How plants are classified, from artificial systems to phylogeny, and the algae: their features, their reproduction, and the green, brown and red algae.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabPlants are classified to bring order to their huge variety. Early systems were artificial: they used a few easily seen characters, such as the number of stamens. Natural systems used many features, and phylogenetic systems use evolutionary relationships. Numerical taxonomy, cytotaxonomy and chemotaxonomy add numbers, chromosomes and chemicals.
Algae are simple, thalloid, autotrophic plants with chlorophyll, mostly living in water. They may be single cells, colonies like Volvox or filaments like Ulothrix and Spirogyra. They reproduce by fragmentation, by zoospores, and sexually by isogamy, anisogamy or oogamy. They fix much of the world's carbon dioxide and give food, agar and algin.
Algae are divided into three classes by their pigments and stored food. Chlorophyceae are grass green, store starch in pyrenoids and have cellulose walls. Phaeophyceae are brown with fucoxanthin, store laminarin or mannitol and have algin. Rhodophyceae are red with phycoerythrin, store floridean starch and reproduce oogamously.
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