Derived Characters of Mammals:
Derived characters are traits that evolved in a particular lineage and are not present in its ancestors. Here are some key derived characters of mammals:
1. Hair/Fur: This is the most defining characteristic of mammals. Hair provides insulation, protection from the elements, and aids in sensory perception.
2. Mammary Glands: Mammals are named after these glands, which produce milk to nourish their young.
3. Three Middle Ear Bones: Mammals have three tiny bones (malleus, incus, and stapes) in the middle ear that enhance hearing. This is a significant adaptation from their reptilian ancestors.
4. Neocortex: This part of the brain is responsible for higher cognitive functions and is much larger and more complex in mammals compared to other vertebrates.
5. Endothermy: Mammals are warm-blooded and maintain a constant internal body temperature, independent of external environmental conditions. This allows them to thrive in a wider range of environments.
6. Four-Chambered Heart: This efficient heart system ensures oxygen-rich blood is delivered to the body and deoxygenated blood is efficiently sent to the lungs.
7. Diaphragm: This muscle aids in breathing and allows for more efficient oxygen intake.
8. Specialized Teeth: Mammals have different types of teeth (incisors, canines, premolars, and molars) adapted for different dietary needs.
9. Live Birth: Most mammals give birth to live young, eliminating the need to lay eggs.
10. Viviparity: This refers to the development of young within the mother's body, providing protection and nourishment.
11. Complex Social Behaviors: Mammals often exhibit complex social structures, communication methods, and parental care.
12. Enhanced Sensory Perception: Mammals have well-developed senses of smell, touch, hearing, and sight.
13. Sweat Glands: These glands help regulate body temperature and prevent overheating.
These derived characters represent the evolutionary adaptations that allowed mammals to thrive in diverse environments and become one of the most successful vertebrate groups.