Answer:
A- producers provide energy to all of the other organisms. they directly supply energy to primary consumers (animals who eat plants). They indirectly supply energy to other consumers by feeding the animals that they eat. The energy gets transferred from the producers to the primary consumers, to the secondary consumers, and to the tertiary consumers.
B- aphids and slugs both eat producers. if the aphid population decreases, there will be less competition for the slugs to eat the their food.