Passive Movement Down Gradients

Steps:

• Define diffusion as the net movement of particles from high to low concentration without energy input.
• Define osmosis as the diffusion of water across a semi-permeable membrane from high water concentration to low.
• Compare both: they are passive processes requiring no cellular energy and occur down concentration gradients.
• Eliminate options: A requires energy (false), C limits to water (diffusion includes all particles), D limits to liquids (diffusion occurs in gases).

Why B is correct:

• Both follow Fick's law of diffusion, where net flux is proportional to the concentration gradient, driving movement from high to low concentration.

Why the others are wrong:

• A: Both are passive transport, requiring no cellular energy.
• C: Diffusion involves any particles, not just water; osmosis is specific to water.
• D: Diffusion occurs in gases, solids, and liquids; osmosis is in liquids but not exclusively.

Final answer: B