Matter is conserved during the processes of photosynthesis and cellular
respiration by converting the raw materials into products during photosynthesis and again release the raw materials with the help of break down in the process of respiration.
Oxygen production of plants is different at different times of the day because of the presence of sunlight. Oxygen is produced in the process of photosynthesis which only occurs when the light is present. High light intensity leads to higher production of oxygen whereas no photosynthesis occur in completely dark environment because the stomata are closed and carbondioxide gas can't enter the plant body.
The tree produces food which eaten by greenfly. The ladybird feed on the greenfly and in the last the bird feed on ladybird.
The tree is present at the beginning of the model whereas the bird is present in the end because tree is a producer which converts solar energy into food molecules which can be eaten by different animals.
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