Multicellular organisms develop through cell differentiation and organization into higher levels. Cells form tissues, tissues form organs, and organs group into organ systems to carry out specialized functions. This allows organisms like humans to have different cell, tissue and organ types that work interdependently. Unicellular organisms rely only on single cells for all functions, while multicellular organisms gain benefits like larger size, longer life, and specialization through their organized cellular structure.
2. Key Concept As multicellular
organisms develop,
their cells differentiate
(change & separate)
and form levels of
organization
Why it Matters: so
Humans (we are
multicellular) can have
different kinds of cells,
tissues, organs, and
organ systems
3. Unicellular Organisms
“uni-”
= one
Prokaryotes are unicellular organisms
Some algae, some protists, and some
eukaryotes (yeasts), are unicellular
Can still do everything they need to stay alive
Benefits over multicellular organisms:
Need fewer resources
Can live in harsher conditions
4. Multicellular Organisms
“multi-” = more than one
Plants, animals, some protists, and most fungi
are multicellular
Start as a single cell many cells cells
differentiate (change) into different types of
cells cells group together
5. Multicellular Characteristics
Larger size = have less predators and have more
options of things to eat
Longer life – organism will continue to live even if
a single cell dies
Specialization – each type of cell has a specific
job, making the organism more efficient
6. Levels of Organization
1st Level: Cells
2nd Level: Tissues
3rd Level: Organs
4th Level: Organ Systems
Cells Tissues Organs Organ Systems
7. Level 1 : Cells
Cells can be specialized (have
a certain function)
Function = job
Function is related to the cell
structure
Structure = how parts of the
cell are put together
Shape
Material it’s made from
Structure of a brain cell is
different from muscle cell
8. Level 2: Tissues
Tissue = group of cells that work together to do a
specific job
Ex: Heart muscle tissue
is made of heart muscle
cells
Animals have 4 types of
tissue: nerve, muscle,
connective, protective
Plants have 3 types of
tissue : transport, protective, ground
9. Level 3: Organs
Organ = structure that is made up of 2 or more
tissues working together to get a specific job done
Ex: Stomach – muscle tissue moves food, special
tissues make chemicals to digest food, connective
tissue holds stomach together, nervous tissue
sends messages back and forth between the
stomach and brain
10. Level 4: Organ Systems
Organ system = group of organs working
together to perform a specific function
Each organ system has a specific job
Ex: Digestive system is made of several
organs including the stomach and intestines
11. Structure of Animals
Cells
-basic unit of an animal’s structure
-become specialized
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Tissues
-made of cells that work together to perform a specific function
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Organs
-made of different types of tissues that work together to perform a specific function
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Organ Systems
-made of organs that work together to perform a specific function
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Organisms