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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.