All organisms are dependent for their food on producers, either directly or indirectly. So you find unidirectional flow of energy from the sun to producers and then to consumers. Is this in keeping with the first law of thermodynamics?

Energy flow in an ecosystem follows first law of thermodynamics. Using the grazing food chain as an example, For the harvest of solar energy by plants in the production of plant tissues, the first law of thermodynamics requires that the amount of solar energy captured by the plants remain the same before and after the transformation the energy involved cannot be created nor destroyed. For every thousand calories of solar energy captured and transformed by plant, there remain a thousand calories afterward.