1 â¢ Ozone (O3) is an extremely reactive gas molecule composed of three oxygen atoms. â¢ 2  Ozone forms in chemical reactions in the atmosphere when nitrogen oxides (NOx) and volatile organic compounds (VOCs), also called hydrocarbons (HC), come into contact with both sunlight and heat. â¢ Ozone (O3) is an extremely reactive gas molecule composed of three oxygen atoms. â¢ 2  Ozone forms in chemical reactions in the atmosphere when nitrogen oxides (NOx) and volatile organic compounds (VOCs), also called hydrocarbons (HC), come into contact with both sunlight and heat.
Grolar bears. The offspring of a grizzly bear and a polar bear, a grolar bear is one beast you don't want to meet in the woods. Interestingly, unlike many hybrid animals on this list, grolar bears are known to occur naturally in the wild.
When grizzly bear food is covered in snow during the winter, this species must den because there is nothing to eat. In contrast, most polar bears have access to their food of seals all winter long, so there is no need for them to den.