2. phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. the plasma membrane is not, however, permeable to the enzyme. imagine a cell where phospholipid a is present in the layer of phospholipids facing the exterior of the cell, and phospholipid b is present in the layer of phospholipids facing the interior of the cell. after adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell

Phospholipase refers to an enzyme that cleaves the phosphate group from the phospholipids. In the given case, the phosphate group of phospholipid A is projecting towards the external part and the phosphate group of phospholipid B is present within the cell.  

As the enzyme is impermeable to the membrane, it will not possess the tendency to cut the phosphate from the phospholipid B. That is why it will only possess the tendency to cleave the phosphate group from phospholipid A and not from phospholipid B.  

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.