Final answer:
Latitude doesn't change during a hike up a mountain and doesn't account for the differences in biomes observed; instead, temperature, altitude, and precipitation are the main factors.
Step-by-step explanation:
An ecologist hiking up a mountain will observe changes in biomes due to variations in a number of abiotic factors. These changes are most notably due to shifts in temperature, altitude (or elevation), and precipitation (rainfall). However, the factor that doesn't change along the ecologist's journey up a mountain, and hence doesn't account for the differences in biomes, is latitude. Latitude is a constant that represents how far a location is from the equator and doesn't change as one moves vertically, such as hiking up a mountain. So, while factors like temperature and precipitation are crucial in determining the type of biome present at different altitudes, latitude remains consistent during the hike and does not contribute to the variation in biomes that the ecologist notices.