Ch. 46
Differentiation and Specialization
See Pp. 905-907.
Unicellular organisms: One cell performs all functions
Multicellular organisms: all cells arise from three germ layers
of the embryo Individual cells perform only 1-2 functions.
Ectoderm (outer layer): forms
epidermis, inner surface of digestive tract and nervous system
Mesoderm (middle layer): forms
connective tissues (blood, bones, cartilage) and muscles
Endoderm (inner layer): forms
digestive and urinary structures, and glands
Tissues: Functional unit formed
from similar cells
1. epithelial: covers and lines body
2. connective: structural (bones, blood, cartilage)
3. muscle: provides for movement
4. nerve: conducts signals rapidly
Organ: Functional unit formed from
different tissues which work together.
Example: Heart, formed from cardiac muscle wrapped in connective
tissue, lined with epithelial tissue & interfaced with nervous tissue,
works to pump blood.
Organ System: Functional unit of
different organs which work together to perform a task.
Example: digestive system, contains eleven organs working to
catabolize food.
cell------>tissue--------->organ----------->organ
system---------->organism
Long & Slichter