Plants are divided into algae, fungi, ferns, bryophytes and seed plants, and seed plants are divided into gymnosperms and angiosperms, with more than 300 thousand species. Algae have not differentiated into real roots, stems and leaves in the plant kingdom, and can feed themselves by sunlight. The reproductive organs are a large group of single cells without embryonic development.

Plants have no differentiation of roots, stems and leaves, do not contain photosynthetic pigments such as chlorophyll (except a few photosynthetic bacteria), can not carry out photosynthesis, and can only live saprophytic or parasitic life, that is, heterotrophic health activities. Reproductive organs are mostly single-celled structures, and fertilized eggs will not become embryos.