Here are the topics that bring an exposition of evolution of the plants and the own systematics, with a detailed study of the different groups of botanical plants; lastly one studies the botany as a science.

1 – From bacteria to flowers
2 – Plant Systematics
3 – Algae, fungi and lichens
4 – Bryophytes and pteridophytes
5 – Phanerogams
6 – The science of plants.

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Botany
1. From Bacteria to Flowers

Botany is the science that deals with the knowledge of plants or vegetables. These are distinguished from animals because they manufacture their own food using chlorophyll, green colorant.
But among primitive unicellular organisms, there is no noticeable difference between the vegetable and animal.
The family tree of plants gives us an outline of its evolution. Despite the comparative study of fossil plants and the living, the order of the branches of this tree is sometimes very insecure. The plants are older-celled aquatic organisms, whose evolution was less complicated than that of terrestrial plants. A large part of existing algae have not changed since its inception, millions of years ago.
The most important event in the history of plants was the appearance of multicellular, having a more complex constitution, which allowed them to adapt to a way of life more difficult. To survive on land, plants need a stronger constitution in order to compensate for the lack of water for sustenance, organs that absorb water from soil and air and reproduction methods suited to the new environment. This adaptation was first produced in plants of marshes and ponds and those that grow in coastal areas subject to tidal action, which needed to adapt to periods of drought during the low tide. These plants gave rise to the first terrestrial plants. During the Silurian period, the land started to become covered in a rich flora, which culminated in the gigantic species of ferns of the Carboniferous period.
In our day dominate the world plant seeds or plants with phanerogams, more complexly organized and, thanks to the “development” of the flower, are a safe method of reproduction on land, the pollen grain, very tough, it takes the cell male to female pistil, with minimal risk of extinction during transport or before fertilization. The great evolution of land plants led to the establishment of new vegetation. It also created new environmental conditions due to changes in climate and soil composition, the development of the animal world and especially to the man who, with their ability to use nature introduced many changes.

Phylogenetic tree of plants

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Botany
2. Plant Systematics

Plant Systematics: families, genera and species

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The practical knowledge increasingly detailed on plants and the need for scientific researches level these showed that the simple division into bushes and trees and grasses was insufficient. It then drew up a unitary system for identifying and classifying plants with greater ease, but it has also proved unsatisfactory.
The Swedish Linnaeus in the 18th century introduced the binomial system and was the first to develop a more complete classification of plants, which has validity today.
However, his sexual system of classification is artificial, since it relies only on external similarities.  Based on the theory of evolution and the laws of heredity emerged classifications on a natural system, whose criteria is the evolutionary kinship. The modern system affected the study of agriculture, forestry, pharmacology and other related disciplines.
Depth studies on the physiology and genetics of plants and plant ecology, these allowed the development of a systematic of plants, with defined groups. The basis of this classification is the species name attached to their gender. According to the binomial system introduced by Linnaeus, each plant has a Latin name, e.g. Rosa canina (wild rose), where the first name indicates the genus and the second the species.
Subsequent groups, from lower to higher level, are: families, orders, classes and branches. The main branches are thallophytes (covering the lower plants) and cormofitas (which are subdivided into bryophytes, ferns and seed plants or phanerogams), more evolved. The thallophytes bryophytes and ferns are plants with spores and so are called cryptogams. Plants with spores (small single-celled bodies) are reproduced through these that, without following a process of fertilization, develop new plants until the constitution. Phanerogams make it through male and female cells, which unite to form the embryo of the seed.
Not yet structured a definitive system of classification of plants, as each researcher differs in matters of detail, and appear continually changes due to new discoveries.

 

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Botany
3. Algae, Fungi and Lichens

Algae, Fungi and Lichens, by Ruth Miller (Author)

The algae, fungi and lichens are the different groups of plants with spores, whose unit is reduced to a vegetative thallus, namely that are not divided into root, stem and leaves.
It is difficult to give a scientific definition of these groups because of their scheme is still discussed.

Plants contain chlorophyll and can produce their own organic food. The plankton that makes up the basic nutrition of marine fauna is playing thus indirectly an important role in human nutrition.In Japan certain species of red and brown algae are used as food. At present, many researches are conducted with cultures of unicellular green algae, for food.

Fungi have no chlorophyll and many scientists consider them as special bodies: neither plants nor animals. Since they cannot produce their own food, must live as parasites on living matter or as saprophytes on dead organic matter. Some fungi are harmful to agriculture, for example, fungi and rusts. Food products may be attacked by mold. Many fungi, however, have a great importance in nature, as destroyers of organic matter, and some are beneficial, such as yeasts and certain by-products in form of drugs, as exemplified by penicillin. The fungi have at the bottom, a network of filaments, the mycelium, which are formed sporophores, responsible for the different ways they present.
Lichens are joint bodies composed of a fungus and an alga, living in symbiosis. It is known that algae contribute, by means of chlorophyll, with organic food, but the role of fungi is much discussed, it appears that the alga provides some sort of protection. To be born a new lichen, the fungal spore must find the right type of algae. Then germinates, forming a mycelium in which the filaments surrounding the cells of algae. Lichens grow very well, even in the most barren rocks. In more northern areas, develop large tracts of land or the bark of trees and shrubs. They do, however, very sensitive to gases and good indicators of air pollution and therefore are not observed in trees of large cities. Algae, fungi and lichens represent a third of all plant species known so far, but new discoveries are made constantly. Despite its apparent insignificance, this group of plants could play a prominent role as a reserve natural food, as algae and lichens would solve the problem of nutrition of the growing world population.

