I thought those previous units were most important because it was all about how we were made and how others were made too.
The genetics was pretty cool because it showed there is many variations and varieties of all living things and how different things can be.
The matter and energy was also a key unit because it showed us how our bodies create energy using different chemicals to produce and break down used/unused energy.
I thought these were key because it was the main focus on how our body functions and how we were made.