Firstly you would isolate your two case study areas eg Alipne/Coral reefs within your introduction.
You would then explain that both involve a complex interaction of abiotic and biotic factors that make up the biosphere found - include examples of niche environments and the utiliastion of the lithosphere by biotic elements. Eg, how certain sea animals utilise their environment.
So a basic structure:
Intro-state your two environments/what the biophys interactions are/ how their interaction leads to diverse/functioning ecosystems
P1- Alpine, Outline biophysical environment/ describe the interactions that are occuring/produce examples of interaction
P2- Coral Reefs-Same basic idea
(maybe break each main para into two seperate)
Always address the question, take time to plan your respone (5mins), include a lot of data, make your response a logical progression and you should put yourself in the b6 range
hope it helps