The levels of structural organization in living organisms describe how biological complexity builds from simple to complex structures.
Chemical Level
Atoms (e.g., carbon, oxygen) combine into molecules (e.g., DNA, proteins).
Example: Water (H_2O), glucose.
Cellular Level
Molecules form organelles, which compose cells-the basic unit of life.
Example: Mitochondria, nucleus, or a muscle cell.
Tissue Level
Groups of similar cells working together for a specific function.
Major types: Epithelial, connective, muscle, nervous.
Organ Level
Two or more tissues integrated to perform complex tasks.
Example: Heart (muscle + connective tissue), liver, lungs.
Organ System Level
Organs collaborating to accomplish major bodily functions.
Example: Digestive system (stomach, intestines, liver), nervous system.
Organism Level
All systems function together as a complete living entity.
Example: A human, tree, or bacterium.
Each level builds upon the previous one.
Emergent properties arise at each new level (e.g., consciousness emerges from neural networks).
Lower levels support higher levels' functions (e.g., cells → tissues → organs).
Collagen (chemical) → Fibroblast cell (cellular) → Tendon tissue (tissue) → Achilles tendon (organ) → Musculoskeletal system → Human (organism).