Answer - Well to put it in short terms.
Cells such as water cells or aquatic microorganisms need and required to have a large surface area increased. Because this helps them stay afloat without spending much amount of energy to float.
Jobs.... they do different jobs.
The anwer is DNA to your question
Your kidneys act like a filter to remove wastes and extra fluid from your body. Your kidneys filter about 200 quarts of blood each day to make about 1 to 2 quarts of urine