Fundamentals of plant taxonomy
There are more than 350 thousand different types of plants on Earth. Many of them are given folk names, for exampleplantain, dandelion, thistle, hops, swimsuit, lungwort . But such names are often incomprehensible to people of other countries. So,snowdrop different plants are named in different places:lungwort, anemone, scilla, crocus . The same plant is often called differently: Ukrainianscornflower calledhairy , buttercup - Zhovtets , potato Poles callcountrymen , and Belarusians -bulba .
To avoid confusion, biologists give Latin names to plants (as they do to all other types of organisms). They are understood by biologists all over the world.
To understand all the diversity of the plant kingdom allows a special area of biology -taxonomy . Systematic scientists distribute plants into groups, i.e. classify (organize)them, give names, produce a description of their properties, establish similarities and family ties between different plants. On this basis, they are combined into different groups: kingdoms, departments, classes, orders, families, genera and species.
Plant taxonomy
The basic unit of the plant system is view .
One species includes plants related to each other, similar in structure and life activity, capable of interbreeding and producing viable offspring similar to their parents.
Any species grows in certain conditions and occupies its territory on Earth - range (from lat. area - "area", "space").
Similar species are combined into childbirth , childbirth - in families , families - in orders and then follow classes and departments .
The species name consists of two words: black currant, red currant, Norway maple, Tatar maple, riverine maple etc. The first word, denoted by a noun, shows the plant belongs to the genus (currant, maple), and the second word, denoted by an adjective, is the specific name itself, showing its difference from other species of the same genus. So, black currant (Ribes nigrum) and redcurrant (Ribes rubrum) - two different species of the same genus - currant (Ribes). The word of the specific name is not used separately from the generic name, just as the adjective is not used separately from the noun. In the genus currant there are also species: golden currant, light currant, alpine currant, fluffy currant etc. They differ among themselves in the genus currant, and the specific word (adjective) emphasizes their dissimilarity.
Double, or binary (from lat. binarius - "double"), the names of species in the XVIII century. introduced by the Swedish naturalist Carl Linnaeus. In 1753 he published a great work."Plant Species", where he first used double (binary) designations of species.
Linnaeus had only a thirtieth of the plants known today. Therefore, his system was artificial - this was understood by its author himself. Linnaeus divided the entire plant world into 24 classes, depending on the number and location of stamens. He divided the classes into orders according to the number of pistils. Orders were divided into genera, and genera into species.
At present, when classifying, attention is paid to the vegetative and generative organs of the plant, and the structure of the reproductive organs plays a leading role. Scientists taxonomists describe now existing and extinct plants, give them names, determine their similarity and origin.
The species is the basic structural unit in the plant system, as well as in the system of all organisms.
Related species are combined into a genus. The generic name, denoted by a noun, can be used independently - currant, maple, birch, poplar. In this case, we are talking about a whole group of species and varieties that make up the genus, about their common generic properties. But the specific name is always used together with the generic name.
Close genera are grouped into families. Thus, the genera corn, wheat, rye, wheatgrass and many others are included in the same family - Cereals, or Bluegrass. The genera currant, gooseberry belong to the Gooseberry family.
Families are grouped into orders, and orders are grouped into classes. Among flowering plants, two classes are distinguished - Dicotyledonous and Monocotyledonous. The Dicotyledonous class includes the Gooseberry, Willow, Cruciferous, Poppy, and other families. The Monocotyledonous class is represented by the Cereal, Lily, Orchid, and other families.
Classes Dicotyledons and Monocotyledons form the department Flowering, or Angiosperms.
Bryophytes, Ferns, Flowering (Angiosperms) - different departments (types) of the plant kingdom.
A department is the largest unit in the plant kingdom.
