plants perform photosynthesis & photosynthesis is a source of oxygen ->  plants are a source of oxygen through photosynthesis  if something releases something else then that something is the source of that something else1 & if something releases something else then that something is the source of that something else2 ->  green plants are a kind of producer  green plants are a kind of producer & green plants are a kind of plant ->  plants are a kind of producer  plants are a source of oxygen through photosynthesis & plants are a kind of producer ->  producers are a source of oxygen  producers are a source of oxygen & if something releases something else then that something is the source of that something else ->  producers release oxygen  producers release oxygen & if something releases something else then that something is the source of that something else0 ->  oxygen is a kind of gas that is released by producers  an animal is a kind of consumer & an animal / bacterium requires oxygen for survival / to breathe ->  a consumer requires oxygen for survival  taking something in is a kind of method for obtaining something & if something requires something else then that something must obtain that something else ->  if something requires something else then that something can take in that something else  a consumer requires oxygen for survival & if something requires something else then that something can take in that something else ->  a consumer can take in oxygen for survival  a consumer can take in oxygen for survival & oxygen is a kind of gas at room temperature -> plants are a source of oxygen through photosynthesis0: oxygen is a kind of gas that consumers take in for survival  plants are a source of oxygen through photosynthesis0 & oxygen is a kind of gas that is released by producers -> oxygen is a kind of gas that is released by producers and taken in by consumers