In biology, a blowhole is the hole at the top of a whale's head through which the animal breathes air. It is homologous with the nose of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. The exhale is released into the comparably lower-pressure, colder atmosphere, and any water vapor condenses. This is often visible from far away as a white splash. Main articles: Life All organisms (viruses not included) consist of cells, which in turn, are based on a common carbon-based biochemistry. ... Whales are not the largest species of exclusively aquatic placental mammals, members of the order Cetacea, which also includes dolphins and porpoises. ... Two or more structures are said to be homologous if they are alike because of shared ancestry. ... Human nose Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands...