What would happen if the population of the bird species shown in the ecosystem in figure 4-1 were to suddenly decrease? •the grass population would increase •the fish population would increase •the fish would occupy the bird's niche •the grass and fish would compete for resources

The fish population would increase.

This is because if the number of birds decrease the number of  fishes would automatically increase as there would be less birds to eat the fishes.

According to trophic pyramid if the number of species at higher tropic level decreases the number of species at lower trophic level increases

answer: 4

explanation: 8