Final answer:
Geotropism is a force that affects certain organisms, causing them to grow or move in response to gravity. In plants, geotropism causes the roots to grow downward.
Step-by-step explanation:
Geotropism refers to the growth or movement of organisms in response to gravity. In the case of plants, geotropism causes the roots to grow downward. This is because specialized cells in the root caps detect and respond to gravity, ensuring that the roots grow into the soil.