The group of angiosperms formed over 125 million years ago. And there is still debate about a specific period (era) of their occurrence. Some call the Cretaceous period, others speak of earlier dates, others assure of later ones.
One thing remains certain: this category of plants occupied a dominant position and settled on absolutely all parts of the globe, from tropical rainforests to hot and icy deserts in Africa and the Arctic.
What are they, angiosperms? Examples, signs and properties of a taxon, classification will be considered below.
Angiosperms: General Description
Representatives of this group got their name for their ability to cover seeds with soft or hard tissues of the fetus. Indeed, in place of the flower, which is the visiting card of the taxon, the most diverse structures are formed in form and size, color and nutritional value. They are called fruits.
The plant itself is an escape that goes to the ground by the root system and has a flower, stem and leaves. The reproductive organ, which is characterized by a special structure and allows you to adapt to any habitat and conquer new territories for resettlement, is the flower.
A more progressive structure, features and adaptations that appeared during the evolution made it possible to displace representatives of gymnosperms, bryophytes, and ferns. Today, the flora of our planet is dominated by beautiful, vibrant, diverse in life forms angiosperms. Examples of them can be given for a very long time, because there are more than 13 thousand births alone. Briefly, one can say this: all plants with a flower are angiosperms.
General building plan
The main organs that each representative of this group has are those that are characteristic of all higher plants: root, stem, leaves. An additional structure that provided angiosperms the opportunity not to depend on water for the propagation process was the flower.
Parts of the flower: stipules, receptacle, peduncle, corolla of petals, ovary, pistil, stigma of the pistil, stamens. All of these structures are important as reproductive organs, as well as those that are subsequently transformed into a fetus that protects the seed until it ripens.
People appreciate plant flowers for their extraordinary beauty and tenderness, pleasant aroma. Their healing properties are used, extracting useful extracts, grown in order to obtain juicy and tasty fruits in the future.
For the plants themselves, the flower is a useful important organ that saved them from water dependence during reproduction, because now this is done by double fertilization. Fruits provide protection and preserve seeds, and also participate in their dispersal when eaten by animals, this is also a big plus, highlighting the structure of angiosperms among other plants.
The different structure of the flowers, the diversity of their forms allows you to increase pollination methods, which also contributes to the widespread distribution of plants.
Features
Of course, the most important and reliable innovation for flowering was the formation of a flower. However, not only this, but also other signs of angiosperms favorably emphasize and confirm their mass predominance among representatives of the flora. Such, for example, as:
- The presence of a more advanced conductive system, including sieve elements of the bast and phloem tissue. This allows you to more quickly transport the necessary minerals and water, as well as promote organic matter to the desired parts of the plant for the purpose of their further storage.
- Protection of the seminal structures by the pericarp, often with the thick pulp of the fetus.
- The variety of pollination methods (wind, insects, animals, birds, self-pollination, cross-pollination, and others).
- Reproductive organs (gametophytes) are able to develop quickly and simply, are under reliable protection of the sporophyte plant itself.
- Biochemical composition of tissues. Many representatives contain toxic substances, alkaloids, flavonoids, phytoncides, and so on, which prevent animals from eating them and do not allow other plants to inhibit their growth.
- The structure of angiosperms implies their existence in different life forms - trees, shrubs, shrubs, shrubs, grasses, vines.
Such distinctive features make this group of plants very popular, hardy, adapted and widely spread. And also necessary and important for a person and his economic activity.
Classification
There are over 250 thousand species of angiosperms, combined in 13 thousand genera of 350 families. The taxonomy is quite numerous in taxa and representatives.
The classification is based primarily on classes of angiosperms, of which there are two:
- monocotyledonous plants;
- dicotyledonous.
Each class is represented by a number of families, including different life forms and common in all territories.
Class Dicotyledonous plants
Includes angiosperms, examples of which almost everyone has at home in the form of potted flowers. These are violets, begonias, spathiphyllums, ficuses. Of the gardening plants, all are Rosaceae and Solanaceae, Cruciferous and Moth, Compositae - rose hips, tomatoes, cucumbers, potatoes, cabbage, grapes, eggplant, buckwheat and many others. Among the woody forms there are also flowering plants, examples: oak, ash, maple, linden, birch and so on. Economically important representatives, sources of valuable raw materials: cotton, flax, jute, hevea, cinnamon tree, hemp, laurel and many others.
In total, dicotyledons account for over 170 thousand species, which is approximately 75% of all flowering. Their classification includes 360 families, united in 60 orders of 7 subclasses.
Distinctive features of dicotyledons
There are several main ones.
- The presence in the seed of two cotyledons (halves). This can be seen especially well with the example of a legume seed. There are exceptions with one or 3-4 cotyledons.
- Type of root system: core. Almost all of these flowering plants have it. Examples that can be easily traced are: pepper, hemp, nettle, begonias, spinach and so on. Exceptions are in wood forms.
- Almost all four-or five-membered flower. Rarely different.
Class Monocotyledonous
It has about 80 thousand different representatives, united in families. There are numerous valuable angiosperms, examples of which are the following: all Cereal, Liliaceae, Amaryllis, Banana, Sedge, most palm trees. And this is not the whole list, because each family includes a large number of specific species representatives.
Cereals are of great value in the human food industry. These include the most cultivated crops in the world: wheat, rice, barley, rye, corn and others.
The main features of monocotyledons
There are several key ones:
- the root system is fibrous, with rare exceptions;
- leaves lanceolate, elongated;
- a three-membered flower, rarely four or two;
- there is one cotyledon in the bud.
The classes of angiosperms and their numerous representatives form the diversity and beauty of the surrounding flora, which is so pleasant to admire and which gives us life. That's right, because oxygen is produced by plants, and without this gas, no animal can survive.