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Biology
Chapter 7 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?
Diversity in Cells
 Prokaryotes
are always unicellular and
limited in size.
 Eukaryotes are often larger and can be
either unicellular or multicellular.
 Different organelles and features of cells
enable organisms to function in unique
ways in different environments.
Diversity in Prokaryotes
 They
can vary in shape, the way they
obtain and use energy, the makeup of
their cell walls, and their ability to move.
 To move they either use flagella (long,
threadlike structure) or pili (short, thick
outgrowths that allow them to attach to
surfaces)
Diversity in Eukaryotes




Animal and plant cells
Have many of the same organelles, but plant
cells also have chloroplasts, central vacuole,
and cell wall.
Structure varies according to their function.
Their internal makeup of cells are specialized
for certain functions. Example: muscle cells,
which use large amounts of energy, have
many mitochondria.
Levels of Organization
 Plants
and animals have many highly
specialized cells that are arranged into
tissues, organs, and organ systems.
Tissues
 Tissue:
a distinct group of cells that have
similar structures and functions.
 Example: muscle tissue is a group of many
cells that have bundles of cytoskeletal
structures.
Organs
 Different
tissues may be arranged into an
organ, which is a specialized structure
that has a specific function.
 Example: the heart is an organ made of
muscle, nerve, and other tissues.
Organ System
 Various
organs that carry out a major
body function that make up an organ
system.
 Example: The circulatory system is made
up of the heart, blood vessels, and blood.
Body Types
 Single
cells can not grow larger than a
certain size, multicellular organisms can
be large.
 A multicellular organism is composed of
many individual, permanently associated
cells that coordinate their activities.
 Distinct types of cells have specialized
functions that help the organism survive.
Cell Groups
 Some
unicellular organisms can thrive
independently, but others live in groups.
 Cells that live as a connected group but
do not depend on each other for survival
are considered colonial organisms.
Multicellularity
 True
multicellularity occurs only in
eukaryotes.
 The cells of a multicellular body perform
highly specific functions.
 Most multicellular organisms begin as a
single cell.
 The specialized cells are arranged into
tissues, organs, and organ systems,
making up the entire organism.