A basic foundation in biology is important to any individual person because it's important to know about your own body (e.g. the reproduction topic as well as basic anatomy). It also explains the reasons why things happen (like why your heart rate increases after exercise) that can be key to every-day life.
It's important to society in general for so many reasons that I can't go into (but think genetically modified crops, life-saving medicines, even for understanding global warming etc.).
It's also important because of the skills it teaches you at GCSE: logic, accuracy, reasoning, making connections, drawing...
Hope this helps