Hey there,
It means that, it is absorbed back into the blood after being filtered.
Hope this helps :))
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The question is asking to state the substance that come from the outside in the process of photosynthesis, base on my research and further investigation, I would say that its the heat or light energy. I hope you are satisfied with my answer and feel free to ask for more
The venus fly captures creaters with its mouth has indicatures that tell the plant too close quick which traps them