An example of organ level of organization is _______

Analyze the question: It asks which option is an example of the organ level of organization.

Concept: Living things are organized in increasing complexity:

Cell → Tissue → Organ → Organ system → Organism

• Cell: the basic unit of life (e.g., a spermatozoon, a red blood cell)
• Tissue: a group of similar cells doing the same job (e.g., xylem, phloem, muscle tissue)
• Organ: different tissues working together for a specific function (e.g., kidney, heart, leaf, stomach)
• Organ system: a group of organs working together (e.g., excretory system)
• Organism: a complete living individual (e.g., a bird)

Solution, option by option:

• A. Bird: a whole living thing, so this is the organism level. ❌
• B. Kidney: made of several tissues (epithelial, connective, and others) working together to filter blood and form urine. This is an organ. ✅
• C. Spermatozoon: a single specialized male sex cell, so this is the cell level. ❌
• D. Xylem: a plant tissue made of vessels, tracheids, and fibres that conducts water. This is the tissue level. ❌

Answer: B. Kidney.

Exam tip: Use the order "C-T-O-S-O" (Cell, Tissue, Organ, System, Organism). Ask yourself whether the item is a single cell, a group of similar cells, or a structure made of several tissues. Xylem and phloem are tissues, but the leaf, root, and stem are organs.