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: