Biological transmutation is like magic in nature! It is when living things, such as plants or animals, change one element into another element inside their bodies.
Think of it like when you make a cake! First, you mix eggs, flour, and sugar together. Then after you bake it, it becomes a cake! That's a bit like what biological transmutation is, except it happens inside living things.
For example, some plants can turn calcium (a mineral we need for strong bones) into potassium (a mineral that helps our muscles and nerves work properly). Animals, including humans, can also do this kind of "alchemy" - some fish change mercury (a poisonous metal) into a less harmful form.
Scientists are still trying to figure out how these living things use their magic powers to transmute one element into another. But we know that biological transmutation plays an important role in many natural processes, from photosynthesis in plants to detoxification in animals.