reptilia is a class of crawling animals where the members lay eggs.

Artiodactyla is an order possessing cloven-hooved mammals. Generally, they are ruminants but some non-ruminant members are Pigs and Hippopotamus.

Monotremes or Prototheria are mammals that do not give birth to live young ones. Instead, they lay eggs and nurse them after they have hatched. They have mammary glands but no teats. They simply pour milk onto their skin and it gets collected in a pouch where the babies can drink it from.

So the correct answer is 'Prototheria'.

Animals belonging to the subclass Prototheria lay eggs like non-mammals. But they feed their newborns with the secretions of their mammary glands. They are also called Monotremes as they have a single opening for both excretion and reproduction. There are only three surviving species of monotremes, spiny anteaters are one of them.

(A)Monotremes are the egg-laying mammals.

(A) Rodents are those animals whose incisors are continuously growing.

The ancestors of Mammals belong to Therapsida as there are various similarities seen in both of them which are mostly only seen in mammals.

Marsupial mammals are also known as pouch mammals. Due to very short gestation periods, the offsprings are poorly developed and are carried in the pouches till they develop. Macropus classifies as a Marsupialia due to these reasons.

Rhesus monkey, Gibbon, Gorilla, and Orangutan all have common ancestors with human beings. 

Ungulata contains Cattle, pigs, camels, deer, etc. All these animals are domesticated throughout the world.

Sea cows belong to the order Sirenia which is included in Mammals.

Prototheria includes Ornithorhynchus (Platypus) and all species of Echidna. This subclass once dominated the Australian continent.

Orangutan belongs to the family Hominidae which is the family of the great apes. General characteristics of this family are:

Mammals are warm-blooded animals. They have mammary glands. They are viviparous. They have hair or fur on their body. For example, dog, cat, dolphin, human, whale, etc. Psittacula is a bird. Manis is a genus of Pangolins. These are mammals of the order Pholidota. Planorbis is a Mollusca. Hydrophis is a type of snake.

Order Insectivora belongs to the Class Mammalia as they are small, furry mammals. Like all other mammals, they give birth to young ones, have mammary glands and diaphragm.

Bats belong to the order Chiroptera.

Though cloaca is not present in all mammals but it is found in monotremes or Protherians.

Cloaca is a chamber or cavity that acts as an exit channel in organisms like reptiles, birds and amphibians.

Humans belong to the Hominidae family.

The vast majority of mammals have seven cervical vertebrae (bones in the neck), including bats, giraffes, whales, and humans.

Mammals are viviparous, i.e. they give birth to young ones. But there are some exceptions. The monotremes like Echidna (Tachyglossidae) and Platypus (Ornithorhynchus) are oviparous mammals.

Rabbits belong to the order Lagomorpha.

Reduction division takes place during spermatogenesis. Spermatids and sperms will have haploid number of chromosomes.

Unlike other vertebrates, mammals nurse their young with milk produced by mammary glands. Though they're present in both males and females, in most mammal species mammary glands only fully develop in the females, hence the presence of smaller nipples on males (including male humans) also all mammals have hair at some point in their life. Not all mammals are land dwelling (dolphins)

Duck-billed platypus are egg-laying organisms. They are placed under the group of mammals because they possess skin with hair which provides protection and sweat gland which helps in the regulation of the body temperature and ionic balance. They possess milk-producing mammary glands which produce milk for the nourishment of the newborn. They show presence of seven cervical vertebrae and 12 pairs of cranial nerves like all other mammals. 

Bird flight is the primary mode of locomotion used by most bird species in which birds take off and fly. Flight assists birds while feeding, breeding, avoiding predators, and migrating. Bird flight is one of the most complex forms of locomotion in the animal kingdom. Some birds, are among the most intelligent animals; several bird species make and use tools, and many social species pass on knowledge across generations, which is considered a form of culture. In cooler weather, rather than increasing their metabolic rate, birds can save energy by using environmental heat to raise their body temperature passively. Birds have evolved the ability to maintain their body temperature at a somewhat lower level during periods of inactivity or in response to food deprivation.

Emu, flightless bird of Australia and second largest living bird: the emu is more than 1.5 metres (5 feet) tall and may weigh more than 45 kg (100 pounds). So, the correct option is 'Emu'

Sharks and bony fish are two fish groups. Sharks are cartilaginous fish. They have a cartilaginous skeleton. Bony fish have a skeleton made from calcified bones. Sharks and bony fish belong to the class Chondrichthyes and Osteichthyes respectively. This is the difference between sharks and bony fish. Bony fish also have an operculum. The operculum is a bony flap of skin over their gills that protects the gills. It opens and closes to help bony fish breathe when they are not swimming. Bony fish have scales, and most species have a fusiform body design.

