In nature there are many special relationships, called symbiotic relationships, between different species. In some of these relationships the partnership mutually benefits both parties; these partnerships are known as mutualism. Evolution's answer to mutualism is simply that these creatures evolved together, but that answer is not sufficient.
Consider the clown fish and the sea anemone. Sea anemone defend themselves by stinging with their tentacles, but clown fish have a special mucus that protects them from the sting. Clown fish find protection, then, living among the tentacles of the sea anemone, which in turn finds protection from the butterfly fish that eat anemones (and the anemone benefits by eating the waste from the clown fish). How did the special mucus evolve in the clown fish? After seeing other fish get stung, how did the clown fish figure out a recipe to protect itself? Did it magically get it right the first time, or was it stung repeatedly until it finally got the mucus right? And if evolution is true, why is the clown fish the only fish that has developed this beneficial mucus?
The crocodile and plover bird are another example. The croc is unable to brush and floss, and over time the build up of decayed food causes pain. Whenever he feels the urge, the croc will open his mouth wide and wait; when the plover sees the invitation it will land in the croc's mouth and pick out the food around their teeth. The bird gets a good meal and the reptile gets a good cleaning. The most unusual part of the relationship is that the plover flies safely away although nothing prevents the crocodile from eating the bird. Survival of the fittest should result in the bird becoming dinner, not a dentist. How did the first croc know all it had to do was open its mouth and wait for help? How did the first plover know it could trust the croc, safely feed from the croc, and that the croc sought its help to begin with?
These questions cannot be answered by evolution, but they do point to an intelligent Creator. His name is Jesus.
For by Him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through Him and for Him.