Phylogenetic trees are significant in biology as they visually represent the evolutionary relationships among different species. These trees illustrate the common ancestry and divergence paths of organisms over time. By analyzing genetic, morphological, or behavioral traits, researchers can infer how species have evolved and adapted to their environments. Phylogenetic trees are crucial for understanding biodiversity and tracing the evolutionary history of specific groups. They also aid in fields like conservation biology, helping prioritize species for protection based on their evolutionary significance and vulnerability.