Levels of Organization

28.1 Levels of Organization

KEY CONCEPT The human body and other organisms have five levels of organization.

28.1 Levels of Organization

A. Levels of Structural Organization

AtomMoleculeCellTissueOrganOrgan SystemOrganism

28.1 Levels of Organization

Examples:

≈ carbon≈ phospholipid≈ nerve cell≈ nervous tissue≈ brain≈ nervous system≈ human

Atom

Molecule

Cell

Tissue

Organ

Organ System

Organism

28.1 Levels of Organization

1. Atoms combine to form molecules

Atoms Molecule

28.1 Levels of Organization

2. Molecules form cells

Molecules Cell

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

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

28.1 Levels of Organization

3. Cells form tissuesSimilar cells with a

common function form tissues

• There are 4 basic tissue types:• Epithelial• Nervous• Muscular• Connective

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

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

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

28.1 Levels of Organization

B. Body Systems1. Integumentary SystemSkin is the only organ

Protects from injury Regulates body temperature Receptors for temperature, pain,

and pressure

28.1 Levels of Organization

2. Skeletal SystemBones, cartilage, ligaments, and

joints Supports body Protection Storage for minerals (calcium)

28.1 Levels of Organization

3. Muscular SystemMuscles contract (shorten)

to cause movement• Skeletal muscles are large,

fleshy, and attached to bone

28.1 Levels of Organization

4. Nervous SystemBrain, spinal cord,

nerves, & sensory receptors

• Responds to

irritants or stimuli

28.1 Levels of Organization

5. Endocrine System

Releases hormones to control: Growth Reproduction Food use

28.1 Levels of Organization

6. Circulatory SystemMade of 2 organ systems:

Cardiovascular System:- Heart and blood vessels- Transport oxygen, etc.

Lymphatic System:- Cleanses blood, immunity

28.1 Levels of Organization

7. Respiratory System• Nasal passages,

pharynx, larynx, trachea, bronchi, lungs

Supplies body with oxygen

Removes carbon dioxide

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

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

28.1 Levels of Organization

10. Reproductive SystemFunctions 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)

28.1 Levels of Organization

All of the organ systems form the organism