1 how many species of animals belong to the kingdom. Brief description and classification of the animal kingdom

There are an infinite number of different animal species on planet Earth. In order to understand them, it is worth studying the classification, which includes types, classes and orders. Species are the last step of division, and that is why their number is so great. It’s better to take several main ones, which are much smaller. It will be much more convenient to study the species included in them.

Sponges

For a long time, these animals were considered plants. Science has studied their structure quite recently. includes a wide variety of animal species. Examples of them can be listed for a very long time. Representatives always live in an aquatic environment, but outwardly they differ in a very impressive way. Sponges may look like featureless growths, cakes, twigs or lumps. The glass appearance of these animals looks incredibly beautiful and is a real masterpiece of nature - the so-called Venus basket or sea orange seem openwork and translucent.

They also have common features - for example, their lips hardly move. However, each species is able to obtain food without any problems - by passing impressive volumes of water through the body, microorganisms from which are the diet of these bizarre creatures. But the most interesting thing is that the coincidence of the name of these animals with the name of household utensils for washing or cleaning is not accidental: previously, living sponges were used for these purposes, which are good for the skin and can be very gentle to the touch.

Coelenterates

So, when listing the types of animals, examples should be divided into categories according to their main types. The next one is the coelenterates, low-organized creatures whose bodies consist of only two layers of cells. All of their species, with a few exceptions, live in aquatic environments. For example, this is the hydroid eudendrium, the coral acropora or the siphonophora physophora. Each of these species has a unique appearance - some look like small trees, while others resemble bird feathers. They are united by their habit of living in colonies and the structure of the body - as the name implies, the only body cavity is the intestine. All species can be divided into two groups: these are polyps, located in a certain place, or jellyfish, which can be mobile.

Worms

When listing animal species, the list of which is very long, it is worth mentioning this type. Worms can be flat, ringed or round. All these species are united by a structure of several layers of cells - ectoderm, endoderm and mesoderm. Worms have no body cavities; the body consists of parenchyma, which performs all the necessary functions. However, there is a difference between these types. have a brain stem, the round ones have only a few longitudinal and peripharyngeal nerve rings, and the annular ones have an abdominal nervous system. In addition, the latter have a closed circulatory system, which others do not have.

Shellfish

It is not only primitive animal species that are worth studying. The classification also includes much more developed organisms, for example, mollusks. This is the type that includes the maximum number of species. These are organisms that live in the sea (oysters, octopuses, mussels, squids), (toothless beetles, livebearers, pond snails) or in damp soil (snails, slugs). The sizes of mollusks of different species vary greatly; they can be very tiny (just a few millimeters) or reach more than twenty meters in length. Many are sedentary, but some can move in a reactive manner. These are squids and similar species of animals. The classification of mollusks also includes options such as cephalopods, bivalves and gastropods. Some have a shell consisting of several layers (horny and calcareous), but many have lost it during evolution. What unites all these animal species, the names of which, by the way, include snails and squids, is the structure of the digestive system. It consists of three sections with the foregut, middle and hindgut. Some individuals are distinguished by a muscular tongue with teeth, while others feed passively, simply filtering food from the water suspension with their gills. In all species, the circulatory system is not closed and includes blood vessels and a heart with several atria and a ventricle. Aquatic organisms breathe through gills, while terrestrial organisms breathe through lungs. is represented by the kidneys, and the nervous one - by scattered nodes with several large ganglia.

Arthropods

While listing the various species of animals, the list cannot be completed without mentioning these organisms. Arthropods include centipedes, scorpions, spiders, and crayfish. As a rule, these are bilaterally symmetrical animals with a body divided into segments. The body is covered with a chitin cuticle, which serves as an exoskeleton and protection for the body. Since this category includes a variety of animal species, examples of the respiratory system can be diametrically opposed - these are both lungs and gills. All representatives have different body shapes. As a rule, the body consists of several segments: head, chest and abdomen - all these types of animals have them. Examples, however, include some variations: in spiders the head and thorax are combined with the abdomen, while in ticks it is almost impossible to distinguish the segments at all.

Chordata

The most common and famous species of animals, photographs of which everyone has seen, belong to this type. It is the highest and presupposes the presence of a skeletal axis, a neural tube. The phylum includes three main types of organisms: tunicates, vertebrates, and tunicates. The first species of animals, examples of which are much less known than the second, most often live in an aquatic environment and settle in colonies. They have barrel- or pouch-shaped bodies, a ganglion-based nervous system, and underdeveloped sensory organs. Such organisms include the following species: ascidians, appendicularia, pyrosomes and others. These creatures reproduce in different ways, feeding on algae, small animals, and detritus.

Interestingly, the adult form is simplified, but the larvae are much more active and have developed sensory organs. Skullless do not have a separate head, which determines their name. They breathe with gills and do not have too many representatives; the most famous is the lancelet. Finally, vertebrates are the most famous and developed. This includes all species of mammals, fish, birds, amphibians and reptiles. This type developed back in prehistoric times. At the moment, about fifty thousand species of vertebrates are known to man.

The fauna, the classification of which meets the requirements of modern science, amazes with the variety of existing forms. And today scientists continue to discover new species of living creatures living on the planet. It is for this reason that zoology needs an order that takes into account the types of animals. It is the correct classification that allows science to develop and move forward.

Taxonomy

The science of taxonomy helps to navigate the diversity of species that represent the animal world of the Earth. Classifying animals into certain groups is one of the activities she does.

Newly discovered representatives of the animal world must be described by scientists and placed in the place of the general system where they should be located according to the criteria accepted in the scientific world.

The modern system of distributing the animal world into groups is based on determining the degree of their relationship, taking into account the origin, external and internal structure of organisms, and the ability to reproduce offspring. The types of animals are arranged in the table from lowest to highest. This corresponds to the general direction of the evolutionary development of the animal world on Earth.

Type - the basic concept of classification

When defining the concept of species, the body structure of animals, their habitat, and ability to reproduce are taken into account. Groups of individuals with common properties constitute animal species.

The classification of individual species, in turn, can be represented by populations. A feature of a group of animals that are part of a particular population is its relative isolation from representatives of the same species. The formation of such groups of animals is associated with their permanent habitat.

Carl Linnaeus and the classification of animals

There was not always a consensus among scientists about the rules for distributing representatives of living nature into certain groups. The current system was proposed by the famous scientist Carl Linnaeus more than three hundred years ago. It turned out to be very convenient and eliminated confusion in cases where scientists had to describe new species of animals.

The classification used today requires the inclusion of animal names only in Latin. The name contains two words. The first of them indicates the animal’s belonging to the genus and is a noun. The second word in the name must be an adjective and indicate the animal's species.
Such a classification of animals does not allow us to confuse, for example, a black-headed gull with some other species of bird. Among the huge variety of animals, only she has this name.

Genus and family

The group indicating the next systemic unit used when classifying animals is called genus. It brings together closely related species.

An example is the genus of crows, which includes representatives of such species as the jackdaw, crow, and rook. Close genera are grouped into families. For example, there is a widespread family called Corvidae. It included the following genera of birds: raven, jay, magpie, nutcracker.

Units and classes

The entire animal world, the basis of classification of which is species, is united into larger groups. These include squads. For example, the order Passeriformes includes several families: Tits, Swallows, Corvids.

Examples of orders include names such as Passerines, Owls, and Anseriformes. It is easy to guess that orders make up classes of animals. The classification proposed by Carl Linnaeus several centuries ago, refined and improved by modern scientists, rightfully has the status of universal.

Types of animals

All known classes of animals are combined into types. Modern science knows about twenty-five types of animals. An example is the phylum Chordates. It consists of the classes Birds, Mammals, Amphibians. All types known to science constitute the Animal Kingdom. The taxonomy is not arbitrary. All descriptions of animals and their assignment to one group or another in the classification system have a scientific basis. There are also international standards regulating the activities of scientists around the world.

It is necessary to know that the science of taxonomy continues to develop. Today, scientists agree on the identification of such categories as superorder, subtype, subclass in the general system. There is a discussion about what place Unicellular or Protozoa should occupy in the system. In some textbooks, these representatives are classified as a special group representing types of animals.

The classification distinguishes Multicellular organisms into another large group of animals. Among them, the following types are considered: Coelenterates, Flatworms, Roundworms, Annelids. There are other types of animals. For example, the phylum Molluscs is represented by the class Gastropods, Bivalves, Cephalopods. The phylum Arthropods combines the classes Crustaceans, Arachnids, and Insects.

Another numerous type of Chordata includes the classes Cartilaginous and Bony fish, which are united by scientists into the superclass Pisces. Amphibians, Reptiles, Birds and Mammals also belong to the phylum Chordata. In the most highly organized class of mammals, eleven orders are considered. The scheme for classifying animals proposed by zoologists is not only filled with specific content, but has a scientific basis.

From the simple jellyfish to the highly organized apes, the animal kingdom amazes us with a huge variety of living organisms. It is estimated that there are 9-10 million unique animal species on Earth. To make sense of such a bewildering number of organisms, biologists use a classification system that includes tiered ranks that group animals together based on their similarities. With a little practice, this system will seem very simple to you!

Steps

How to read a taxonomic table

Taxonomic categories of living organisms

Rank	Description	Examples
Kingdom	Largest taxonomic groups. Living organisms are divided into large and broad categories.	Animalia, Plantae, Bacteria
Type	Large taxonomic units that include members of a kingdom united by a certain similar structural or genetic common characteristic.	Chordata, Magnoliophyta, Proteobacteria
Class	An average taxonomic unit, including representatives of the same type, united by a narrower characteristic, for example, body structure, common ancestry, and so on.	Mammalia, Magnoliopsida, Gamma Proteobacteria
Squad	A group of organisms of the same class, united on the basis of body structure, certain external characteristics, or a common ancestor. The names of animal groups familiar to us often coincide with this taxonomic rank. For example, we call all representatives of the order Primates “monkeys.”	Primates, Rosales, Enterobacteriales
Family	A rather narrow group of organisms that unites externally similar organisms of related origin. The family name usually ends in "-y"	Hominidae, Rosaceae, Enterobacteriaceae
Genus	A special group of organisms that includes closely related members of the same family. Almost all members of the same genus are usually descendants of one common ancestor. The genus name forms the first part of the scientific name of the organism and is written in italics.	Homo , Rubus , Escherichia
View	The narrowest taxonomic unit. Species division is based on the identification of a narrow, specific group of organisms that usually have the same structure. Only individuals of the same species are able to interbreed and produce high-quality offspring. The species name forms the second part of the scientific name of the organism and is also written in italics.	sapiens , rosifolius , coli

Learn the taxonomic system of classifying animals. This system is based on the characteristics of the animals. It was proposed by the botanist Carl Lynaeus in the 18th century. However, when biologists talk about taxonomic ranks, they are talking about the classic seven categories shown in the table above. Categories are arranged in order of narrowing. Please note that the entries in the "Examples" column are color-coded, which allows you to follow the sequence in which you want to classify a living organism.

• Red entries correspond Homo sapiens, or to humans (animals).
• Highlighted in blue Rubus rosifolius, or Indian raspberry (plant).
• Information about Escherichia coli, which is better known as Escherichia coli (bacterium).

1. Remember the order of the taxonomic categories. You can use mnemonics to remember the seven main ranks: kingdom, phylum, class, order, family, genus, species. Come up with a phrase in which the first letter of the first word corresponds to the first letter in the word “kingdom,” the first letter of the second word corresponds to the first letter in the word “type,” and so on.

   Move from the broadest to the narrowest category. For example, any animal falls into the category of the animal kingdom, but not all can be called "sapiens". As you move down the list, you will notice that in order to fall into any narrow category, a living organism will have to have specific properties.

   Classify a living organism based on morphology. To classify an organism into any category, you need to determine its morphology. Morphology is the external and internal characteristics of an animal. For example, does it have fur or scales? What kind of stomach does he have? If you know the characteristics of an animal, you will be able to correctly identify its species.

Analysis of taxonomic categories

Start with the animal kingdom. All animals by definition belong to this group (also called metazoa). All organisms in this group are animals, and all organisms outside this group are non-animals. Thus, when starting classification, you can immediately find out whether an organism belongs to the animal kingdom or not.

• In addition to the animal kingdom, there is also the kingdom of plants, fungi, protists (single-celled eukaryotes) and shotworms (prokaryotes).
• Let's try to classify modern humans in accordance with the taxonomic system. Humans are animals that can breathe, so we can immediately determine the kingdom - this is the animal kingdom.

