<span>It is the variable in an experiment is not directly altered</span>
<span>When a plant undergoes photosynthesis, one of the by-products is oxygen or CO2.
Hope this helps !!! ^_^ !!!</span>
The Sun provides energy for the plants (producers) to grow. Herbivores (primary consumers) then eat the producers for energy. Any animals that eat the herbivores are considered secondary consumers. As this cycle continues, energy is lost to the environment as heat.
