larger living things are made up of more cells than smaller living things & growth means size increases ->  if a living thing grows then the number of cells in that living thing increases  if a living thing grows then the number of cells in that living thing increases & if the number of cells in a living thing increases then more cells are produced in that living thing ->  growth requires the production of more cells  growth requires the production of more cells & cell division produces cells ->  growth requires cell division  growth requires cell division & if something causes a process then that something is required for that process -> cell division causes growth