diffusion and osmosis

2. concentration when molecules are less crowded
3. gradient A difference in the concentration of a substance across a distance.
8. concentration when molecules are more crowded
9. membrane a membrane (as a cell membrane) that allows some molecule to pass through but not others
12. a signal to which an organism responds
13. Diffusion of water through a selectively permeable membrane
16. a plants growth response to water; plant grows towards the water
17. response to earth's gravity, as the growing of roots downward in the ground
19. wall A rigid layer of nonliving material that surrounds the cells of plants and some other organisms.
20. A growth response of a plant toward or away from a stimulus

1. A growth response to light
4. tropism growth away from a stimulus
5. Movement of molecules from an area of higher concentration to an area of lower concentration.
6. organelle that stores materials such as water, salts, proteins, and carbohydrates
7. The drooping of leaves and stems as a result of plant cells becoming flaccid.
10. A state of balance
11. to limp
14. A growth response to touch
15. tropism Growth towards a stimulus
18. membrane A cell structure that controls which substances can enter or leave the cell.
19. A jellylike fluid inside the cell in which the organelles are suspended