Cell Specialization

The first cells were not specialized Organisms were unicellular The cell performed all cell functions

This cell has to get its energy, get rid of its waste, reproduce, make everything it needs to make, regulate everything it needs to regulate, and do everything! All by itself!

Multicellular organisms have specialized cells Each cell has a specific job Cells have special shapes and structures that relate to function

This cell is specialized to do one job This cell is specialized to do one job. This is a neuron – it receives and sends messages. Notice the long thin extensions – these help connect this cell to other cells so that they can communicate with each other.

Think of an analogy to compare and contrast unspecialized and specialized cells.

How do cells become specialized? What do you think happens?

How do you get from one cell to a multi-cellular animal?

An organism starts off as one cell An organism starts off as one cell. That cell divides by mitosis during development. If all of the cells expressed all of the genes in the DNA, the organism would grow up to be a blob. But it doesn’t… Fully developed Sea Urchin See… its already starting to look like something…

Specialized cells develop from unspecialized STEM CELLS

When a cell divides, the new cells don’t get the same stuff Each cell gets different chemicals & cells can affect their neighbors

When a cell gets its job (becomes specialized), some genes are turned on in that cell and others are turned off. Not specialized Not specialized yet… Specialized! The “on” genes make their proteins which give the cell its special structures

Questions?

Your Turn - Write in Your Notebook: How are unicellular organisms different from multi-cellular organisms? How do cells in multi-cellular organisms become specialized? What is the advantage of being multi-cellular?

Cells are arranged to form multi-cellular organisms Tissues – made of cells working together Skin Connective Muscle Organs – made of tissues working together Heart Lungs Stomach Organ systems – made of organs working together Digestive system Endocrine system Circulatory system Organism – made of organ systems working together Human

Can you name some of the organ systems?

Good… because we will be learning more about them soon.

For now, tell me how you think this structure is related to its function: This is a cross-section of your intestines.

What about this: This is the lining of your wind pipe (trachea)

What about this: This is skeletal muscle.

What about this? How does structure relate to function? These cells transport water through a plant (remember xylem?)

On your notecard, write your name and… What did you learn today? What would you like to learn more about?