Final answer:
The size and position of spots in Bicyclus anynana butterflies are genetically controlled and influenced by natural selection based on bird predation. Data from experiments show that birds respond differently to butterflies with or without eyespots, which affects natural selection.
Step-by-step explanation:
In Bicyclus anynana butterflies, the size and position of the spots on the undersides of their wings are controlled by genetic factors. However, these traits are influenced by natural selection based on environmental interactions, such as predation. Data from studies involving birds and butterflies with and without eyespots suggest that the eyespot pattern can affect butterfly survival. Eyespots may either help by mimicking a predator of the birds, thus deterring attacks, or hinder by making the butterflies more visible to predators. For instance, more birds responded to butterflies with eyespots, indicating that selection could be against this trait if it makes butterflies stand out. Conversely, the fleeing behavior of birds from butterflies with eyespots suggests that the trait might be favored in some contexts. This demonstrates that the response of one species can impact the natural selection process in another species, affecting traits such as eyespot size and position.