Chemical Level - interactions between atoms, which are tiny building blocks of matter; atoms combine to form molecules
Cell Level - the basic structural and functional units of plants and animals; molecules combine to form organelles (little organs), which are the small structures that make up cells
Tissue Level - a group of similar cells and the materials surrounding them
Organ Level - composed of two or more tissue types that perform one or more common functions
Organ System - group of organs that together perform a common function or set of functions and are therefore viewed as a unit
Organism Level - any living thing considered as a whole—whether composed of one cell, such as a bacterium, or of trillions of cells, such as a human
Integumentary System
Provide protection, regulate temperature, prevent water loss, and help produce vitamin D
SkeletalSystem
Provides protection and support, allows body movements, produces blood cells, and stores minerals and fat
MuscularSystem
Produces body movements, maintains posture, and produces body heat
Lymphatic System
Removes foreign substances from the blood, combats disease, maintains tissue fluid balance, and absorbs fats from the digestive tract
Respiratory System
Exchanges oxygen and carbon dioxide between the blood and air and regulates blood pH
Digestive System
Performs the mechanical and chemical processes of digestion, absorption of nutrients, and elimination of wastes
Nervous System
A major regulatory system that detects sensations and controls movements, physiological processes, and intellectual functions
Endocrine System
A major regulatory system that influences metabolism, growth, reproduction, and many other functions
Cardiovascular System
Transports nutrients, waste products, gases, and hormones throughout the body; plays a role in the immune response and the regulation of body temperature
Urinary System
Removes waste products from the blood and regulates blood pH, ion balance, and water balance
Female Reproductive System
Produces oocytes and is the site of fertilization and fetal development; produces milk for the newborn; produces hormones that influence sexual function and behaviors
Male Reproductive System
Produces and transfers sperm cells to the female and produces hormones that influence sexual functions and behaviors