Final answer:
Mammals are characterized by their efficient respiratory and circulatory systems, which support their high metabolic rates. They also have unique dental and skeletal adaptations, including heterodont teeth and specific jaw structures, as well as complex brains and social structures, contributing to their adaptability across various habitats.
Step-by-step explanation:
Distinguishing Features of Mammals
Mammals are a diverse group of animals with several distinctive characteristics which include the presence of hair or fur, sweat glands, and mammary glands. Another significant aspect of mammalian biology is their efficient respiratory and circulatory systems. These systems have adapted over time to support a constant, high-level metabolism that is characteristic of mammals. The respiratory system includes a set of lungs that allows for two-way air flow, which is different from the unidirectional flow seen in birds, but nonetheless highly efficient in facilitating gas exchange. The heart and lungs work together to keep cells well-supplied with oxygen and nutrients.
In addition to unique adaptations in their respiratory and circulatory systems, mammals also have specialized skeletal and dental features. They have heterodont teeth, which means they possess different types and shapes of teeth to allow them to eat a broad range of foods. Mammals include herbivores, carnivores, and omnivores. Their heterodont dentition with four types of teeth is quite effective in processing a variety of foods.
Mammals also have a relatively large brain and exhibit a high level of intelligence. They are capable of living in various habitats and forming complex social groups, which are seen as adaptive traits that have contributed to their success as a group.
Some features of their skeletal system are particularly unique to mammals, such as certain aspects of the jaw and the structure of the bones. These adaptations have allowed mammals to diversify and evolve into the roughly 5,200 species that we see today, including the groups known as monotremes, marsupials, and eutherian mammals.