Final answer:
Mammals share characteristics such as being endothermic, having hair, giving birth to live young, nursing their young, and having blubber (in the case of marine mammals). Some marine mammals also have fins as adaptations for life in the water.
Step-by-step explanation:
Mammals
Mammals are a class of animals that share certain characteristics. All mammals, including marine mammals, are endothermic, meaning they generate their own body heat. They also have hair on their bodies, which helps to regulate their body temperature. In addition, mammals give birth to live young and nurse their young with milk produced by mammary glands.
Marine mammals, such as whales and dolphins, also share the characteristic of having blubber. This thick layer of fat helps them stay warm in cold waters.
While some marine mammals have fins, it is not a characteristic shared by all mammals. Fins are adaptations for life in the water and are only present in certain species, such as dolphins and whales.
Learn more about Characteristics of mammals