1. Feedback
What is a feedback mechanism? A stimulus (hunger, pain, cold, fear, etc.) causes an organism to react to maintain homeostasis. Example: You eat a lot of sugar. Your blood sugar gets high. Your pancreas releases insulin to lower the blood sugar to a normal range.

2. Passive Transport
Passive transport means that the cell uses NO ENERGY to move substances in or out Substances move along a CONCENTRATION GRADIENT. This just means that molecules (water, sugar, salts, waste, etc.) move from where there is more to where there is less.

3. Passive Transport
Diffusion: movement of materials from a high concentration to a low concentration until equilibrium is reached Facilitated Diffusion: movement of materials through a protein channel with the aid of other molecules Osmosis: the diffusion of water

4. Facilitated Diffusion
Facilitated diffusion is not actually a type of diffusion but a type of transport process. It is passive because it does not require energy.

5. High solute = low water Low solute = high water
Osmosis
Hypotonic: low concentration of solute outside cell
Isotonic: concentrations of solute are equal
Hypertonic: high concentration of solute outside cell
High solute = low water
Low solute = high water

6. hypertonic

7. Tonicity: Animal Cells

8. Tonicity: Plant cells

9. Plasmolysis in onion cells
In Which Plants Dislike Hypertonic Solutions

10. And the moral of the story is…

11. Plants prefer hypotonic environments
Animals prefer isotonic environments

12. Graphic organizer

13. Practice problems