Solution –  Ultrafiltration : it is a high pressure filtration through a semi permeable membrane in which the colloid particles are kept while the small size solutes and solvent are made to  move across the membrane by hydrostatic pressure forces .

Selective absorption : the glomerular filtrate coming in the renal tubule contains a lot material which is of use . As this filtrate  passes down the renal tubule , the usable substances are reabsorbed . Such absorption is known as selective absorption .