Five kingdoms divide life into categories based on shared characteristics. The kingdom Plantae contains around 250,000 species of plants, which are separated into nine phylums. Below phylums is the next grouping, called class. Classes are more specified than phylums, and are further broken down into groups called orders. Orders are then broken down into families, which are broken down into genera. The most specific grouping that plants belong to is known as species.
The plant phylum Cycadophyta is millions of years old, but only three families are alive today. These families are Cycadaceae, Strangeriaceae and Zamiaceae, all of which inhabit tropical or subtropical areas. These plants bear a resemblance to palms, and have leaves categorized as pinnately compound.
There exists only one genus of Equisetophyta, and it has 15 different species. These are non-flowering plants with a complicated structure of individual nodes and internodes on the shoots. These plants' leaves appear scaled as well as whorled.
The only surviving species of the seed plant phylum Ginkgophyta is Ginkgo biloba. It is a deciduous tree that lives in China and is commonly used as a street tree. Its leaves have a fan shape.
Seventy species of Gnetophyta are divided between three surviving genera. Thirty-five species belong to the genera ephedra, and are characterized by a shrubby look, stems that are jointed and scaled leaves. Thirty species are classified as Gnetum, and have big leaves with a leathery texture. The other five species belong to the Welwitschia genus and have unusual characteristics.
In this phylum of plants there is only one class, Lycopodiopsida, which contains three orders: Isotales, Lycopodiales and Selaginellales. There are many families, genera and species within these orders. Plants in the Lycopodiophyta phylum usually have underground stems, small, scaled leaves and no seeds or flowers. They reproduce using spores released from their leaves.
The Magnoliophyta phylum is the dominant group of plants on the planet, as it contains almost a quarter of a million species. These species belong to two classes: Magnoliopsida (dicots) and Liliopsida (monocots), although this is a division currently under debate. Because there are so many species of Magnoliophyta, they have widely varying characteristics. Some species are parasitic, some are aquatic and some are even carnivorous.
Nearly 550 species of plants can be classified as Pinophyta, or conifers. These species are split up among seven different families, which were all around during the Mezazoic era. These plants take the form of either shrubs or trees and reproduce using cones. Most species belonging to the Pinophyta phylum have needles or scaled leaves.
There are currently around 11,000 species of non-seeding plants belonging to the Polypodiophyta phylum. These species are split between 19 different families and have a diverse range of characteristics. Some common characteristics of these plants are true stems, roots and leaves. The roots are adventitious and the leaves are macrophylls and often exhibit an uncoiling pattern called circinate vernation.
Psilotophyta made up the entirety of conspicuous land plants on the planet during the Devonian period. These plants now grow only in tropical areas. The one family of Psilotophyta, known as Psilotaceae, has two surviving genera, Psilotum and Tmesipteris. Both genera do not have roots, only stems embedded in the ground with aerial branches attached.
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