Combines living organisms with characteristic features. All of them are autotrophs, that is, they can carry out photosynthesis. Also, all representatives of the plant kingdom have dense cell walls, the basis of which is such organic matter as cellulose. Starch in plants is a reserve substance. Despite the fact that saprophytic plants and parasites are characterized by heterotrophic nutrition, they belong to the plant kingdom, since this type of nutrition is secondary. There are other characteristic features of representatives of the plant kingdom. These are certain life cycles, ways of laying organs, an immobile lifestyle, etc. Although the above features are not common to all groups of plants, their combination makes it possible to distinguish plants, especially highly organized ones, from all living organisms of other kingdoms. At the lowest level of development, plants can easily be confused with the simplest animals. The main distinguishing feature of plants at this level is the presence of chloroplasts and features of the cell structure.
Scheme. plant classification
The higher the level of organization of plants, the more clearly the differences between them and other living organisms are noticeable. The majority of highly organized plants have a too dissected body, which causes an increase in its surface for better absorption of gases and liquids from the surrounding space in order to further convert them into nutrients during photosynthesis. The presence of a large number of specialized body parts in higher plants became possible precisely due to the division and differentiation of the body. Most of the significant features of the structure of plants are due to the characteristics of their reproduction, development and type of settlement.
The classification and systematic categories of the plant kingdom have undergone changes since the middle of the 20th century. Until that time, all plants were divided into lower and higher. The lower ones included bacteria, fungi, algae, lichens and slime molds, and the higher ones included bryophytes, rhinium, lycopods, psilots, horsetails, gymnosperms, ferns and angiosperms. To date, in the systematics of plants, there are bacterial kingdom and mushroom kingdom separately from each other. Therefore, the group "lower plants" has sunk into oblivion. In modern taxonomy, the plant kingdom is divided into three sub-kingdoms: real algae , scarlet(red algae) and higher plants (embryonic). These three sub-kingdoms include all the 350,000 plant species that grow on Earth. They vary in size - from very small to huge plants. All representatives of the plant kingdom differ from each other in life forms (herbs, trees, shrubs), the duration of the period of life (perennial, annual, biennial), requirements for environmental conditions, and types of reproduction.
Departments of the plant kingdom
All plants are classified into major divisions of the plant kingdom. These are mosses, club mosses, ferns, gymnosperms, horsetails and angiosperms (flowering) plants. Representatives of the department of angiosperms (flowering) plants, in turn, are divided into two classes - dicotyledonous and monocotyledonous. Different types of plant reproduction determine their division into seed plants and spore-reproducing plants. Taking into account the requirements of plants for growing conditions, heat-loving plants and cold-resistant, shade-tolerant and light-loving, drought-resistant and moisture-loving plants are distinguished. Those plants whose habitat is water are called aquatic.
The importance of plants on Earth is enormous. It is the representatives of the plant kingdom that are the primary producers of organic substances. It has been proven that all the oxygen available in the atmosphere appeared due to the vital activity of plants, or rather, photosynthesis. Plant communities are the natural habitat of animals and humans, while providing them with food, including indirectly, participating in the formation of soil. Plants serve as raw materials for the production of various technological materials, fuels, building materials, and medicines. Some plant species have become cultivated and valuable foodstuffs are obtained from them.
1. What is the fundamental difference between plants and other living beings?
They cannot move, they give off oxygen (the process of photosynthesis).
2. Using the drawing on p. 68 of the textbook, name the conditions necessary for plants for photosynthesis.
Water, carbon dioxide, solar energy.
3. What systematic groups are plants divided into? What specific plants belonging to these groups do you already know?
Species, genus, class, family, department, subkingdom, kingdom.
4. Where do algae live? What environmental conditions are decisive for their existence?
They live in the aquatic environment, fresh, salty water bodies, tree bark, moist soil areas. Algae live wherever there is even the slightest constant moisture from rain, fog, dew.
5. Tell us about the features of the external structure of multicellular algae.
They do not have real organs (leaves, stem, root), but the body of algae resembles their shape.
6. How is the algae cell arranged? What is common and how do cells of unicellular and multicellular algae differ?
The key difference is the number of cells that make up the body. The first on Earth appeared unicellular, and already from them multicellular creatures were formed. The level of organizations of unicellular primitive. Multicellular - more complex organized creatures.
7. What phenomenon is called the "bloom" of water? What algae causes it?
A sudden increase in the amount of algae growing in fresh water. Usually CYANOBACTERIA are involved in this phenomenon.
