The distinctive patterns and designs of the exine of pollen grains are characteristic features of:

Species of plants

The correct answer is: a) Species of plants

The distinctive patterns and designs observed on the exine of pollen grains are specific to different plant species. These patterns, often referred to as ornamentation, can vary in shape, size, arrangement, and sculpturing.

They serve as unique identifying features for each plant species. By examining the patterns and designs of pollen grains, scientists can differentiate between different plant species and classify them accordingly.

Therefore, the patterns and designs of the exine of pollen grains are characteristic features of plant species.