Let's imagine a pond where one can find algae, water lilies, water fleas, bleaks, pikes, and decomposer bacteria.

What would happen to the sizes of these populations, if

a) all the algae would die
b) all the water lilies would die
c) all the water fleas would die

d) all the bleaks would die
→ the water flea population would grow or
→ the water flea population would die out

→ the pike population would grow or
→ the pike population would become smaller