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Cellular Hierarchy
S7L2c
Explain that cells are organized into
tissues, tissues into organs, organs into
systems and systems into organisms.
Cellular Hierarchy
Cells (Least complex)
Tissues
Organs
Organ systems
Organism (Most complex)
Unicellular
• Only one cell
• The single cell carries out all life functions.
• Examples
– bacteria
– amoebas
Multicellular
•
•
•
•
Composed of many cells
Cells group together and divide labor
Cells become specialized for specific functions
Cells take on special shapes because of special
jobs
• Examples
– blood cells, nerve cells, liver cells, muscle
cells, skin cells
Tissues
• Cells grouped together to perform the same
function
• Four basic types in the body
– Epithelial tissue (skin, ducts, and tubes)
– Connective tissue (cartilage and blood)
– Muscle tissue (moves bones, digestive organs and
heart)
– Nervous tissue (carries messages)
Organs
• Several types of tissues grouped together
• Usually perform a complex task
• Examples
– Brain
– Heart
– Stomach
– Lungs
Organ Systems
• Several organs working together for a
particular function
• Examples
–Digestive system
–Circulatory system
–Nervous system
Examples of Cellular Hierarchy
Examples of Tissues
Examples of Organs
Examples of
Organ Systems
Epithelial
Skin
integumentary
Nerve
Brain
nervous
Connective
Heart
circulatory
Muscle
Biceps brachii
muscular