In a food web, two arrows indicating matter moving from producers to primary consumers represent the flow of energy and nutrients from plants or other producers to herbivores, which are the primary consumers.
The question addresses how matter moves in an ecosystem from producers to primary consumers. In a food web, producers, such as plants, utilize photosynthesis to produce energy-rich compounds. These producers are then eaten by primary consumers, which are often herbivores. The matter and energy stored in the producers are transferred to these consumers when they consume the producers.
In a food chain, we could illustrate this with a simple example: grass (producer) → rabbit (primary consumer). The arrow (→) shows the direction in which energy and nutrients flow, pointing from the organism being eaten (grass) to the organism that eats it (rabbit). This represents the transfer of energy and matter from one trophic level, the producers, to the next trophic level, the primary consumers.