1. The Organization of Living Things
Chapter 4
Section 3

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