8. Name the algae that forms river mud.
ULOTRIX - Ulotrix. Cladophora - Cladophora. Spirogyra - Spirogyra.
9. What algae a person eats; used in the food industry?
Mostly marine, for example, sea kale.
10. Using additional sources of information (books, the Internet), prepare a report on algae living in extreme conditions - at low ambient temperatures, high pressure, etc.
Algae are able to reproduce and live in conditions that are not suitable for life for most living beings. For example, in conditions of temperature conditions reaching the boiling point, on snow and ice, in water with sub-zero temperatures.
Particularly resistant to extreme conditions are blue-green algae, the so-called cyanobacteria. They can live at temperatures ranging from 75-80 degrees C, and even a little higher.
Most algae are unicellular organisms. They are able to adapt quite easily to any environmental conditions. They have great survivability. They are also called filamentous life forms. They swim mainly on the surface of water bodies.
1. What kingdoms of the organic world do you know?
Bacteria, fungi, plants, animals.
2. What main groups of plants do you know?
Algae, mosses, ferns, horsetails and club mosses, gymnosperms, flowering plants.
Questions
1. Why is plant classification necessary?
To make it easier to understand the whole variety of plants, they were divided into groups.
2. What units of taxonomy do you know and what do they serve?
Related species are combined into genera, genera - into families, families - into orders, orders - into classes, classes - into departments, departments - into kingdoms. These groups combine plants with similar characteristics.
3. What are the features of the species?
Plants belonging to the same species are not only similar in structure and life activity, but during sexual reproduction they can produce fertile offspring and occupy a certain territory.
4. What is a grade? What is its difference from the species?
A variety is a group of plants of the same species, created by man and possessing certain economic characteristics and properties. Unlike plants of different species, plants of different varieties can interbreed.
5. By what signs can monocots be distinguished from dicots?
Plants belonging to one or another class differ in the number of cotyledons of the embryo, in leaf venation, in the nature of the root system of young plants grown from seeds, in the structure of stems and flowers.
6. What are the main features in the allocation of plants into families?
Families of angiosperms. Families are also distinguished on the basis of a set of features. The most important of them are the structural features of the flower and fruit.
Think
Why, when determining which class a plant belongs to, it is impossible to take into account only one trait?
However, it is not always possible to determine to which class a plant should be assigned using only one external sign.
For example, the raven eye has leaves with reticulate venation, but the embryo has one cotyledon, so it is considered a monocot plant. Plantain has an arcuate venation of leaves, a fibrous root system, but it is classified as a dicotyledonous plant, since the embryo has two cotyledons.
Thus, to determine whether a flowering plant belongs to one of the classes, it is necessary to know all the features of this plant.
Tasks
Using figure 114, highlight the features characteristic of dicotyledonous and monocotyledonous plants.
If a plant has an embryo with two cotyledons, reticulate leaf venation, a tap root system, vascular bundles in the stem are located in the center or in a circle, and the number of flower parts is a multiple of four or five, it is classified as dicotyledonous. The vascular bundles of dicots tend to have cambium, and the bark and pith are usually well differentiated.
If the embryo of a plant has one cotyledon, leaves with parallel or arcuate venation and a fibrous root system, vascular bundles in the stem are arranged “randomly”, and the number of flower parts is a multiple of three (3 sepals, 3 petals, 6 stamens), it belongs to the class of monocots. In monocots, vascular bundles are usually devoid of cambium. They do not have a clearly differentiated cortex and pith.
