Question

What problems would you expect to observe in an ecosystem without primary consumers?

Answer 1

Many.

If you removed all the primary consumers from an ecosystem, there would be no way for energy to get from the producer (plant) level to higher level consumers which eat only primary consumers. So initially you would have see population increases in producer (and probably producer diversity) and decreases in secondary, tertiary and higher order consumer populations.

Answer 2

can yob help me with one more ?