Across 3 bones which protect the lungs 5 organ where gas exchange takes place 6 scientific term for breathing in 7 a living thing 9 scientific term for breathing out Down 1 made up of many cells 2 group of organs working together to perform a function (5, 6) 4 group of similar cells working together to perform a function 7 group of similar tissues working together to perform a function 8 smallest functional unit in an organism