The diagram shows a model of the movement of ions (represented by X) across a semipermeable membrane - HSC - SSCE Biology - Question 10 - 2012 - Paper 1

The process shown in the diagram is characterized by the movement of ions through a semipermeable membrane. This type of movement suggests a concentration gradient, where ions move from an area of higher concentration to one of lower concentration. Given the choices:

• Osmosis: This specifically refers to the movement of water across a semipermeable membrane, not ions.
• Filtration: This is typically driven by pressure rather than concentration gradients and is not applicable to ionic movement.
• Diffusion: This describes the passive movement of particles from high to low concentration, which applies here but lacks a focus on energy requirements.
• Active transport: This term refers to the movement of ions against their concentration gradient, requiring energy input.

Since the movement of ions across the membrane is being modeled without indication of energy use, the correct answer is therefore Active transport.