I love this question! There is no single answer, because “beauty is in the eye of the beholder”. In other words, different people find different things beautiful. To my eye, one of the most beautiful species is a bird called the azure-winged magpie. Take a look at this link to see how beautiful it is: http://www.surfbirds.com/gallery/search2.php?species=Azure-winged%20Magpie
The azure-winged magpie is actually quite a common bird in southern Portugal where I used to work. How amazing to have one of the world’s most beautiful species right outside your back door!
Of course the world is full of many other beautiful species, and I hope that you will take the opportunity to explore the planet over the course of your life. This can involve anything from going on an expedition, to your next family holiday or even just keeping your eyes open on the walk to school. Wherever you are in there world, there is always something new to see, and maybe you will find something even more beautiful than an azure-winged magpie!
Tough one! I work with baboons, not known for their beauty 🙂
I think the most beautiful things in nature are the amazingly extravagant things that evolve through sexual selection, like peacock feathers. Peacocks put a huge amount of energy into their feathers and have to be strong and healthy to grow them so impressively, so females can choose a healthy father for their offspring by judging the quality of the feathers. I think they’re amazing 🙂