Class Mammalia - Characteristic Features - Practice Questions & MCQ

• These are the vertebrates that possess hair and mammary glands.
• Mammals are endothermic or homoetherms or warm blooded
• They show the presence of external ear called pinna.
• The development of teeth occurs in the jaw socket (thecodont); teeth can be classified as incisors, canines, molars and premolars (heterodont); the milk teeth are replaced by permanent teeth (diphyodont).
• They have a four chambered heart with double circulation.
• Respiratory, excretory, nervous and reproductive systems are highly developed.
• Sexes are seperate and fertilisation is internal
• They are viviparus (except platypus) and development is direct
• 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).

The class Mammalia can be classified as:

Group Monotreme : 

• These are egg-laying mammals. 
• This group comprises of the platypus and two species of echidnas, or spiny anteaters. The shells of their eggs resemble that of reptiles. Monotremes have no teeth. 

Group Marsupials : 

• These are pouched mammals. 
• Australian marsupials include the kangaroo, koala, bandicoot, Tasmanian devil. 
• Most species of marsupials possess a pouch in which the very premature young reside after birth, receiving milk and continuing to develop.

Group Eutherians : 

• These are placental mammals. 
• All species possess a complex placenta that connects the fetus to the mother, allowing for gas, fluid, and nutrient exchange. 
• This group can be further classified as:

1. Insectivorous mammals
2. Rodents
3. Aquatic mammals
4. Carnivores and Ungulates