I think that you should give your student a prize! The Sages of the Talmud ask the same question! They answer that every animal has a task to perform in the world, and there's something we can learn from each of them.
For example, say our Sages, we can learn modesty from a cat, and honesty and industriousness from an ant. Cats are basically shy animals and are discreet about taking care of their personal needs. Ants are hard-working, and they are "honest" in that they don't steal from each other.
King David tried to fathom the meaning behind each animal and he succeeded - with two exceptions! One was the spider and the other was the wasp. So, God showed King David very clearly the need for those two animals as well:
When running for his life from King Saul, David hid in a cave. King Saul and his soldiers were searching everywhere. God sent a spider to spin a web over the opening of the cave in which David was hiding. When the soldiers came to his cave and saw it was covered with a spider's web, they moved straight past it, not imagining that the web was freshly made!
On another occasion David entered secretly into King Saul's military camp at night. King Saul's general, Avner, turned over in his sleep and, unknowingly, trapped David with his legs. A wasp came and stung Avner, causing him to open his legs, allowing David to escape!
Another answer is that God made non-kosher animals in order to reward us for following the commandment not to eat them. And they can also serve as food for non-Jews!
