Answer
a. Land plants and tiny water plants are the producers in the food web.
b. Heron, fox, and perch are the consumers in the food web.
c. Land plants → Slug → Diving beetle → Water fleas → Small fish → Perch
d. The small fish eats water fleas and tiny water plants.
e. The heron and the perch eat the small fish.
f. If all the frogs suddenly died, the population of the animals that eat frogs' prey, such as insects and small fish, could increase. This could lead to a decrease in the population of those prey species and a potential imbalance in the food web.