1. 7.4 Homeostasis and Cells

2. Homeostasis
Cells need to maintain a constant internal chemistry, size, shape, etc…. even though the surrounding environmental conditions change.
Homeostasis is the maintenance of a stable level of internal conditions, size, shape, etc…. and it requires cellular transportation.

3. Unicellular Organisms
Living organisms made up of only one cell

4. Multicellular Organisms
Living organisms made up of many cells

5. Cell Specialization
The cells of multicellular organisms are specialized for particular tasks and communicate with one another to maintain homeostasis.
Stem Cells

6. Levels of Multicellular Organization
Cells
Tissues
Organs
Organ Systems
Organisms

7. Cells are Organized into Tissues
A tissue is a group of cells alike in structure and function.
Skeletal muscle tissue
Cardiac (heart) muscle tissue

8. Tissues are Organized into Organs
An organ is a group of tissues which work together to perform a specific function.
Kidneys
Heart

9. Organs make up Organ Systems
An organ system is a group of organs working together to perform a specific function.
Digestive System
Circulatory System

10. Organ Systems make up Organisms

11. Cell Communication
The cells of multicellular can communicate using chemical signals, such as hormones.

12. Receptors and Communication
In order to respond to a chemical signal a cell must have receptors the signal molecule can “plug” into.