In honor of Earth Day, today you have the chance to see one of five doodles every time you go to Google.com (just hit refresh for a new one). In a blog post on this year's drawings, doodler Sophie Diao says that she decided to do five to honor the Earth's major ecosystems: tundra, desert, coral reefs, grasslands, and forest. Within each, you see representative vegetation and animals that make the regions distinct, including a polar bear, fox, octopus, elephant, and tortoise.In past years, Google has often created just one doodle to mark an occasion. But today's multiple Earth Day iterations are a welcome reminder of the varied beauty that we may not see on a daily basis (skyscrapers are too often the norm), but that still exists and thrives across the earth.As Diao puts it , "Our planet — with its alternate scorching heat and bitter cold, its jagged peaks and deep trenches — may not always be kind to its inhabitants. Yet somehow the flora and fauna of Earth manage to thrive. On a day like this, we remember and celebrate our home in this great and stunning ecosystem."Click through to see all five images and check out the U.S. Environmental Protection Agency's Earth Day site to find ways to volunteer.