Levels of Biological Organization

Basic Biological Units and Systems

• The basic structural and functional unit of an organism is the cell.
• The urinary system is responsible for eliminating nitrogenous wastes and excess ions from the body.
• Organs are composed of two or more different types of tissues, with all four basic tissues represented: epithelial, connective, muscle, and nervous tissue.

Functions of Major Body Systems

• The cardiovascular system's primary function is to distribute oxygen and nutrients to all body cells while delivering wastes and carbon dioxide to disposal organs.
• The digestive system takes in nutrients, breaks them down, and eliminates unabsorbed matter as feces.

Metabolism and Waste

• Products of protein metabolism that are eliminated by the urinary system include urea, creatinine, and uric acid.

Fields of Study

• Neurobiology is the study of nerve cells.
• Endocrinology focuses on how hormones control body functions.
• Kinesiology studies changes in cell and organ functions due to muscular activity.
• Pathophysiology examines functional changes associated with disease and aging.

Respiratory and Excretory Functions

• The respiratory system takes in oxygen and eliminates carbon dioxide.
• The urinary system eliminates nitrogenous wastes and excess ions.
• The liver filters toxic substances from the blood.

Digestive Anatomy

• The small intestine consists of the Duodenum, Jejunum, and Ileum.

Cardiac Cycle

• The heart sounds are often described as "Lub" for contraction and "Dub" for the relaxation phase in the cardiac cycle.

Biological Responses

• The ability to sense and respond to stimuli is termed responsiveness.
• The increase in size of a body part or organism is known as growth.
• Cellular division for growth or repair is termed mitosis.
• The development of a cell from an unspecialized to a specialized state is called differentiation.

Test your knowledge about the levels of biological organization, from atoms and molecules to cells, tissues, organs, and organ systems. Learn about the basic structural and functional units of organisms and how different levels work together.