Final answer:
Tendons consist of collagen fibers aligned in parallel, providing strength for muscle-to-bone connections, while ligaments have a mix of parallel and non-parallel fibers and elastic fibers that permit flexibility and stability in bone-to-bone connections.
Step-by-step explanation:
The difference in the organization of collagen fibers in tendons versus ligaments is that tendons have parallel fibers while ligaments do not always have all fibers parallel. Tendons consist of dense regular connective tissue with collagen fibers aligned in parallel to each other, which contributes to their ability to withstand tension and resist stretching in a single direction, essential for connecting muscles to bones. In contrast, ligaments also contain dense regular connective tissue but may have a mix of parallel and non-parallel fibers, allowing for somewhat more varied stress directions while connecting bones to bones. Additionally, ligaments contain some elastic fibers that contribute to their ability to return to their original length after being stretched, which is crucial for maintaining joint stability while allowing for movement.