Final answer:
Plant-like protists, classified by evolutionary relationships, include autotrophic algae that lack true stems, roots, or leaves. Current classification schemes group eukaryotes into six monophyletic supergroups, emphasizing common ancestry.
Step-by-step explanation:
Classification of Plant-like Protists
The classification of plant-like protists is based on phylogenetics, which evaluates the evolutionary relationships among organisms. Contrary to traditional methods that categorized protists into groups based on similarities to plants, animals, or fungi, modern classification relies on genetic data. Plant-like protists, also known as algae, are autotrophic and capable of photosynthesis, much like plants; however, they lack true stems, roots, or leaves, distinguishing them from plants.
Examples of multicellular plant-like protists include seaweed and kelp, while single-celled examples include diatoms. Plant-like protists are essential to their ecosystems as primary producers, and some species exhibit a unique life cycle called alternation of generations. Despite the challenges of protist classification due to convergent evolution, the current effort is to organize all eukaryotes including plant-like protists into six supergroups based on a recent common ancestry, indicating that each group is monophyletic and descended from a single common ancestor.