Trees, grass and cattle are examples of biotic factors in most savannas, while temperature, sunlight and soil composition are major abiotic factors. Specific factors are what determine the impact of biotic relationships and abiotic influences in a particular ecosystem. A typical study investigates the effect of tree density on grasses during a drought in the African savannas.
Scientists commonly make models that approximate the actions of abiotic and biotic factors as they occur in nature. Wildfires and soil fertility are examples of abiotic factors that affect the ground level plants in the Brazilian savanna. Fire reduces a plant's resistance to disease, while soil fertility increases plant growth. Interactions between ecological factors and the target species or habitat can be better understood when the model includes all biotic and abiotic factors at play.
Physical models include mesocosms, labs in the field that simulate ecological relationships using natural organisms and control structures. Evolutionary research requires conceptual models to approximate what occurs over geologic time frames. For example, the Red Queen model proposes that long-term evolutionary change results from the constant genetic adaptations to biotic factors, such as predation and competition for resources.
The Court Jester model suggests that abiotic events, such as temperature adjustments and earthquakes, lead to rapid genetic alterations for survival in a changed environment. Even when abiotic factors are evident, the genetic response can be massive enough to change the entire environment. The Red Queen and the Court Jester models work together to explain evolutionary change.