What is a body part that does a certain job for an organism called?

The correct answer is 'organ,' which refers to a specific body part that performs a particular function for an organism. In biological terms, organs are made up of tissues that work together to carry out specialized tasks necessary for the organism's survival and overall function. For example, the heart is an organ that pumps blood, while the lungs facilitate gas exchange.

The term 'function' refers to the specific role an organ plays in the larger system of the body, such as respiration or digestion, rather than identifying the physical body part itself. 'Structure' typically refers to the arrangement and organization of parts within an organism, but it does not specifically denote a body part responsible for a job. 'Cell' describes a smaller unit of life that makes up all living organisms but doesn't indicate an entire body part or organ that performs a specific function on a larger scale.