When the effects of genes add up to make the phenotype, they are called additive genes.
Answer:
The example of direct interaction between two organisms is in coral reefs some fishes behave as a cleaner for the other fish.
Explanation:
The fish eats the parasites which harms the other fish. In this the cleaner fish gets food and the other fish gets rid of parasites. The example of indirect interaction between two organisms is when the birds eat the caterpillar, there is a positive impact on the plants because the Caterpillars used to the leaf of the plants.
The direct interaction between two organisms is defined as when the action of one organism has a direct impact on the other organism. The indirect interaction between two organisms is defined as when the action of one organism is responsible for indirect impact on the other organism.
Chirping, if that's what you mean.
