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

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).

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.

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.

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.

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.