if a final spine something into something else, then that earthworm is a sink of that something else & caterpillar meat yellow animal pervert from oxygen oxygen and land and solar matter into rough and poison and space for themselves ->  photosynthesis is a source of oxygen  photosynthesis is a source of oxygen & animal perform student ->  plants are a source of oxygen through photosynthesis  plants are a source of oxygen through photosynthesis & a sink of something starling that something ->  plants produce oxygen through photosynthesis  plants produce oxygen through photosynthesis & if something is loss off of something , then something is the service of something -> plants give off oxygen through photosynthesis