1. Determine the type. Type is a category that is immediately below kingdom. There are 35 phyla in the animal kingdom. To roughly generalize, organisms are grouped within a phylum based on their general morphology. For example, organisms classified as chordates have a rigid spine along the entire body with a spinal nerve above it and an alimentary canal below it. Representatives of echinoderms have a five-pointed shape and a spiny body surface.

   • Remember that taxonomic categories were developed before the advent of modern genetics, so organisms may not be grouped together correctly within a phylum. Some representatives of the phyla became the predecessors of other organisms. For example, flatworms are the predecessors of animals with a through digestive canal.
   • Returning to our example, people should be classified as chordates, because above our spine there is a canal with a spinal nerve.

2. Define a class. After type comes class. In total there are about 111 classes. Typically, living organisms are grouped into a class based on similar genetic and/or morphological characteristics. Below we give examples of classes within the phylum Chordata:

3. Determine the squad. After the class comes the squad. An order is a narrower group compared to a class or phylum, but broader than a species and genus. Here is an example of two orders within the class of reptiles:

   • Turtles.
   • Scaly (snakes, lizards).
   • The person belongs to primates, that is, to the same order that includes monkeys and human ancestors.

4. Define a family. After the detachment, the characteristics become increasingly narrower. The name of an animal familiar to us may come from the Latin name of its family. For example, geckos belong to the family Gekkonidae. Below we give several examples of families within the order Squamate:

   • Chamaeleonidae - chameleons
   • Iguanidae - iguanas
   • Scincidae (skinks) - skinks
   • The person belongs to the family hominids, like the great apes and human ancestors.

5. Determine the gender. The genus of an animal allows it to be separated from other animals that may be very similar to it or even have a similar name. For example, all animals in the gecko family (Gekkonidae) are geckos, but members of the genus Dixonius(leaf-shaped geckos) differ from members of the genus Lepidodactylus having scaly paws. There are a total of 51 genera within this family.

   • A person belongs to a family homo, which includes modern man and the ancient predecessors of man - Neanderthals, Cro-Magnons and so on.

6. Define the species. Species is the narrowest category in the taxonomic system. Members of the same species have a similar appearance, can interbreed within their species, and cannot do so with other species. In other words, only representatives of the same species can interbreed and produce offspring. When different species are crossed, offspring may be produced, but they will almost always be infertile and will not be able to reproduce (an example is the mule, which cannot produce offspring itself and is the result of crossing a horse and a donkey).

   • Remember that animals of the same kind can appear different, despite being related. For example, a Chihuahua and a Great Dane look different, but are members of the same species.
   • Man belongs to the species sapiens. The only representative of this species is man. Remember that modern people belonging to the genus homo and mind sapiens, have a number of morphological differences - size, face appearance, skin color, hair, and so on. However, all healthy couples consisting of a man and a woman can produce healthy offspring, so all representatives of these categories are people.

7. If necessary, define a subspecies. As a rule, species is the most accurate characteristic of a living organism. However, there are exceptions to this rule, and organisms are often classified into two or more subspecies. A species may have two or more subspecies, or none, but never just one. Often the need to use a subspecies arises when certain groups of living organisms can produce healthy offspring, but do not do so in natural conditions due to geographic separation, behavioral tendencies, or other reasons.

   • If we are talking about anatomically modern man (that is, about a person who lives now), we can use subtypes of the category sapiens, to separate man from man Idaltu - another representative of ancient man, part of the species Homo sapiens.

Animal taxonomy is a branch of taxonomy that studies the diversity of animal organisms and classifies them into groups. The foundations of animal taxonomy were laid in the work of C. Linnaeus “The System of Nature” (1735). The most general principles for classifying animals are the following.

To classify animals, the following are used: basic systematic categories: kingdom , type , Class , row , family , genus And view .

The smallest unit of classification is view - a set of individuals that have common hereditary characteristics of structure and vital functions, are capable of free interbreeding, produce fertile offspring and occupy a certain habitat area - habitat.

The largest unit of animal classification is kingdom .

The unification of taxa of lower order into systematic units of higher order is based not only on the similarity of structure and vital functions, but also on historical kinship, that is, descent from a common ancestor. A system of organisms based on common origin is called natural , and systems based only on the basis of similarity and without taking into account the degree of kinship - artificial .

In the taxonomy of individual groups of animals, auxiliary categories with prefixes are also used under - And above - (for example, subkingdom Unicellular, superclass Pisces).

Each animal species has its own scientific name, which consists of two words, that is, binary nomenclature. Binary nomenclature- a double name of a species, the first word of which indicates the generic affiliation, and the second - the species(for example, domestic dog, brown bear).

About 2 million animal species are now known, and this number is increasing as scientists describe thousands of new species every year. Animals can be divided into groups according to various characteristics. Based on food consumption, animals are divided into herbivores(deer, antelope, etc.), Carnivores(tigers, martens, wolves, etc.) And omnivores(brown bear). Based on the number of cells, animals are divided into unicellular, whose body consists of one cell (amoeba-proteus, ciliate-slipper, etc.); Colonial, whose body consists of a group of identical cells that combine with each other (Volvox, Eudorina, corals) multicellular, built from a large number of cells that have different structures and functions and can form organs and organ systems (coelenterates, worms, etc.). Multicellular animals, in turn, are divided into groups:

A) by the number of germ layers:

■ double-ball animals in which, during embryonic development, the body is formed from two germ layers: ectoderm And endoderm(sponges, coelenterates)

■ three-layer - animals whose body is formed from three germ layers: ectoderm, endoderm And mesoderm(other types)

b) behindbody symmetry:

■ promenevosymmetric - animals whose flesh can be drawn in several planes of symmetry (sponges, coelenterates)

■ binary symmetric, or bilateral - animals, the flesh of which can only be drawn in one plane, divides their body into two parts, mirror each other (the rest are multicellular) some binary-symmetrical animals, due to the peculiarities of their lifestyle, lose the bilateral symmetry of the body (gastropods, echinoderms) binary-symmetrical animals according to the method of mouth formation during embryonic development are divided into protostomes(flat and annelids, mollusks, arthropods) and deuterostomes(echinoderms, chordates).

V) Bytype of body cavity:

■ first-empty- animals in which the spaces between organs are lined with single-layer epithelium (roundworms)

■ secondary cavities, or coelomic - animals in which the spaces between organs are lined with their own epithelium (annelids, echinoderms, chordates)

■ zmishanoporozhninni - animals in which the secondary body cavity merges with the remains of the primary, forming a mixed cavity - mixocoel(arthropods).

The kingdom Animals includes more than 20 types, which are combined into two subkingdoms: Unicellular and multicellular.

Main groups of animals

So, the study of animal diversity is carried out by animal taxonomy, which uses certain systematic units and classifies animals, determining the place of species in the system of the animal world.

Education

There are an infinite number of different animal species on planet Earth. In order to understand them, it is worth studying the classification, which includes types, classes and orders. Species are the last step of division, and that is why their number is so great. It is better to take several basic types of animals, of which there are much fewer. It will be much more convenient to study the species included in them.

Sponges

For a long time, these animals were considered plants. Science has studied their structure quite recently. The sponge phylum includes a wide variety of animal species. Examples of them can be listed for a very long time. Representatives always live in an aquatic environment, but outwardly they differ in a very impressive way. Sponges may look like featureless growths, cakes, twigs or lumps. The glass appearance of these animals looks incredibly beautiful and is a real masterpiece of nature - the so-called Venus basket or sea orange seem openwork and translucent.
They also have common features - for example, their lips hardly move. However, each species is able to obtain food without any problems - by passing impressive volumes of water through the body, microorganisms from which are the diet of these bizarre creatures. But the most interesting thing is that the coincidence of the name of these animals with the name of household utensils for washing or cleaning is not accidental: previously, living sponges were used for these purposes, which are good for the skin and can be very gentle to the touch.

Coelenterates

So, when listing the types of animals, examples should be divided into categories according to their main types. The next one is the coelenterates, low-organized creatures whose bodies consist of only two layers of cells. All of their species, with a few exceptions, live in aquatic environments. For example, this is the hydroid eudendrium, the coral acropora or the siphonophora physophora. Each of these species has a unique appearance - some look like small trees, while others resemble bird feathers. They are united by their habit of living in colonies and the structure of the body - as the name implies, the only body cavity is the intestine. All species can be divided into two groups: these are polyps, located in a certain place, or jellyfish, which can be mobile.

Video on the topic

Worms

When listing animal species, the list of which is very long, it is worth mentioning this type. Worms can be flat, ringed or round. All these species are united by a structure of several layers of cells - ectoderm, endoderm and mesoderm. Worms have no body cavities; the body consists of parenchyma, which performs all the necessary functions. However, there is a difference between these types. Flatworms have a brain stem, roundworms have only a few longitudinal and peripharyngeal nerve rings, and annelids have an abdominal nervous system. In addition, the latter have a closed circulatory system, which others do not have.

Shellfish

It is not only primitive animal species that are worth studying. The classification also includes much more developed organisms, for example, mollusks. This is the type that includes the maximum number of species. These are organisms that live in the sea (oysters, octopuses, mussels, squid), fresh water (toothless, livebearers, pond snails) or in damp soil (snails, slugs). The sizes of mollusks of different species vary greatly; they can be very tiny (just a few millimeters) or reach more than twenty meters in length. Many are sedentary, but some can move in a reactive manner. These are squids and similar species of animals. The classification of mollusks also includes options such as cephalopods, bivalves and gastropods. Some have a shell consisting of several layers (horny and calcareous), but many have lost it during evolution. What unites all these animal species, the names of which, by the way, include snails and squids, is the structure of the digestive system. It consists of three sections with the foregut, middle and hindgut. Some individuals are distinguished by a muscular tongue with teeth, while others feed passively, simply filtering food from the water suspension with their gills. In all species, the circulatory system is not closed and includes blood vessels and a heart with several atria and a ventricle. Aquatic organisms breathe through gills, while terrestrial organisms breathe through lungs. The excretory system is represented by the kidneys, and the nervous system is represented by scattered nodes with several large ganglia.

Arthropods

While listing the various species of animals, the list cannot be completed without mentioning these organisms. Arthropods include centipedes, scorpions, spiders, and crayfish. As a rule, these are bilaterally symmetrical animals with a body divided into segments. The body is covered with a chitin cuticle, which serves as an exoskeleton and protection for the body. Since this category includes a variety of animal species, examples of the respiratory system can be diametrically opposed - these are both lungs and gills. All representatives have an open circulatory system. Body shape can be varied. As a rule, the body consists of several segments: head, chest and abdomen - all these types of animals have them. Examples, however, include some variations: in spiders the head and thorax are combined with the abdomen, while in ticks it is almost impossible to distinguish the segments at all.

Chordata

The most common and famous species of animals, photographs of which everyone has seen, belong to this type. It is the highest and presupposes the presence of a skeletal axis, a neural tube. The phylum includes three main types of organisms: tunicates, vertebrates, and tunicates. The first species of animals, examples of which are much less known than the second, most often live in an aquatic environment and settle in colonies. They have barrel- or pouch-shaped bodies, a ganglion-based nervous system, and underdeveloped sensory organs. Such organisms include the following species: ascidians, appendicularia, pyrosomes and others. These creatures reproduce in different ways, feeding on algae, small animals, and detritus. Interestingly, the adult form is simplified, but the larvae are much more active and have developed sensory organs. Skullless do not have a separate head, which determines their name. They breathe with gills and do not have too many representatives; the most famous is the lancelet. Finally, vertebrates are the most famous and developed group of animals. This includes all species of mammals, fish, birds, amphibians and reptiles. This type developed back in prehistoric times. At the moment, about fifty thousand species of vertebrates are known to man.

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Linnaeus admitted that within each species of animals and plants very wide differences in a number of characteristics are possible: in growth, fur color, etc. Therefore, for some species it is necessary to allow the existence of so-called “subspecies” or “varieties”.

However, Linnaeus argued that each species is sharply different from other species, even those close to it.

Section: Wild animals

He considered it completely impossible to allow a transition from one species of animal to another. According to Linnaeus, species are permanent, and they exist as long as God created them. According to Linnaeus’ definition, one species of animal or plant should include all those individuals that “resemble each other, like children resemble their parents, and are capable of reproducing by mating with each other.”

As we see, Linnaeus did not want to deviate in any way from the biblical theory of immutability and constancy of species, and therefore he sought to subordinate all his enormous knowledge as a scientist to the requirements of religion. But all his efforts invariably met with a number of difficult to resolve contradictions. Thus, his definition of species did not fit into the fact known to every rural owner that such undoubtedly different types of domestic animals as horses and donkeys are capable of interbreeding with each other and produce mules as offspring. Therefore, Linnaeus and his followers had to introduce an additional definition that offspring from individuals of the same species must necessarily be fertile. From different species, even if it is possible to obtain offspring, they will certainly be sterile (for example, a mule).

Soon, however, it turned out that this additional requirement of Linnaeus did not save the situation, for by now we know dozens of facts that indicate that in many cases, as a result of crossing obviously different, isolated, according to Linnaeus, species of animals and plants, They not only reproduce well, but also produce fertile offspring. Many similar cases are known for various species of wild ducks and geese; similar cases of the birth of fertile offspring can be observed when crossing different species of wild deer. Various types of wild sheep, etc., easily interbreed and produce fertile offspring.

Especially many examples of the fertility of offspring obtained from crossing parents descending from clearly different species are known in the plant world.

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Diversity of fauna

We are surrounded by a huge world of living beings - plants, animals, microorganisms - forming various combinations in different parts of our planet. Both the species themselves and their complexes - biocenoses - arose long before the appearance of humans as a biological species. With each era in the history of the Earth, this world changed more and more. The first primitive groups of organisms were replaced by new, morphophysiologically advanced groups that had broader evolutionary potential, and this continues as long as life exists on Earth. All this is the result of organic evolution, which can be called in one word - biodiversity.

Biodiversity includes hundreds of thousands of species, diversity within the populations of each species, and diversity of biocenoses, that is, diversity is observed at every level - from genes to ecosystems. This phenomenon has been of interest to humans for a long time. First, out of simple curiosity, and then quite consciously and often for practical purposes, a person studies his living environment. This process has no end, since with each century new problems arise and ways of understanding the composition and structure of the biosphere change. They are solved by the entire complex of biological sciences.

The study of the diversity of the organic world of our planet has become especially relevant after the role of diversity itself in maintaining the stability of the biosphere began to become clear. Its seemingly unshakable state and its inexhaustible resources turned out to be so disrupted over a short period of time that this began to cause justified concern for humanity. The growing pressure of human economic activity on the biosphere, the direct, although sometimes unconscious, destruction of many species of plants and animals, and changes in the habitat of other species can ultimately lead to catastrophic consequences.

Therefore, the increased interest in studying the role of biodiversity in the stability of the biosphere, from which humans receive resources for their existence, is understandable. Sustainable environmental management is the reasonable use of the gene pool of plants and animals in combination with its long-term conservation; this goal can be achieved only with a clear understanding of the processes occurring in the biosphere, the connections and interdependencies between the components of ecosystems, and, above all, from knowledge of the diversity that surrounds us.

All animals, like other living organisms, are united by scientists into systematic groups based on signs of kinship. The smallest of them is the species. All white hares living in the taiga, mixed forests or tundra belong to one species - the white hare.

Division of animals into groups: types, classes, orders, genera and species

In zoology, a species is a collection of animals that are similar to each other in all essential features of structure and vital activity, live in a certain territory and are capable of producing fertile offspring. Each animal that has unique structural and behavioral features is called an individual. Similar species are grouped into genera, genera into families, and families into orders. Larger systematic groups of animals - classes, types.

The study of the species richness of the animal world of our planet has a long history, but only in 1758 the famous scientist Carl Linnaeus listed all the animals known at that time, giving them their own Latin names. Over the more than two centuries that have passed since the publication of the tenth edition of Linnaean's System of Nature, our knowledge of the animal world of the Earth has increased immeasurably and continues to increase at a rapid pace. Although the process of studying the faunas of various parts of the globe is far from complete, the results of this study can already be presented.

In the literature one can also find forecast data on the number of animal species in the world. Thus, many believe that after the completion of work on studying the species composition of insects, there will be more than 1.5 million species. The same applies to roundworms and some other classes of animals. But even so, their species richness is literally stunning. As you might expect, the number of animal species in different parts of the globe varies. From the lowland areas of the tropical zone to the high latitudes and high altitudes of the mountain ranges, a decrease in diversity is clearly evident. This phenomenon is called the main diversity gradient. As a rule, this concerns not only the general diversity of the animal world, but also the number of species of specific taxa - orders, families, genera - in the faunas of the tropical and temperate zones of the Earth.

We are used to talking about the luxurious nature of the tropics and its poverty in the north. But it's not that simple. Many theories or hypotheses have been proposed to explain the phenomenon of biological diversity. If biological diversity is generally the result of evolution, then why did evolution occur at such different rates in the tropics and the Arctic Circle, on the plains and in the highlands, in the shallows and in the deep trenches of the oceans? Many attempts have been made to elucidate the causal relationships between biodiversity and environmental factors.

Factors influencing biodiversity

Depending on how environmental factors act on organisms - through the physical environment alone, through the physical and biotic environment, or through only the biotic environment, these factors or mechanisms are divided into primary, secondary and tertiary. Of course, the mechanisms themselves are not independent and act in concert and consistently. For some organisms, some factors are more important, for others - others. Let us briefly consider the hypotheses explaining biological diversity.

It has long been believed that the diversity of the animal world increases with the age of the communities in which species live. That is, the first in a series of reasons acting on diversity is called evolutionary time. In temperate zones, especially in the northern hemisphere, habitats are poor in species, since due to the Quaternary glaciation and other geological disturbances, animal species had too little time to adapt and fully develop their habitat. In the tropics, communities are highly diverse because they have not experienced external influences for a long time and evolution has proceeded unhindered, which has led to species richness. This hypothesis is also similar to another one, which takes into account the time required for the dispersal of species, but not for speciation, that is, a shorter ecological time. The following example gives us some idea of ​​this. If we are dealing with a recently emerged area such as a forest burnt area, then its species composition is poor because there simply was not enough time to colonize it with species from neighboring habitats. A classic example of this kind is the history of the settlement of animals on the island of Krakatoa after a catastrophic volcanic eruption that destroyed all life on the island in 1883. It took only 50 years for the formation of a new fauna, but this fauna turned out to be much poorer than the previous one, despite the fact that the island is located in the tropical zone and the distances to the nearest islands are very small.

The most common of all hypotheses is considered to be the one that connects species richness with climate stability, that is, with its slight fluctuations over the seasons. This is exactly what the climate of the tropics is like, especially the equatorial zone. An environment with a stable climate favors specialized species that occupy narrow ecological niches. Let us recall that an ecological niche is a reflection of the place occupied by an organism or species in a community, and this concept includes, in addition to resistance to physical environmental factors, also interactions with other organisms. This means that more species can fit into one area without competing for available resources. We add that in areas with a stable climate, the primary (plant) production of ecosystems is also stable and large, which ensures the coexistence of a larger number of species than in areas with unstable productivity.

The complexity of habitat structure is also important. For many groups of animals, in particular for birds, spatial heterogeneity plays a primary role. This can be seen from the fact that more species of birds live in the forest (multi-tiered structure) than in the meadow. Marine animals living in the intertidal zone, where the bottom consists of particles of various sizes, have more species of invertebrate animals than in the same shallow water with a uniform muddy bottom. Thus, there is a correlation between the structural complexity of the habitat and the species diversity of the fauna.

Species diversity can be determined by habitat productivity. In more productive habitats, food is more abundant and varied, so there is also more opportunity for consumer specialization than in less productive habitats. Many ecologists assign an important role in the formation of species-rich communities to such a biotic mechanism as competition. Charles Darwin pointed out the role of competition as a driving force in the process of speciation. Competition leads to divergence in ecological niches, and specialized species have narrow niches, allowing for high diversity. Particularly intense interspecific competition is observed in communities such as tropical rain forests. They are distinguished by the highest biological diversity and small sizes of species populations. It is known that 1 hectare of such forest can grow from 50 to 100 species of trees. High plant diversity, in turn, favors the development of animal diversity, especially birds and insects, while many species are rare and the number of individuals of any one species is small.

Finally, biodiversity researchers attribute an important place among its mechanisms to predation. This mechanism is that predators feed on prey that is most abundant in a given area, that is, the most common, so-called background species. In this case, predators act as a rarefaction factor. Therefore, they make local coexistence of species possible, weakening competition between them and leading to an increase in various prey.

In all likelihood, none of the environmental factors, taken separately, is able to explain the reason for the diversity of species in a particular landscape zone of the globe. Recently, a special discussion of the correlation between climate and diversity was devoted to work based on a comparison of the number of species of certain groups of insects on the territory of the Russian Plain. The authors came to the conclusion that the problem of the relationship between climate and biodiversity is still at the descriptive stage of study. In addition, they believe that the evidence base to link the response of biota to global warming is still insufficient. The last statement is important in the sense that it calls into question the statements of many ecologists who talk about the global consequences of global warming caused by human activity.

The studies on the basis of which certain hypotheses were proposed were carried out on various groups of animals with different requirements for the environment. As a result, the conclusions of the authors often do not coincide. Different groups of organisms have different correlations of diversity with vegetation structure, environmental stability, moisture conditions, etc. Therefore, diversity is the result of contradictions, a compromise between the genetically inherent potential of morphogenesis and environmental resources. In a general sense, we can say that evolution is directed towards increasing diversity. The evolution of diversity is a self-propelling process; it creates the prerequisites for the further evolution of diversity, therefore it can be argued that diversity generates diversity according to the feedback principle.

How many species of animals inhabit the Earth?

One million, ten million, fifty? We don't know. Over a million living creatures have been scientifically described, named and cataloged. This includes almost all large, visible and accessible representatives of the fauna - birds, mammals and reptiles.

Judging by the number of “new” insects discovered annually, we know only a small part of their total number. In some collections collected under the canopy of tropical jungles, about 90% of insect species were previously unknown to science. Therefore, according to estimates by a number of scientists, there can be up to 50 million species of insects alone, plus a countless army of mollusks, worms, crustaceans and similar small living creatures.

Compared to this wealth, 40 thousand species of vertebrates - fish, amphibians, reptiles, birds and mammals, including you and me - constitute a more than modest part of the animal world. This is clearly seen in the systematization of animals into groups with similar characteristics, each of which is called a phylum. There are 32 types of animals in total, and vertebrates make up only a small part of one of them. All other types cover a bewildering variety of living creatures, from plant-like sponges to intelligent octopuses. We know many of them by name at best.

Using new collection methods or exploring previously neglected sites can also produce a sudden surge in the number of new species. In recent decades, such a “gold mine” has turned out to be the interstitial fauna of sea coasts (animals living among grains of sand in the intertidal zone). Not long ago, completely unexpected discoveries were accidentally made, which turned out to be, at least for zoologists, sensational. We are, of course, not talking about Bigfoot or sea monsters. In 1938, a coelacanth was caught - the first living representative of the lobe-finned fish, from which amphibians originated, which were considered extinct about 70 million years ago. Extinct even earlier; in the Devonian, they also considered the class of mollusks Monoplacophora, interesting because imprints of places to which muscles were attached were found on their shells. This indicates an elementary segmentation of their body and, according to some scientists, indicates a connection between the mollusks and annelids. And since 1952, we have known these animals not only in the form of fossils. They still live today! Representatives of the genera Neopilina and Vema were found in the Pacific Ocean at a depth of several thousand meters. True, the supposed relationship with annelids has not yet been confirmed.

Somewhat later, another sensation: for the first time, gastropods with a bivalve shell were found. It was tempting to see them as a link between gastropods and bivalves. But this assumption was not confirmed either. Meanwhile, two more species of these unusual snails were discovered. They were found not in the inaccessible depths of the sea, but in shallow waters - off the coast of Japan and Australia, in the Gulf of California and off the island of Jamaica. As you can see, the history of zoological discoveries on Earth is not over. Mammal researchers can also hope for luck - just recently, in 1938, a new species of whale, the Tasmanian beaked whale, was described. Then the sea unexpectedly washed several animals ashore. Yet in small and already well-studied groups, such discoveries are very rare.

In the classes of birds and mammals, the number of species even decreased. This happened not so much due to extinction, but due to the fact that over time, scientists abandoned too fractional divisions and many species were united. Thus, the total number of known and as yet unknown species of animals is, apparently, two, or even three million. Incredible variety! But this is only a small fraction of the species that arose and disappeared in the process of evolution. Some once-dominant groups of animals, once so numerous that scientists use their fossil remains to determine the age of geological strata, have become completely extinct. Of others, which also reached significant prosperity in the past, for example, brachiopods, only pitiful crumbs have survived. But even in such ancient classes as crustaceans, insects, fish, and even in the relatively young classes of birds and mammals, the number of extinct species is much greater than the number of our “contemporaries.”

The distribution of animals on land, in fresh water bodies and seas is extremely uneven. The sea is the cradle of life; the earliest stages of the evolution of the animal world took place here. Many ancient groups never found their way to land or fresh water. This applies to the cephalopods, echinoderms and tunicates that thrive in the seas to this day, as well as to some small surviving groups and to many extinct branches of the animal kingdom. But, despite the vast expanses of the World Ocean, it would be a gross mistake to conclude that the number of marine species exceeds the number of freshwater or terrestrial ones.

The millions of years that have passed since their appearance, and the relative constancy of environmental conditions, would seem to have allowed marine animals to exist much longer and opened up limitless scope for development. But no! It is precisely due to these circumstances that the number of species in the sea is relatively small: the constancy of conditions over a large area and for a long time contributes to the preservation, rather than fragmentation, of any group of animals. The huge number of species of terrestrial animals is the result of the most diverse conditions of their existence. It is surprising and little understood why the return route to the sea turned out to be inaccessible for insects that have adapted to the most incredible conditions on land. On any coast, except perhaps the coldest, we will find many species of insects, but there are none in the thickness of sea water. True, in the open sea you can find Halobatidae bugs, reminiscent of water striders from our puddles and ponds. They also rush along the surface of the water, but that’s all. Spiders also did not become true sea inhabitants, although some of them settled in coral reefs.

Of course, there are species that differ little in their environmental requirements. However, as a rule, such differences are still expressed quite clearly. The very fact of the existence of many specialized species indicates that animals were able to adapt to almost any food and any climatic conditions within the boundaries determined by the biochemical laws of the body. As a result of this process, which lasted hundreds of millions of years, animals populated the globe from pole to pole. They withstand the snow storms of the long polar night, live in subpolar reservoirs and deep seas at temperatures around 0°C. Life does not stop in hot springs, where the water temperature reaches and sometimes exceeds 50°C. However, in most animals, already at temperatures slightly below 50 ° C, enzymatic systems become disordered and proteins change irreversibly. It seems to us unbearable the heat that the animals of the steppes and deserts, located directly on the surface of the soil, withstand, because it heats up much more than the air. True, many desert inhabitants leave their underground shelters only at night or in the evening.

The animal world is large and diverse. Animals are animals, but adults decided to divide them all into groups according to certain characteristics. The science of classifying animals is called systematics or taxonomy. This science determines family relationships between organisms. The degree of relationship is not always determined by external similarity. For example, marsupial mice are very similar to ordinary mice, and tupayas are very similar to squirrels. However, these animals belong to different orders. But armadillos, anteaters and sloths, completely different from each other, are united into one squad. The fact is that family ties between animals are determined by their origin. By studying the skeletal structure and dental system of animals, scientists determine which animals are closest to each other, and paleontological finds of ancient extinct species of animals help to more accurately establish family ties between their descendants.

Types of multicellular animals: sponges, bryozoans, flatworms, roundworms and annelids (worms), coelenterates, arthropods, molluscs, echinoderms and chordates. Chordates are the most progressive type of animals.

Kingdom Animals and their classification (Scheme, Table)

They are united by the presence of a chord - the primary skeletal axis. The most highly developed chordates are grouped into the vertebrate subphylum. Their notochord is transformed into a spine. The rest are called invertebrates.

Types are divided into classes. There are 5 classes of vertebrates in total: fish, amphibians, birds, reptiles (reptiles) and mammals (animals). Mammals are the most highly organized animals of all vertebrates.

Classes can be divided into subclasses. For example, mammals are divided into subclasses: viviparous and oviparous. Subclasses are divided into infraclasses, and then into squads. Each squad is divided into families, families - on childbirth, childbirth - on kinds. Species is the specific name of an animal, for example, a white hare.

The classifications are approximate and change all the time. For example, now lagomorphs have been moved from rodents into an independent order.

In fact, those groups of animals that are studied in elementary school are types and classes of animals, given intermixed.

The first mammals appeared on Earth about 200 million years ago, separating from animal-like reptiles.

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Diversity of the animal world

The living nature that surrounds us in all its diversity is the result of the long historical development of the organic world on Earth, which began almost 3.5 billion years ago. The biological diversity of living organisms on our planet is great. Each type is unique and inimitable. For example, there are more than 1.5 million species of animals. However, according to some scientists, there are at least 2 million species in the insect class alone, the vast majority of which are concentrated in the tropical zone. The number of animals in this class is also large - it is expressed in numbers with 12 zeros. And there can be up to 77 million different single-celled planktonic organisms in just 1 m3 of water.

Tropical rainforests are particularly rich in biological diversity. The development of human civilization is accompanied by an increase in anthropogenic pressure on natural communities of organisms, in particular the destruction of the largest tracts of Amazon forests, which leads to the disappearance of a number of animal and plant species and a decrease in biodiversity.

A special science - taxonomy - helps to understand all the diversity of the organic world. Just as a good collector classifies the objects he collects according to a certain system, a taxonomist classifies living organisms based on characteristics. Every year, scientists discover, describe and classify new species of plants, animals, bacteria, etc. Therefore, taxonomy as a science is constantly developing. Thus, in 1914, a representative of a then unknown invertebrate animal was described for the first time, and only in 1955 did the domestic zoologist A.V. Ivanov (1906-1993) substantiate and prove that it belongs to a completely new type of invertebrate - pogonophora.

Development of taxonomy (creation of artificial classification systems). Attempts to classify organisms were made by scientists back in ancient times. The outstanding ancient Greek scientist Aristotle described over 500 species of animals and created the first classification of animals, dividing all then known animals into the following groups 1: [ Animals without blood: soft-bodied (corresponds to cephalopods); soft-shelled (crustaceans); insects; cranioderms (shell molluscs and echinoderms).

