Penguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers. Most penguins feed on krill, fish, squid, and other forms of sealife caught while swimming underwater. They spend about half of their lives on land and half in the oceans. [1]Although all penguin species are native to the southern hemisphere, they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos Penguin, lives near the equator.
The largest living species is the Emperor Penguin (Aptenodytes forsteri): adults average about 1.1 m (3 ft 7 in) tall and weigh 35 kg (75 lb) or more. The smallest penguin species is the Little Blue Penguin (Eudyptula minor), also known as the Fairy Penguin, which stands around 40 cm tall (16 in) and weighs 1 kg (2.2 lb). Among extant penguins, larger penguins inhabit colder regions, while smaller penguins are generally found in temperate or even tropical climates (see also Bergmann's Rule). Some prehistoric species attained enormous sizes, becoming as tall or as heavy as an adult human. These were not restricted to Antarctic regions; on the contrary, subantarctic regions harboured high diversity, and at least one giant penguin occurred in a region not quite 2,000 km south of the equator 35 mya, in a climate decidedly warmer than today.
The etymology of the word "penguin" is highly disputed. The English word is not apparently of French, nor of Breton or Spanish origin (both attributed to the French word pingouin "auk"), but first appears in English or Dutch.Some dictionaries suggest a derivation from Welsh pen "head" and gwyn "white", including the Oxford English Dictionary, the American Heritage Dictionary, the Century Dictionary and Merriam-Webster, on the basis that the name was originally applied to the great auk, which had white spots in front of its eyes (although its head was black).
An alternative etymology, found in a few English dictionaries, links the word to Latin pinguis "fat", from its perceived appearance. This etymology would be improbable if "penguin" were found to have been originally applied to the great auk, as some sources suggest.
A third theory states that the word is an alteration of “pen-wing”, with reference to the rudimentary wings of great auks. This has been criticised for the unexplained nature of the alteration of the word.
The number of extant penguin species is debated. Depending on which authority is followed, penguin biodiversity varies between 17 and 20 living species, all in the subfamily Spheniscinae. Some sources consider the White-flippered Penguin a separate Eudyptula species, while others treat it as a subspecies of the Little Penguin; the actual situation seems to be more complicated. Similarly, it is still unclear whether the Royal Penguin is merely a color morph of the Macaroni penguin. The status of the Rockhopper penguins is also unclear.
