This summer, you are returning to the research station in Costa Rica to follow up on the population of butterflies you have been studying. You are disappointed to find that there are fewer this year than last. In fact, at dinner your friends studying frogs and birds are complaining about the same thing. What type of influence do you suspect

it is likely that there was an environmental disturbance that affected the population density of the species.

Explanation:

All animals have their survival and reproduction capacity directly linked to environmental quality. This is because these animals take from the environment all the resources needed to live and develop. In this case, when the environment is balanced and has the necessary resources for life, animals can survive longer and develop well, being able to reproduce, generating more animals that increase the population density of their species. However, when this environment is disturbed, the animals' survival is threatened, even failing to reproduce. This lowers population density.

In the case presented in the question above, it is likely that populations of butterflies, frogs and birds are decreasing due to environmental disturbances.

"do a testcross with a homozygous recessive plant."