In which type of isolation do morphological structures prevent interbreeding?

Mechanical isolation occurs when differences in the physical structures of organisms prevent them from mating successfully. In many species, these morphological differences can include variations in size, shape, or reproductive organs that are incompatible with one another. For example, in certain insects, the shape of genitalia may differ so significantly that mating cannot occur, even if the species live in the same area. This type of isolation effectively prevents interbreeding between species, thereby contributing to the process of speciation, as it ensures that reproductive attempts are unsuccessful.

In contrast, gametic isolation involves the inability of sperm and egg to fuse due to incompatibilities at the gamete level, while behavioral isolation refers to differences in mating behaviors or rituals that prevent species from recognizing each other as potential mates. Hybrid inviability occurs when a fertilized egg develops into an embryo that cannot survive to maturity, rather than preventing mating outright.