In today's doodle, the ubiquitous Google logo morphs to depict, in turn, a polar bear in the tundra, a red fox in the forest, an elephant in the grasslands, a tortoise in the desert and an octopus in the ocean - with a different one appearing each time one visits the site's homepage.

"The vastness of the Earth's diversity makes it an intimidating topic, but in the end I chose to highlight the Earth's five major biomes," doodler Sophie Diao said in a blog post. On a day like this, we remember and celebrate our home in this great and stunning ecosystem.