The movement of materials from a lower to higher concentration is called active transport.

Here's why:

* Active transport requires energy to move substances against their concentration gradient (from an area of low concentration to an area of high concentration). This is unlike passive transport, which doesn't require energy and moves substances down their concentration gradient.

Examples of active transport include:

* Sodium-potassium pump: This pump moves sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients.

* Glucose uptake by intestinal cells: Glucose is transported from the gut lumen into the cells, even when the concentration of glucose is higher inside the cell.

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