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Cell Differentiation
Explain the process of cell differentiation as the
basis for the hierarchical organization of
organisms.
Cell Organization
Cell Differentiation
Stem Cells
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In the development of most multicellular
organisms, a single cell (fertilized egg) gives rise
to many different types of cells, each with a
different structure and corresponding function.
Nearly all of the cells of a multicellular organism
have exactly the same chromosomes and DNA.
Stem cells are unspecialized cells that continually
reproduce themselves and have, under
appropriate conditions, the ability to differentiate
into one or more types of specialized cells.
Explain the process of cell differentiation.
Recall that all of the cells of a particular
organism contain all of the genetic code.
Summarize the unique characteristics of
embryonic and adult stem cells.
ATOM
to
ANTONIO? (a person)
Atom to Organism
Nonliving Levels:
1.
ATOM (element)
2.
MOLECULE (atoms joining together to
create compounds like carbohydrates &
proteins)
3.
ORGANELLES (nucleus, ER, Golgi …)
Living Levels:
1.
CELL (makes up ALL organisms)
2.
TISSUE (cells working together)
3.
ORGAN (heart, brain, stomach …)
4.
ORGAN SYSTEMS (respiratory, circulatory,
digestive…)
5.
ORGANISM (you, frog, tree)
Living Levels continued:
6. POPULATION (one species in an area)
7. COMMUNITY (several populations in an
area
8. ECOSYSTEM (forest, prairie …)
9. BIOME (Tundra, Tropical Rain forest…)
10. BIOSPHERE (all living and nonliving things
on Earth)
Atom ----------
Molecule -------
Organelles ------
Cell -------
Tissue -------
Organs ----
Organ Systems ----
Organism
LIFE
STARTS AT
THE CELLULAR
LEVEL!


We will learn more about the lowest level or
organization: cells
What is the first thing that we need to know
about cells?
 All cells fall into one of the 2 major classifications:

PROKARYOTIC
or
EUKARYOTIC


Prokaryotic cells were here 1st and for billions
of years, they were the only form of life on
Earth. All prokaryotic organisms are
unicellular.
Eukaryotic cells appeared on Earth long after
prokaryotic cells but they are much more
advanced. Unlike prokaryotic organisms,
eukaryotic organisms can be uni- or
multicellular.

Simplest type of cell.

Oldest type of cell: appeared 4 billion yr ago.


Largest group of organisms. (more
prokaryotes than eukaryotes)
Unicellular organisms that are found in all
environments. (commonly called bacteria)


Prokaryotes DO NOT have a nuclear
membrane: have a single, circular
chromosome in a place called the nucleoid
region. (middle of cell)
DO NOT have membrane bound organelles:
have ribosomes to make proteins, but they
don’t have a membrane.

Are much smaller in size than the eukaryotic
cells.

Very simple internal structure.

So what do these simple cells look like?

Most complex type of cell.

Appeared about 1 billion yr ago.

Generally more advanced than prokaryotes.

Nuclear membrane surrounds linear genetic
material (DNA).

Eukaryotic cells have several different parts
which means they have a complex internal
structure.

Larger in size than prokaryotic cells.

2 main types of Eukaryotic cells:
 Plants
 Animals



Organelles lack a
membrane.

Ribosomes are the only
organelles.

Genetic info floats
around uncontained.

PROKARYOTIC CELLS
Organelles have a
membrane.
Multiple organelles
including ribosomes.
Genetic info is
contained within the
nucleus.
EUKARYOTIC CELLS
Circular DNA

Linear DNA

Unicellular

Uni- or multicellular

Cells are small in size

Cells are large in size

Has large # of
organisms


4 billion yr ago



PROKARYOTIC CELLS
Has smaller # of
organisms.
1 billion yr ago
EUKARYOTIC CELLS
Both:
◦Have cell membranes (outer
covering of the cell)
◦Have ribosomes
◦Have DNA
◦Have a liquid environment
within called the cytoplasm
All life begins with a single cell, a
fertilized egg called a zygote.


The fertilized egg
gives rise to many
different types of
cells in a
multicellular
organism.
Each cell has a
special shape and
job
(structure/function)


As cells
differentiate, they
organize
themselves into
tissues, then
organs, then organ
systems.
Working together,
the whole organism
is complete.

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
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Even though cells are differentiated, they
contain the same DNA in their nuclei.
During differentiation, only some parts of
that DNA are activated (turned on)
Since all cells have the same DNA, they all
have the potential to become any type of cell.
Once a cell specializes, it cannot be reversed.


A type of cell that is UNSPECIALIZED.
They have not yet differentiated into a certain
cell type.
◦ 2 types of stem cells:
 Embryonic stem cells
 Adult stem cells

Found in embryos

Can give rise to any type of cell

You kill the embryo when harvesting
embryonic stem cells
 Very controversial



Found in human adults.
Bone marrow can give rise to blood or bone
cells.
Not controversial b/c the human doesn’t die
when adult stem cells are harvested.
Make a Venn Diagram showing the
SIMILARITIES and DIFFERENCES between
Prokaryotic and Eukaryotic cells.
