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Standard B-2.4Cell Differentiation
The student will be able to:
Explain the process of cell differentiation as the basis for the hierarchical organization of
organisms.
Cell Organization
Cell Differentiation
Stem Cells
Key Concepts
• 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.
It is essential for you to know:
Explain the process of cell differentiation.
Recall that all of the cells of a particularorganism contain all of the genetic code.
Summarize the unique characteristics of embryonic and adult stem cells.
TODAY’S OBJECTIVES:
How do we get from …..
ATOM to ANTONIO? (a person)
Organization Levels of Life
Atom to Organism
Nonliving Levels:
1. ATOM (element)
2. MOLECULE (atoms joining together to
create compounds like carbohydrates
& proteins)
3. ORGANELLES (nucleus, ER, Golgi …)
Levels of Organization
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)
Levels of Organization
Living Levels continued:6. POPULATION (one species in an area)7. COMMUNITY (several populations in
an area8. ECOSYSTEM (forest, prairie …)9. BIOME (Tundra, Tropical Rain
forest…)10.BIOSPHERE (all living and nonliving
things on Earth)
Levels of Organization
Nonliving levels…..
Atom ---------- Molecule -------
LIFE STARTS AT THE CELLULAR LEVEL!!
Organelles ------ Cell -------
Living levels
Tissue ------- Organs ----
Living levels cont’d…
Organ Systems ---- Organism
LIFE STARTS AT THE CELLULAR
LEVEL!
Let’s go back to where life started…
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
Now that we have learned how living things are organized, what’s next?
Prokaryotic vs. 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.
What’s the difference b/w prokaryotes and eukaryotes?
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)
Characteristics of Prokaryotes
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.
Characteristics of Prokaryotes
Are much smaller in size than the eukaryotic cells.
Very simple internal structure.
So what do these simple cells look like?
Characteristics of Prokaryotes
Prokaryotic cell
Most complex type of cell.
Appeared about 1 billion yr ago.
Generally more advanced than prokaryotes.
Nuclear membrane surrounds linear genetic material (DNA).
Characteristics of Eukaryotes
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
Characteristics of Eukaryotes
Eukaryotic Cell
How are they different?
PROKARYOTIC CELLS EUKARYOTIC CELLS
Organelles lack a membrane.
Ribosomes are the only organelles.
Genetic info floats around uncontained.
Organelles have a membrane.
Multiple organelles including ribosomes.
Genetic info is contained within the nucleus.
How are they different?
PROKARYOTIC CELLS EUKARYOTIC CELLS
Circular DNA Unicellular
Cells are small in size
Has large # of organisms
4 billion yr ago
Linear DNA
Uni- or multicellular
Cells are large in size
Has smaller # of organisms.
1 billion yr ago
Both:
◦Have cell membranes (outer covering of the cell)
◦Have ribosomes◦Have DNA◦Have a liquid environment within called the cytoplasm
How are they similar?
Cells Differentiate…..
Life Begins…
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)
Differentiation
As cells differentiate, they organize themselves into tissues, then organs, then organ systems.
Working together, the whole organism is complete.
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.
Not so fast, though….
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
Stem Cells
Found in embryos
Can give rise to any type of cell
You kill the embryo when harvesting embryonic stem cells
Very controversial
Embryonic stem cells
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.
Adult stem cells
Make a Venn Diagram showing the SIMILARITIES and DIFFERENCES between
Prokaryotic and Eukaryotic cells.
HOMEWORK: