HOW DID YOUR BODY GET HERE?

Other cells

Cell Theory

ONE cell!

Zygote

Where do all cells come from? YOU started out as what?

Cells reproduce

therefore creating new

cells

How do multicellular living things grow?

Same size

But…

Different number

How do the cells of a human baby and human adult compare?

Cell reproduction

means cells divide.

…why don’t you

become gigantic?

How are new cells made

from old cells?

Let’s say your body produces up

to 96 million cells per minute…

Q: WHAT IS CELL REPRODUCTION?

A: In biology, reproduction is the production of a new

generation of individuals

Cells =

Individuals (unicellular organisms)

Fundamental structural & functional units of MULTICELLULAR

organisms

Cell division

Mitosis (Eukaryotes)

Binary fission (Prokaryotes)

This is an ASEXUAL process.

Many types of asexual reproduction in nature.

Q: ARE ALL THE CELLS IN YOUR BODY THE

SAME?

A: Many types of cells make up the body of a multicellular

organism.

Almost all of the cells in a multicellular organism are SOMATIC

CELLS.

“soma” = body

Somatic cells are normal BODY cells, not reproductive cells (egg cells

or sperm cells)

Somatic cells can be very different from each other.

~200 different types

Ex: muscle cells (myocytes), skin cells (epithelial cells), nerve cells

(neurons)

Q: DOES YOUR BODY CONTAIN THE SAME

EXACT CELLS YOUR ENTIRE LIFE?

A: All living things, including somatic cells, have a

lifespan.

WBCs ~ 13 days

RBCs ~ 120 days

Skin cells (top layer) ~ 30 days

Liver cells ~ 180 days

Old cells and dead cells must constantly be

replaced.

Q: WHAT HAPPENS TO DEAD CELLS?

A:

Some are shed

Skin, digestive lining

Some are digested by enzymes produced by

lysosomes.

Recycled materials

Q: HOW SMALL ARE CELLS?

A: Cell size in the living world varies

(2-200 µm)

Prokaryotes: 0.1 to 5 µm

Eukaryotes: 10 to 100 µm

Human body:

RBCs =

Skin cells =

Egg Cell =

Sperm Cell =

Q: HOW MANY CELLS DOES THE AVERAGE

HUMAN BODY (ADULT) HAVE?

A: Estimates have been given:

10 to 100 trillion cells

A study published in 2013 concluded the total number

for the standard human adult organism to be 37.2 trillion

cells.

Q: WHY DO MULTICELLULAR ORGANISMS EXIST? WHY

AREN’T HUMANS JUST ONE GIANT CELL?

A: Propose some possible answers!

Now… Let’s do some math! Yeah!