1. The Structural Organization of Animals
   1. Anatomy
   2. Physiology
   3. Form fits function
      1. Cellular level
      2. Organism level
      3. Organ level
   4. Individual cells
   5. Tissues
      1. Epithelial tissue
      2. Connective tissues
         1. Loose connective tissue
         2. Adipose tissue
         3. Blood
         4. Fibrous connective tissue
         5. Cartilage
         6. Bone
      3. Muscle tissue
         1. Skeletal muscle
         2. Cardiac muscle
         3. Smooth muscle
         4. Involuntary muscle
      4. Nervous tissue
         1. Neuron
         2. Neuroglial cell
   6. Organs
   7. Organ systems
      1. Skeletal system
      2. Circulatory system
      3. Digestive system
      4. Respiratory system
      5. Muscular system
      6. Urinary system
      7. Reproductive system
      8. Endocrine system
      9. Integumentary system
      10. Lymphatic and immune system
      11. Nervous system
   8. The entire organism
2. Exchanges with the External Environment
   1. Digestive system
   2. Respiratory system
   3. Urinary system
3. Regulating the Internal Environment
   1. Homeostasis
   2. Negative and positive feedback
   3. Thermoregulation
      1. Endotherms
      2. Ectotherms
   4. Osmoregulation
      1. Osmoconformers
      2. Osmoregulators
   5. Homeostasis in the urinary system
      1. Circulatory system
      2. Kidneys
      3. Nephrons
      4. Urinary bladder
      5. Urea