1. DIFFERENT CELLS PERFORM VARIOUS FUNCTIONS
Organisms can be classified by their cell type
Cells in multicellular organisms specialize
A multicellular organism is a community of cells
Scientists use models to study cells

2. Archaea & Bacteria Most organisms alive on Earth are unicellular.
At least 2-3 million BACTERIA live on 1cm2 of your skin
ARCHAE (means ancient) are similar to bacteria (but genetically different) and live even in thermal vents at 6000C.
Both bacteria & archaea are PROKARYOTES(no nucleus but a tough cell wall that protects them).

3. Eukarya
Eukarya cells have a nucleus; includes multicellular (plants, animals & fungi) and many unicellular (protists).
Are more complex and larger than prokaryote cells
Paramecium is an example of a complex unicellular eukaryote.

4. MULTICELLULAR CELLS SPECIALIZE
Multicellular organisms have many different types of cells that do different jobs.
SPECIALIZATION: when cells perform specific jobs for the organism, but can’t live on their own.
Blood cell can fight infection or carry O2, but can’t move body like muscle cells.

5. COMMUNITY OF CELLS Cells form members of a community.
TISSUE: a group of cells organized to do a specific job (nerve, bone, muscle, etc.)
ORGAN: different tissues working together to do a certain job.
ORGAN SYSTEMS: Groups of organs working together.
ORGANISM: highest level of organization.

6. Scientists use models to study cells
Scientists use many types of models to help them study cell structures.
DNA is the genetic material common to all cells. In 1950’s scientists knew what it was made of, but not how the parts fit together.
Rosalind Franklin used x-rays to make images of DNA.
James Watson and Francis Crick then put together a 3-D model of DNA in 1953.