Final answer:
As the rainfall in a grassland biome decreases over time, the biome is likely to transform into a desert biome with lower net primary productivity and adapted plant and animal life.
Step-by-step explanation:
If an ecosystem in a grassland biome started to receive less and less rainfall every year, it is likely that the biome would gradually shift towards being a desert biome. Grasslands are known for their moderate precipitation and fire resistance due to the presence of perennial vegetation. However, as rainfall decreases, so does net primary productivity because plants have less water available for photosynthesis. The decrease in vegetation would result in fewer resources for herbivores, which might lead to a decline in their populations.
Desert biomes are characterized by very low precipitation and have flora and fauna that are adapted to such dry conditions. Since deserts typically have very little rainfall, the plants and animals that are present have adaptations like deep roots, water conservation strategies, and behaviors that minimize water loss. With continual declines in rainfall, the current grassland would slowly transition into a desert-like environment, given enough time and absence of human intervention to reverse the trend.
It is important to note that while fire is more common in grasslands due to their higher biomass and sometimes extreme temperatures, fire is less likely to be a major disturbance in a desert due to the sparse vegetation and thus reduced fuel for fires. Over time, the grassland ecosystem would undergo a transformation in its plant and animal life, adapting to the newer, drier conditions.