Cell SpecializationCh.37

The first cells were not specialized

• Organisms were unicellular

• The cell performed all cell functions

This cell has to get energy, get rid of its waste, & reproduce 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 neuron is specialized to do one job– receive & send messages.

Think of an analogy to compare and contrast unspecialized and

specialized cells.

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

How do cells become specialized?

What do you think happens?

An organism starts off as one cell. That cell divides by mitosis during development.

See… its already starting to look like something…

Fully developed Sea Urchin

Specialized cells develop from unspecialized STEM CELLS

When a cell divides, the new cells don’t get the same stuff

& cells can affect their neighbors

Each cell gets different chemicals

When a cell becomes specialized, some genes are turned on in that cell and others are turned off. If all of the cells expressed all of the genes in the DNA, the organism would grow up to be a blob.

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

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? How does structure relate to function?

These cells transport water through a plant (remember xylem?)