Organs are...

• A. Cells
• B. Tissues
• C. Organ systems
• D. Structures composed of specialized tissues and performing specific functions in plants and animals

Answer: (D)

An organ is a structure built from different tissues that work together to perform a specific function. Tissues are groups of similar cells that carry out related roles, and an organ combines several tissue types to carry out a task that none of the tissues could do alone. For example, in animals the heart uses muscle tissue to contract and pump blood, supported by connective tissue and nerves that coordinate the action. In plants, leaves, roots, and stems are made up of dermal, vascular, and ground tissues that collaborate to enable photosynthesis, transport, and support. The key idea is that an organ is a single functional unit composed of specialized tissues performing a defined role in both plants and animals.