Biology is very interesting, and the easiest of all the sciences, but that does not mean it's easy. The work you have to learn is not extremely difficult as long as you work hard and study - it's the exams. You will not pass by learning the material. You have to know how to apply the knowledge to unseen situations - believe me the exams will have ideas in that you could never have thought of, but you have to be able to transfer your knowledge.
As for chemistry, some parts are more simple, and others are a challenge - but it's really interesting and if you keep practicing you will get the hang of it. There is less application of ideas in chemistry, but it is probably more challenging than biology because you have to learn more content and it can get confusing at times.
Hard work - don't under-estimate that. Biology requires a lot detail to remember, and only do chemistry if you're doing well in maths!! They're good subjects and I enjoy them, but you have to be prepared to put the work in.