Systematics is the branch of biology that classifies and organizes plants based on their evolutionary relationships, using characteristics like morphology, genetics, and biochemical traits. It helps establish plant taxonomy, grouping species into families, genera, and species. Plant diversity refers to the variety of plant species across different ecosystems, including vascular plants, bryophytes, and algae. Understanding plant diversity aids in conservation efforts, as many species face threats from habitat loss and climate change. Research in this field also explores the ecological roles of plants in sustaining life on Earth.