Memory Game Levels of organization LTOnline version Find the pairs. by Laura Quiroga Sánchez Organ: Made of similar tissues that work together to perform a specific activity or job. Organ system: Group of one or more Organs working together to perform functions for the organism. Organism: Entire living thing that carries out all basic life functions. Tissue: Made of several cells similar in structure and function that work together to perform a specific job. Cell: Basic unit of structure and function in an organism.