Final answer:
A group of tissues working together forms an organ. This level is called the organ level of organization, connecting the cellular structure to larger systems within an organism.
Step-by-step explanation:
In the organization of the human body, tissues come together to form an organ. When several types of tissues successfully interact to carry out a specific function, they collectively make up an organ. This level of organizational complexity is higher than just an aggregation of cells forming tissues; it necessitates a more intricate cooperation between different tissue types.
For example, the stomach is an organ that includes muscle tissue to churn and mix food, epithelial tissue to line the stomach and protect it, and connective tissue to hold these structures together. Furthermore, each organ serves a distinct and vital role in the body's overall function. The organ level is thus a critical step in the hierarchy of biological organization, connecting the microscopic world of cells and tissues to the macroscopic world of organ systems and the organism as a whole.
Therefore, two or more tissues working together make up the organ level of organization.