Question

what is the combined role of photosynthesis in the ecosystem?
to convert light energy into chemical energy and simple matter into complex molecules.
to help dead organisms decompose and return energy to the soil.
to transfer energy from animals to plants and break down matter.
to release energy into the atmosphere and create simple matter like water.

Explanation:

Photosynthesis is a biological process. In an ecosystem, plants (and some other organisms) use photosynthesis. The key aspect of photosynthesis is that it takes light energy (from the sun) and converts it into chemical energy (stored in molecules like glucose). This chemical energy is then used within the plant for its life - processes and also serves as an energy source for other organisms in the ecosystem (when they consume the plant).

Answer:

To convert light energy into chemical energy.