Nutrients including sulfur and Phosphorus move through the ecosystem through a biogeochemical cyclic process. Chemical elements move via a pathway, that is termed as a biogeochemical cycle. Those move by means of the biotic and the abiotic components of the ecosystem.
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Explanation:
in dim light the iris contract ,the the pupils widens to allow more light to enter the eye,in bright light the iris relaxes and size of pupil becomes smaller to reduce amount of light entering the eye. NOTE: the muscle do not expand they either contract and relaxes
