Tag: classifications of chordata

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.