Algae is a primitive and ancient lower organism. The structure of algae is simple, and there is no difference in roots, stems and leaves. Most of them are single cells, colonies or multicellular bacteria. For example, Chlorella is a single cell, Volvariella volvacea is a colony, and seaweed is leaflike. Algae contain photosynthetic pigments, such as chlorophyll, which can carry out photosynthesis, and belong to autotrophs.
Bryophyte is a small higher plant, which does not differentiate true roots and vascular tissues and lives in a humid environment. Unique life history of dominant gametophyte generation. Sex organs (sperm organs and archegonium) and gametes (sperm and eggs) that produce gametes; Spores produce spores, but they cannot survive independently. They must rely on gametophytes to provide water and nutrition. There are about 23,000 species in the world, divided into liverworts, mosses and Ceratophyllum. Bryophytes play an important vanguard role in wasteland and disturbed secondary habitats; At the same time, it plays an irreplaceable role in soil and water conservation in the north temperate zone and alpine ecosystem. Plants such as peat have great value in garden and micro-landscape design, and are also widely used to monitor air pollution and as model plants for scientific research.
Pteridophyte, also known as pteridophyte, is a group of spore plants with the highest evolutionary level. Life history is the alternation of exotic generations with well-developed sporophytes. Sporophyte has the differentiation of roots, stems and leaves, and has primitive vascular tissue. The gametophyte is small, green and autotrophic, or has fungi, and the roots, stems and leaves are differentiated. Sexual reproductive organs are sperm organs and fallopian tubes of the cervix. No seeds. There are about 12000 species, which are distributed all over the world, especially in tropical and subtropical regions. Most of them are native, lithophytic or epiphytic plants, and a few are aquatic plants that like humidity or water, and they like wet and warm environment. There are about 2,600 species in China, mainly distributed in the provinces south of the Yangtze River. Generally, it can be divided into five subfamilies: gymnocarpinae, butterfly subfamily, lycopodinae, Dianthus heterophylla and silk fibroin subfamily. The first four subfamilies have primitive leaves, no petioles and leaf gaps, and only one vein, which is called lobular fern.
Seed plants, also known as flowering plants, are distributed all over the world and are the highest group in the plant kingdom. All seed plants have two basic characteristics, that is, they all have vascular tissues-phloem and xylem, which can produce seeds and reproduce with them.
Seeds can be divided into gymnosperms and angiosperms. The seeds of gymnosperms are naked, and their outer layers are not covered with pericarp. The seeds of angiosperms cover the pericarp.