• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue• Organ System: Group

of organs working together– Digestive System

• Organism: all organ systems working together

Muscle Tissue• Contracting cells• Skeletal, cardiac cells

Connective Tissue• Support the body• Bone, fat, tendons

Epithelial Tissue• protection sheet of cells• skin, stomach lining

Nerve Tissue• Transmit electric signals• Brain & Spinal Cord

• Zygote: fertilized cell created by the union of the egg and sperm

• Embryonic stem cells– Created during earliest

divisions– Potential to become

any type of cell

• Average human:– 100 trillion cells– Over 200 types of

human cells

Determination• Determination

– Stem cell genes program the cell to be a specific type

– Few weeks into development

– Irreversible

Differentiation

• Differentiation– Cells acquire the

structures & functions of a specialized cell

– Specific genes activated

Quick Questions• Do your muscle cells have the same DNA as your skin

cells?

Yes• Do your skin cells have the same DNA as your brain cells?

Yes• Do your brain cells have the same DNA as your liver cells?

Yes• So if all your cells have the same DNA, how do they know

to do different jobs?

Stay tuned for the answer

Stem cell programmed to become a muscle cell

Stem cell programmed to become a nerve cell

How will the top cell know to become a muscle cell…and the bottom to become a nerve cell if they have identical genes?

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

If they have the same genes…how does one become a muscle and the other a nerve?

Stem cell programmed to become a muscle cell

Stem cell programmed to become a nerve cell

ON ON ON

ON ON ON

During “differentiation”, certain genes are activated in some cells, but deactivated in others.

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

Remember that genes tell cells to create proteins. Muscle cells create different proteins from nerve cells based on the genes that are active and these proteins are what help the cell carry out their functions.

Programmed cell death

(apoptosis) between the

fingers

Webbed Toes

YouTube Review Video for help

Click here if the videoabove does not work.

1) What is a zygote?

2) What is the specific function of a stem cell?

3) How does “determination” differ from “differentiation”?

4) Cells are programmed to die during a process called ______.

5) From smallest to largest, name the 5 levels of organization.

6) Name the four types of tissues.

7) Which tissue is able to stretch and contract?

8) Which tissue transmits electric signals?

9) Which tissue covers and protects the body?

10) Which tissue connects the body?