How does the structure of the earth affect us?
I feel a bit guilty that I’ll only give you a partial answer, but here goes.
1) The unusually large core of the earth means we have a relatively strong magnetic field which protects us from many of the high energy particles emitted by the sun. These can (potentially) harm living organisms.
2) the core also has produced heat (from radioactive decay) over the entire history of the earth, driving the rock cycle via convection currents in the mantle. This means resources (think nitrogen, carbon, as well as metals etc) are recycled to the surface and the atmosphere has a relatively stable composition. This includes the ozone layer which defends us from high frequency e-m radiation (think of the negative effects of X-rays, gamma rays on living tissue.)
3) the destructive boundaries in the crust give rise to tall mountains which alter rain patterns and climate generally over large areas. They also provide a wide range of habitats for species to colonise.
Just three thoughts, but I feel sure a better answer will be along shortly!