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Cell Structure
Section 3
Section 3: From Cell to Organism
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Bellringer
Key Ideas
Diversity in Cells
Levels of Organization
Body Types
Summary
Cell Structure
Section 3
Bellringer
What type of society would you prefer to live in: one in
which you must do everything for yourself, including
growing and gathering food, building shelter, etc., or one in
which each person does the job that they do best?
What are some advantages to having each person do a
specialized job?
What are some advantages to doing everything yourself?
Cell Structure
Section 3
Key Ideas
• What makes cells and organisms different?
• How are cells organized in a complex multicellular
organism?
• What makes an organism truly multicellular?
Cell Structure
Section 3
Diversity in Cells
• Both prokaryotic and eukaryotic cells can have a variety
of shapes and structures.
• The function of a cell is determined by its shape and the
organelles found in the cell.
• The different organelles and features of cells enable
organisms to function in unique ways in different
environments.
Cell Structure
Section 3
Diversity in Cells, continued
Diversity in Prokaryotes
• Prokaryotes can vary in shape, the way they obtain and
use energy, and their ability to move.
• Many prokaryotes have a flagellum, a long, hair-like
structure that grows out of the cell and enables the cell
to move through its environment.
• Prokaryotes may also have pili, short outgrowths that
allow the cell to attach to surfaces or other cells.
Cell Structure
Section 3
Flagella On Prokaryotic Cells
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Cell Structure
Section 3
Diversity in Cells, continued
Eukaryotic Cell Specialization
• Eukaryotic cells can vary in shape and external features.
• Depending on their function, eukaryotic cells can also
vary in their internal organelles. For example, muscle
cells, which use large amounts of energy, contain many
mitochondria.
• Animal and plant cells are two types of eukaryotic cells.
Both have many of the same organelles, but plant cells
also have chloroplasts, a large central vacuole, and a
cell wall.
Cell Structure
Section 3
Eukaryotic Cells
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Cell Structure
Section 3
Levels of Organization
• Plants and animals have many highly specialized cells
that are arranged into tissues, organs, and organ
systems.
• A tissue is a distinct group of similar cells that perform a
common function.
• An organ is a collection of tissues that work together to
form a structure which performs a specific function.
• An organ system is composed of a group of organs that
work together to perform major body functions.
Cell Structure
Section 3
Organization in Multicellular Organisms
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Cell Structure
Section 3
Body Types
• Unicellular organisms can thrive independently or live
together in groups.
• Cells that are permanently associated but do not work
together or integrate cell activities are called colonial
organisms.
• A multicellular organism is composed of many individual,
permanently associated cells that coordinate their
activities with each other. True multicellularity occurs
only in eukaryotes.
Cell Structure
Section 3
Visual Concept: Comparing Organisms
that are Unicellular and Multicellular
Cell Structure
Section 3
Body Types, continued
• In a multicellular body, cells are interdependent. Distinct
types of cells have specialized functions to help the
organism survive.
• The individual cells in a multicellular organism cannot
survive alone and are dependent on the other cells of the
organism.
• Must multicellular organisms begin as a single cell,
which divides to form more cells. These cells then grow
and become specialized in a process called
differentiation.
Cell Structure
Section 3
Visual Concept: Differentiation
Cell Structure
Section 3
Summary
• The different organelles and features of cells enable
organisms to function in unique ways in different
environments.
• Plants and animals have many highly specialized cells
that are arranged into tissues, organs, and organ
systems.
• A multicellular organism is composed of many individual,
permanently associated cells that coordinate their
activities with each other.