An animated collapsible tree diagram maps the hierarchical classification of animals, from the root "Animals" down through Vertebrates and Invertebrates to specific phyla and classes. Using D3.js v3, the SVG renders nodes as circles with colored strokes and labels, while curved diagonal links connect parent-child relationships. The tree layout organizes data from a hardcoded JSON array, with interactive node clicks triggering smooth transitions that expand or collapse branches. Level-based colors distinguish taxonomic depth, and the visualization updates dynamically via D3's tree layout and diagonal path generators.