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...What is a model models are conceptual representations used to explain and predict phenomena can be quite useful when the subject under study membrane in this case cannot observed directly scientific hypothesis that observations b future c realistic have limitations no possibly every detail of early cell although it could not light microscope biologists quickly grasped something must exist effectively separates inside from its external environment they also realized structure would more than simple barrier since obviously let some substances pass while blocked others moreover rate at which materials often varied over time gorter grendel read did add drawings for following boxes on whiteboard illustrate deduction information your notes observation...