Why is it harder to determine which phenotype a person will have when a trait is controlled by many genes? APEX

Be in this im starting a with you so if you want you can get a partner for this. but basically im going to assign you guys a biome and you have to have a big sheet paper and you will turn it into 4 squares. the top right square is will be a drawing square for a drawing you will make of your biome. the top left square is about the biomes plants and drawings of them. the bottom left square is about the biomes animals. the bottem rights square is about the description of the biome. leave a comment or an answer and i will assign biomes. if your request one thats the one you get. send me a link to the project and i will grade ! im not a teacher btw.