The group of angiosperms formed over 125 million years ago. And there are still disputes about the specific period (era) of their occurrence. Some call the Cretaceous period, others speak of earlier dates, and others assure later ones.
One thing remains undoubted: this category of plants has taken a dominant position and settled in absolutely all parts of the globe, from tropical rainforests to hot and icy deserts of Africa and the Arctic.
What are they, angiosperms? Examples, features and properties of the taxon, the classification will be considered below.
Angiosperms: general characteristics
Representatives of this group received their name for the ability to cover the seeds with soft or hard tissues of the fruit. After all, in place of a flower, which is the visiting card of the taxon, the most diverse structures in shape and size, color and nutritional value are formed. They are called fruits.
The plant itself is a shoot that goes into the ground with a root system and has a flower, stem and leaves. A reproductive organ characterized by a special structure and allowingto adapt to any habitat and conquer new territories for settlement - this is the flower.
A more progressive structure, features and adaptations that appeared in the course of evolution made it possible to displace representatives of the gymnosperms, bryophytes and ferns. Today, the flora of our planet is dominated by beautiful, bright, 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 here. Briefly, we can say this: all plants that have a flower are angiosperms.
General floor 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 the angiosperms with the opportunity not to depend on water for the reproduction process was the flower.
Parts of a flower: stipules, receptacle, pedicel, corolla of petals, ovary, pistil, stigma, stamens. All of these structures are important as reproductive organs, as well as those that are further transformed into a fruit that protects the seed until full maturity.
People appreciate the flowers of plants 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, a flower is a useful important organ that saved them from water dependence duringbreeding time, because now it is done with the help of double fertilization. The fruits give protection and protect the seeds, and also participate in their dispersal when eaten by animals, this is also a big plus that distinguishes the structure of angiosperms from other plants.
The different structure of flowers, the variety of their forms allows you to increase the methods of pollination, which also contributes to the wide distribution and resettlement of plants.
Distinguishing Features
Of course, the most important and reliable innovation for flowering plants was the formation of a flower. However, not only this, but also other signs of angiosperms favorably emphasize and confirm their massive predominance among the representatives of the flora. Such as:
- The presence of a more perfect conducting system, including sieve elements of bast and phloem tissues. This allows you to more quickly transport the necessary minerals and water, as well as promote organic substances to the desired parts of the plant in order to store them further.
- Protection of seed structures by the pericarp, often the thick flesh of the fruit.
- Variety of pollination methods (wind, insects, animals, birds, self-pollination, cross-pollination and others).
- Reproductive organs (gametophytes) are able to develop quickly and easily, are under the 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 others to suppress their growth.plants.
- The structure of angiosperms implies their existence in different life forms - trees, shrubs, shrubs, semi-shrubs, herbs, lianas.
Such distinctive features make this group of plants very popular, hardy, adaptable and widely settled. And also necessary and important for a person and his economic activity.
Classification
There are over 250 thousand species of angiosperms, united in 13 thousand genera from 350 families. The taxonomy is quite numerous in terms of taxa and representatives.
The classification is based primarily on the classes of angiosperms, of which there are two:
- monocot plants;
- bipartite.
Each class is represented by a number of families, including different life forms and common in all territories.
Class Dicotyledons
Includes angiosperms, examples of which almost everyone has at home in the form of potted flowers. These are violets, begonias, spathiphyllums, ficuses. Of the garden plants, all Rosaceae and Solanaceae, Cruciferous and Butterfly, Compositae - rose hips, tomatoes, cucumbers, potatoes, cabbage, grapes, eggplant, buckwheat and many others. Among the woody forms there are also flowering plants, examples are oak, ash, maple, linden, birch, and so on. Economically important representatives, sources of valuable raw materials: cotton, flax, jute, hevea, cinnamon, hemp, laurel and many others.
Total Dicotyledons number over 170 thousand species, which is approximately 75% of all flowering plants. Their classification includes 360 families, united in 60 orders of 7 subclasses.
Distinguishing Dicots
There are a few main ones.
- The presence of two cotyledons (halves) in the seed. This can be seen especially well in the example of the seed of legumes. There are exceptions with one or 3-4 cotyledons.
- Type of root system: rod. Almost all these flowering plants have it. Examples on which this is easy to follow: peppers, hemp, nettles, begonias, spinach, and so on. Exceptions are for tree forms.
- The flower is almost all four- or five-membered. Rarely different.
Class Monocots
There are about 80 thousand different representatives united in families. Valuable angiosperms are numerous, examples of which are the following: all Cereals, Liliaceae, Amaryllis, Banana, Sedge, most palms. And this is not the whole list, because each family includes a large number of specific species representatives.
Grains 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.
Main features of Monocots
You can name a few key ones:
- root system - fibrous, rareexceptions;
- leaves lanceolate, elongated;
- three-membered flower, rarely four- or two-;
- the cotyledon in the embryo is one.
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 live.
