Discovery of Oxygen. Oxygen was discovered in 1774 by Joseph Priestley in England and two years earlier, but unpublished, by Carl W. Scheele in Sweden. Scheele heated several compounds including potassium nitrate, manganese oxide, and mercury oxide and found they released a gas which enhanced combustion.
A polar bear’s head is oblong and relatively small compared to body size. The muzzle is elongated with a “Roman-nosed” (slightly arched) snout. Polar bears have 42 teeth, which they use for catching food and for aggressive behavior. Polar bears use their incisors to shear off pieces of blubber and flesh.