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Cell Specialization
Ch.37
The first cells were not specialized
• Organisms were unicellular
• The cell performed all cell functions
This cell has to get energy, get rid of its waste, & reproduce
all by itself!
Multicellular organisms have
specialized cells
• Each cell has a specific job
• Cells have special shapes and structures that
relate to function
This neuron is specialized to do one job– receive & send
messages.
Think of an analogy to compare
and contrast unspecialized and
specialized cells.
How do you get from one cell to
a multi-cellular animal?
How do cells become specialized?
What do you think happens?
An organism starts off as one cell. That cell divides by
mitosis during development.
Fully developed Sea
Urchin
See… its already starting to look like something…
Specialized cells develop from
unspecialized STEM CELLS
When a cell divides, the new cells
don’t get the same stuff
Each cell gets
different chemicals
& cells can affect their neighbors
When a cell becomes specialized, some genes are turned on in that cell
and others are turned off. If all of the cells expressed all of the genes in
the DNA, the organism would grow up to be a blob.
Not specialized
Not specialized yet…
Specialized!
The “on” genes make their proteins which
give the cell its special structures
Questions?
Your Turn - Write in Your
Notebook:
• How are unicellular organisms different
from multi-cellular organisms?
• How do cells in multi-cellular organisms
become specialized?
• What is the advantage of being multicellular?
Cells are arranged to form multicellular organisms
• Tissues – made of cells working together
– Skin
– Connective
– Muscle
• Organs – made of tissues working together
– Heart
– Lungs
– Stomach
• Organ systems – made of organs working together
– Digestive system
– Endocrine system
– Circulatory system
• Organism – made of organ systems working together
– Human
For now, tell me how you think this
structure is related to its function:
This is a crosssection of your
intestines.
What about this:
This is the
lining of your
wind pipe
(trachea)
What about this? How does
structure relate to function?
These cells
transport
water through
a plant
(remember
xylem?)