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Botany
4. Bryophytes and Pteridophytes

The evolution of higher plants developed through their adaptation to the needs of the earth’s environment. To them appeared organs that absorb water, supporting tissues and transport (stem) and systems for the exchange of gases with the air (leaves).

There are about some 400 million years ago, appeared the first terrestrial higher plants, the psilophyta, naked and without leaves, now extinct. Later came the bryophytes, lower state of terrestrial green plants, with rudimentary stem and leaves. They have no real roots nor channels for the movement of food and reproduce by spores, characterized by alternating generation: an individual asexual, sporophyte, produces another sexed, gametophyte, which, after playing itself, gives rise to another asexual individual, and so on. Among the bryophytes, the gametophyte that reaches the largest size is corresponding to the small stems and leaves of moss. Cell fertilized egg plant, asexual sporophyte grows, smaller: a capsule that produces spores that give rise to new gametophytes.
The bryophytes are found worldwide, especially in humid climates: tropical forests stricken by heavy rains, areas of forests and Nordic tundra. In Northern Europe and North America, there are vast tracts of bryophytes, predominantly sphagnum.
Pteridophytes comprise filicinae, lycopodiae and equisetaceae. These plants reached a degree higher than the evolution of bryophytes, because they already have roots, stems and leaves and have pots. Still reproduce by spores, generating alternating, but in them the sexual generation is very low. In the Carboniferous period, pteridophytes predominated: huge tree ferns, lycopods and equisetaceae formed the woods that later became deposits of coal-to-stone.
Today, classes of equiseti and lycopods and are reduced. The filicina constitute a group and slightly higher in the tropics, there are still some forms arborescent. Bryophytes and pteridophytes that still remaining have no great importance. Greatest utility in providing its predecessors extinct: the partially decomposed sphagnum peat provides, and the huge deposits of Carboniferous ferns have turned into coal-to-stone. Both are widely used as fuel for large heating value.

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Botany
5. Phanerogams

The appearance of the seed during the Devonian period was a decisive step in the evolution of plants. It is assumed that the first plants with certain types of seed were already missing pteridospermatophyta.
The mating system in phanerogams is more effective than in lower plants. The delicate spores require moisture and adequate light for germination, while seeds are more resistant, not dependent on the moisture and keep food reserves in its protective casing.
Phanerogams, also known as flowering plants, which are their reproductive organs, are more developed and numerous. They fall into two main groups: Gymnosperms (especially conifers) and angiosperms (trees and shrubs, as well as herbaceous plants). In gymnosperms, the seed has to be naked, while in angiosperms the carpel is enclosed. Gymnosperms, which are the oldest, achieved a great development during the Jurassic. The angiosperms appeared only about 60 million years.
The inflorescences of gymnosperms are very rudimentary: they have no perianth and the stamens and carpels, with its exposed seeds freely, often appear, meeting in cones. Authorities are still, in addition to conifers, some old ways, for example, cicad (palm garden) and Japanese ginkgo. The primitive welwitschia is an intermediate type between gymnosperms and angiosperms. Carpels in angiosperms are gathered in a pistil, whose bottom, ovary, houses and protects the egg. The flowers are bisexual most common presenting side by side stamens and carpels; some species, however, flowers have separate male and female into a single plant or different plants.
The pollen of the stamens is driven by wind, water or animals – mostly insects – even the carpel. The angiosperms are divided into monocotyledons (seeds with one cotyledon) and dicotyledons (seed with two cotyledons), the latter being more primitive than the first.

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Botany
6. The science of plants

The botany, plant science, covers all the knowledge that man met through the ages about the flora. Since primitive man, who learned to distinguish edible from poisonous species and learn about the healing properties of some herbs, such knowledge has been accumulated and passed it up to achieve a cultural complex. In ancient civilizations, the doctors were knowledgeable of the main plants. The Greek Theophrastus, the first to distinguish between monocots and dicotyledonous plants, is considered the father of botany. In medieval monasteries, the monks who cultivated medicinal plants have also brought their contribution. During the 16th and 17th century, botany was renewed by the researchers of Central Europe that, instead of copying old works, and drew new species found in books called herbals. With the evolution of plants knowledge, it became necessary a systematic classification and description. In the 18th century, Linnaeus laid the foundations of modern systematics of plants around the world and sent his disciples to gather unknown plants.
The improvement of the microscope led, during the 19th century, the formulation of cell theory and a considerable advance in plant morphology (study of the shape of the plants). The theory of evolution, Darwin, said new guidelines for botany, while Mendel’s laws of inheritance gave rise to modern methods of genetics and culture. Among other areas of botany, ecology, environmental studies of plants, taxonomy, classification, and plant physiology, their vital functions. The explanation of photosynthesis (plant capacity to produce organic substances by means of solar energy) and the discovery of DNA’s molecular structure and function in the cell nucleus were two equally decisive progresses for modern research of the plant kingdom.
This is therefore a very complex science, with many ramifications, only some of which were mentioned here. The modern botanical conducts theoretical and practical experiences with technical support and in close collaboration with related sciences.