The human body and other organisms have five levels of organization: atoms, molecules, cells, tissues, organs, organ systems, and organism. Atoms combine to form molecules, molecules form cells, similar cells form tissues, tissues combine to form organs, organs that work together form organ systems, and all the organ systems combine to form the whole organism. The document then provides examples of the 10 major organ systems that make up the human body.

1. Levels of
Organization

2. 28.1 Levels of Organization
KEY CONCEPT
The human body and other
organisms have five levels of
organization.

3. 28.1 Levels of Organization
A. Levels of Structural Organization
Atom
Molecule
Cell
Tissue
Organ
Organ System
Organism

4. 28.1 Levels of Organization
Examples:
≈ carbon
≈ phospholipid
≈ nerve cell
≈ nervous tissue
≈ brain
≈ nervous system
≈ human
Atom
Molecule
Cell
Tissue
Organ
Organ System
Organism

5. 28.1 Levels of Organization
1. Atoms combine to form molecules
Atoms Molecule

6. 28.1 Levels of Organization
2. Molecules form cells
Molecules Cell

7. 28.1 Levels of Organization
a. Specialized cells develop from a
single zygote.
• Organisms are made up of specialized
cells.
red blood cell nerve cell

8. 28.1 Levels of Organization
• Zygotes first divide into embryonic stem cells.
• Stem cells develop in
two stages.
– determination, or
committing to
become one cell type
– differentiation, or
acquiring specialized
structures and
functions

9. 28.1 Levels of Organization
3. Cells form tissues
Similar cells with a
common function
form tissues
• There are 4 basic
tissue types:
• Epithelial
• Nervous
• Muscular
• Connective

10. 28.1 Levels of Organization
cell
4. Specialized cells function together in
tissues, organs, organ systems, and the
whole organism.
• Specialized cells perform specific
tasks.
• Tissues are groups of
similar cells working
together.
tissue
– epithelial tissue
– connective
tissue
– muscle tissue
– nervous tissue

11. 28.1 Levels of Organization
5. Tissues form organs
• Two or more tissue types form
an organ
An organ is a structure that
performs a specific function
for the body

12. 28.1 Levels of Organization
6. Organs form Organ Systems
• A group of organs which
work together for a common
purpose is an organ system
Brain, Spinal Cord, etc. Nervous System

13. 28.1 Levels of Organization
B. Body Systems
1. Integumentary System
Skin is the only organ
 Protects from injury
 Regulates body temperature
 Receptors for temperature, pain,
and pressure

14. 28.1 Levels of Organization
2. Skeletal System
Bones, cartilage, ligaments, and
joints
 Supports body
 Protection
 Storage for minerals (calcium)

15. 28.1 Levels of Organization
3. Muscular System
Muscles contract (shorten)
to cause movement
• Skeletal muscles are
large, fleshy, and attached to
bone

16. 28.1 Levels of Organization
4. Nervous System
Brain, spinal cord,
nerves, & sensory
receptors
• Responds to
irritants or stimuli

17. 28.1 Levels of Organization
5. Endocrine System
Releases hormones to control:
 Growth
 Reproduction
 Food use

18. 28.1 Levels of Organization
6. Circulatory System
Made of 2 organ systems:
 Cardiovascular System:
- Heart and blood vessels
- Transport oxygen, etc.
 Lymphatic System:
- Cleanses blood, immunity

19. 28.1 Levels of Organization
7. Respiratory System
• Nasal passages,
pharynx, larynx,
trachea, bronchi, lungs
Supplies body with
oxygen
Removes carbon dioxide

20. 28.1 Levels of Organization
8. Digestive System
• Mouth, oral cavity, pharynx,
esophagus, stomach, small
intestine, large intestine,
rectum
Breaks down food and
delivers nutrients to
blood for cells in the
body

21. 28.1 Levels of Organization
9. Urinary System
• Kidneys, ureters, bladder, and
urethra
• Removes Nitrogen-containing
wastes from the blood and
flushes them from the body in
urine
Regulates:
– Water balance
– Salt balance
– pH (acid-base) balance

22. 28.1 Levels of Organization
10. Reproductive System
Functions to produce offspring
• Male testes produce sperm
 Male Structures: scrotum, penis,
accessory glands, duct system
• Female ovaries produce eggs
 Female structures: uterine tubes,
vagina, uterus (where fetus develops)

23. 28.1 Levels of Organization
All of the organ systems form the organism