All plants that exist on the planet are so numerous and diverse that scientists have repeatedly tried to systematize them. To this end, they divided the representatives of the flora into different species and groups. This kind of sorting is based on their main characteristics. In our article, a systematic classification of plants will be given. In addition, their main features and structural features will be indicated.
examples and signs
First of all, it is worth saying that plants are organisms capable of autotrophic nutrition. They independently produce organic matter - carbohydrate glucose in the process of photosynthesis from carbon dioxide and water. This process occurs in chloroplasts - green plastids. But on one condition: if there is sunlight. The biological name for this action is photosynthesis. This is the main feature that characterizes the plant kingdom, the classification of which is based on the features of their structure within the framework of the evolutionary process. Its founder is Jean-Baptiste Lamarck, who introduced double (binary) species names. The classification of plants (table with examples) is given at the end of our article.
lower plants
The first and most primitive plants that arose in the process of evolution are algae. They are also called inferior. It is also a systematic classification of plants. Examples of this group: chlamydomonas, chlorella, spirogyra, kelp, sargassum, etc. Lower plants are united by the fact that their body is formed by individual cells that do not create tissues. It is called thallus or thallus. Algae also have no roots. The function of attachment to the substrate is performed by filamentous formations of the rhizoid. Visually, they resemble roots, but differ from them in the absence of tissues.
higher plants
Now consider the types of plants, the classification of which is based on the complication of the structure. These are the so-called first land migrants. For life in this environment, developed mechanical and conductive tissues are necessary. The first land plants - rhinophytes - were small organisms. They were devoid of leaves and roots, but had some tissues: primarily mechanical and conductive, without which the life of plants on land is impossible. Their body consisted of aboveground and underground parts, however, instead of roots, there were rhizoids. Reproduction of rhinophytes occurred with the help of cells of asexual reproduction - spores. Paleontologists claim that the first higher land plants arose 400 million years ago.
higher spore plants
The modern classification of plants, examples of which are given in the article, involves the complication of their structure due to adaptation to changing environmental conditions. Mosses, club mosses, horsetails and ferns are among the first terrestrial organisms. They reproduce with spores. In the life cycle of these plants, alternation of generations is observed: sexual and asexual, with the predominance of one of them.
higher seed plants
This vast group of plants includes organisms that reproduce generatively with the help of a seed. It is more complex than disputes. The seed consists of an embryo surrounded by a reserve nutrient, and a peel. It protects the future organism from adverse conditions during development. Thanks to this structure, the seed is more likely to develop and germinate, although certain conditions are needed for this: the presence of heat, a sufficient amount of solar energy and moisture. This group combines two divisions: holo - and angiosperms.
Gymnosperms
The characteristic features of this division is the absence of flowers and fruits. Seeds develop openly on the scales of cones, that is, naked. Therefore, the plants of this group received such a name. Most gymnosperms are represented by conifers. They are characterized by the apical growth of the shoot, the presence of special passages filled with resin and essential oils. The needle-like leaves of these plants are called needles. Their stomata are also filled with resin, which prevents excessive evaporation and unwanted moisture loss. Therefore, most conifers are evergreen. They do not shed their leaves with the onset of the cold season. Cones of all gymnosperms are not fruits, because they do not form flowers. This is a special modification of the shoot, which performs the function of generative reproduction.
Angiosperms
This is the largest group of plants that are the most complex. They currently dominate the planet. Their characteristic features are the presence of flowers and fruits. in turn, it is divided into two classes: mono- and dicotyledonous. Their main systematic feature is the corresponding number of cotyledons in the seed embryo. A brief classification of plants, examples and main features of the structure of the main systematic units are given in the table. It illustrates the complication in the structure of organisms in the process of evolution.
Plant classification: table with examples
All representatives of the flora can be systematized. Let's summarize all of the above with the help of the table below:
Name systematic units | characteristic peculiarities | Examples |
| lower plants | Absence of tissues and organs, aquatic habitat. The body is represented by a thallus and rhizoids | Ulva, ulotrix, fucus |
| Higher gymnosperms | The absence of flowers and fruits, the presence of resin passages in the wood, the leaves are needles | Spruce, pine, larch |
| higher angiosperms | Presence of flower and fruit | Apple tree, eggplant, rose |
| monocots | One cotyledon per seed embryo, fibrous root system, simple leaves, no cambium | Lily, garlic, rye |
| Dicotyledonous | Two cotyledons in the seed embryo, tap root system, presence of cambium | Ash, grapes, sea buckthorn |
The existing classification of plant organisms greatly facilitates the process of their study, and makes it possible to establish characteristic features and relationships between different groups.
