nisäkäslajien
Nisäkäslajien (Mammalia) are a class of animals characterized by several key features, including the presence of mammary glands, which are used for the production of milk to nourish their young. This class is further divided into several subclasses, including Prototheria, Metatheria, and Eutheria. Prototheria, also known as monotremes, are the most primitive group of mammals, including species like the platypus and echidnas. Metatheria, or marsupials, are characterized by their pouches, which carry and protect their developing young. Eutheria, or placental mammals, are the most diverse group, including humans, primates, and many other familiar mammals.
Mammals are endothermic, meaning they generate their own body heat, and they have a high metabolic rate.
The evolution of mammals began during the late Paleozoic era, with the first known mammal-like reptiles appearing