The landscape in which limestone is eroded to form deep valleys and cavers are called Karst landscape or karst topography. This kind of development start occuring whenever the acidic water starts breaking down the bedrocks near the cracks. As the bedrock starts breaking down slowly, the cracks start to open up creating bigger holes. with passage of time the holes will become big enough to create an underground drainage system for the surface water to flow and form underneath. If the water is unable to flow out and becomes stagnant, then the Karst will start getting bigger.
Answer: This is because animals (like humans) have more organelles to store in our bodies than bacteria. This makes sense because without all of our organelles we wouldn't be able to function properly. This is just another one of those form=function things.
-AnaMae10