Why is it necessary to have the selective permeability of substances for a membrane ?

The table below shows the number of foot bones in some horse fossils.horse fossil recordhorse fossil number of foot bonesp 19q 17r 24s 13ancient horses had more bones in their foot then present-day horses. the present-day horse has 11 foot bones. what is the correct order of evolution of the horse starting from the youngest fossil? a. q p r s b. s r p q c. s q p r d. r p q s

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Why do oceanic plates tend to subduction when colliding with a continental plate