What is thought to bring different organisms such as fish and dolphins to have evolved a similar body plan?

their very similar environments.

Explanation:

The type of evolution that is referenced here actually has a name -- convergent evolution. It's when two types of organisms/species have nothing in common ancestor-wise but still evolve similarly due to their similar environments. The similar body plan the question is referencing could include fins and other "fish features" as well. :-)

glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.