Balaenoptera (Whale) and Delphinus (Dolphin) are aquatic mammals. Equus (Horse) and Felis (cat) are terrestrial and Pteropus (Flying fox) is a Prying mammal. So the correct option is A.

Amphibians and mammals have glandular skin, while reptilians and aves (except for preen gland at tail) have non-glandular skin. Hence, (b) is the correct answer, i.e., chameleon and turtle since both are reptiles.

Python is a large and non-poisonous snake. It kills its prey by coiling around and crushing before swallowing it.

Parrot belongs to the Class Aves whereas platypus and kangaroo belong to the Class Mammalia. Both ayes and mammals are homoiotherms, i.e., the temperature of their body remains constant irrespective of the temperature of the environment.

Salamandra belonging to the Class Amphibia has a tympanum that covers middle ear and in it fertilisation is internal. Ascaris has an unsegmented body and it belongs to the Phylum Aschelminthes. Pteropus is viviparous. Aurelia has a tissue level of organisation.

Amphibians have three-chambered heart, while reptiles have incomplete four-chambered heart (except crocodiles). Crocodiles, birds and mammals have complete, four-chambered hearts.

Rodents are gnawing mammal of an order that includes rats, mice, squirrels, hamsters, porcupines, and their relatives, distinguished by strong constantly growing incisors and no canine teeth. They constitute the largest order of mammals.

Animal development are the processes that lead eventually to the formation of new animal from cells derived from one or more parent individuals. There are various post-embryonic development that takes place outside the body and are considered as animal development.

The slope of the line is much steeper if we analyse the species-area relationships among very large areas like the entire continents. 

• Keratin is a protein deposited in the epidermal cells which protect the epithelial cells from damage or stress.
  
• It is an important structural material that makes up the hair, horns, claws, hooves, and nails etc.
  
• So, the correct answer is 'They are made of keratin'.

The Eutheria clad consists of the Placental Mammals.

Unidirectional flow means that air moving through bird lungs is largely 'fresh' air & has a higher oxygen content.  So, in bird lungs, more oxygen is available to diffuse into the blood. 

Maternal nutrition plays a vital role in the growth and development of the fetus. During prenatal development, the fetal circulatory system is integrated with the placenta via the umbilical cord so that the fetus receives both oxygen and nutrients from the placenta. The placenta is an organ that develops in your uterus during pregnancy. This structure provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. The placenta attaches to the wall of your uterus, and your baby's umbilical cord arises from it.

Metatherians or marsupials are mammals mostly found in Central and South America and in Australia. They include animals like bilbies, wombat, and kangaroos et cetera. In contrast to placental mammals, their scrotum develops in front of the penis instead of behind it. 

Snakes have leathery, soft or hard eggs laid on land or maintained inside the body until hatching. Salamanders have soft eggs normally laid in water or in damp media.

Marsupials have two vagina and two uterus and before birth a birth canal forms between them. The ancestors of marsupials are part of a larger group called metatherians and they represent the clade originating from the last common ancestor of metatherians. So, the correct option is 'Metatheria'.

• Baboon is an old world monkey belonging to the genus Papio
• Baboon is a very strong animal having sharp canine teeth
• They are well known for their intelligence

Metatherians are mammals that are also known as marsupials. Most of the marsupials are found in Central and South America and in Australia. They are called marsupials as they have a marsupium or pouch on their bodies. This group consists of animals like kangaroos, wombat, macropods, et cetera.

• Oviparous animals are the egg-laying animals which show little or no embryonic development within the mother.
• This type of reproductive method is common in most fish, amphibians, reptiles, birds and prototherians.
  
• Prototherians are egg-laying mammals and feed their newborn like all other mammals.  
• They lack nipples but the skin over their mammary glands secrete milk for their babies. 
• They are called monotreme as they have only one opening for excretion and reproduction. 
• So, the correct answer is 'Prototheria'.

Gorillas are ground-dwelling, herbivorous apes, they are the largest living primates, which are mammalian animals.

(A) Eutherian are mammalian clade consisting of Cretaceous. For example-Scaly anteater.

Opossum is the largest order of marsupials in West hemisphere containing 103 species. Metatherials are the mammalian clade that include all mammals closely related to marsupials.

Fishes have fins and gills which help them swim and breathe in water.

Order Primate contains Monkey and Man.

A. Eutherians are called placental mammals, in which the mothers carry their unborn.