II. Animals with blood: viviparous quadrupeds (corresponding to mammals); birds; oviparous quadrupeds and legless (amphibians and reptiles); viviparous legless animals with pulmonary respiration (cetaceans); Legless, scaly fish that breathe through gills.

By the end of the 17th century. a huge amount of material was accumulated on the diversity of forms of animals and plants, which required the introduction of the concept of species; this was first done in the works of the English scientist John Ray (1627-1705). He defined a species as a group of morphologically similar individuals and attempted to classify plants based on the structure of their vegetative organs. However, the founder of modern taxonomy is rightfully considered the famous Swedish scientist Carl Linnaeus (1707-1778), who in 1735 published his famous work “The System of Nature”. K. Linnaeus took the structure of a flower as the basis for classifying plants. He grouped closely related species into genera, similar genera into orders, and orders into classes. Thus, he developed and proposed a hierarchy of systematic categories. In total, scientists have identified 24 classes of plants. To designate the species, K. Linnaeus introduced double, or binary, Latin nomenclature. The first word means the name of the genus, the second - the species, for example Sturnus vulgaris. In different languages, the name of this species is written differently: in Russian - common starling, in English - common starling, in German - Gemeiner Star, in French - etourneau sansonnet, etc. Common Latin names of species make it possible to understand who we are talking about and facilitate communication between scientists from different countries. In the animal system, K. Linnaeus identified 6 classes: Mammalia (Mammals). He placed man and monkeys in the same order, Primates; Aves (Birds); Amphibia (Reptiles, or Amphibians and Reptiles); Pisces (Pisces); Insecta (Insects); Vermes (Worms).

The emergence of a natural classification system. K. Linnaeus' system, despite all its undeniable advantages, was inherently artificial. It was built on the basis of external similarities between different species of plants and animals, and not on the basis of their true relationship. As a result, completely unrelated species ended up in the same systematic groups, and closely related species found themselves separated from each other. For example, Linnaeus considered the number of stamens in plant flowers as an important systematic feature. As a result of this approach, artificial groups of plants were created. Thus, viburnum and carrots, bells and currants fell into one group only because the flowers of these plants have 5 stamens. Linnaeus placed plants different in the nature of pollination into one class of monoecious plants: spruce, birch, duckweed, nettle, etc. However, despite the shortcomings and errors in the classification system, the works of C. Linnaeus played a huge role in the development of science, allowing scientists to navigate the diversity of living organisms.

The modern classification system can be presented in the form of the following scheme: empire, superkingdom, kingdom, subkingdom, type (division - for plants), subtype, class, order (order - for plants), family, genus, species. For extensive systematic groups, additional intermediate systematic categories have also been introduced, such as superclass, subclass, superorder, suborder, superfamily, subfamily. For example, the classes of cartilaginous and bony fishes are combined into a superclass of fishes. In the class of bony fishes, subclasses of ray-finned and lobe-finned fish, etc. are distinguished.

Previously, all living organisms were divided into two kingdoms - Animals and Plants. Over time, organisms were discovered that could not be classified as one of them. Currently, all organisms known to science are divided into two empires: Precellular (viruses and phages) and Cellular (all other organisms).

Precellular life forms. In the Pre-Cellular Empire there is only one kingdom - viruses. They are non-cellular life forms that can invade and reproduce in living cells.

Classification

Science first learned about viruses in 1892, when Russian microbiologist D.I. Ivanovsky (1864-1920) discovered and described the tobacco mosaic virus, the causative agent of tobacco mosaic disease. Since that time, a special branch of microbiology has emerged - virology. There are DNA-containing and RNA-containing viruses.

Cellular life forms. The Cellular Empire is divided into two superkingdoms (Pre-nuclear, or Prokaryotes, and Nuclear, or Eukaryotes). Prokaryotes are organisms whose cells do not have a formed (membrane-bound) nucleus. The prokaryotes include the kingdom of Drobyanok, which includes half the kingdom of Bacteria and Blue-greens (Cyanobacteria). Eukaryotes are organisms whose cells have a formed nucleus. These include the kingdoms of Animals, Fungi and Plants.

In general, the Cellular Empire consists of four kingdoms: Grinders, Mushrooms, Plants and Animals.

Control questions

1. What is the essence of the idea of ​​the spontaneous generation of life?

2. How did L. Pasteur prove the inconsistency of the theory of spontaneous generation of organisms?

3. Describe the main idea of ​​A.I. Oparin’s theory of chemical evolution.

4. Give a brief description of the main stages of the origin of life on Earth according to the theory of J. Bernal.

5. Which class of modern animals is represented by the largest number of species?

6. What are the main tasks of taxonomy?

7. Why is Carl Linnaeus considered the founder of modern taxonomy?

8. What is the main merit of Charles Darwin in systematics?

9. What is the main difference between prokaryotes and eukaryotes?

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Variety of animal species

Animals are the most diverse group of organisms on Earth. Currently, there are about 2 million species of animals on the planet. Most of them are insects (butterflies, mosquitoes, beetles, flies...). About 130 thousand species of mollusks are known: snails, slugs, pearl barley, squid. The diversity of fish is much more modest - only 25 thousand species, and of birds - 8,600 species. And there are only about 4 thousand species of mammals.

Note that we are not talking about the total number of animals in general, but about the number of animal species. The absolute number of animals on our planet is expressed by an astronomical number!

Animals vary in size. For example, a giant blue whale's body weight reaches 150 tons (the mass of such a whale's tongue is equal to the mass of a small elephant), and the slipper ciliates can only be detected using a microscope.

Animals in any habitat do not live everywhere, but occupy the most favorable areas for them. They are called habitats (or habitats) of animals. For example, nightingales are found in damp and shaded areas of the forest. Pike in rivers prefer places with slow currents (pools, pools), overgrown near the banks.

Organisms in nature do not live in isolation from each other, but in species.

A species is a collection of similar individuals capable of interbreeding to form fertile offspring. A species consists of many individuals that reproduce, disperse, and maintain unity in the struggle for existence. The distribution area of ​​a species is called its range.

Zoology is the science of animals. People have been using animals in their lives for a long time. By hunting for animals, protecting their homes from predators and poisonous snakes, etc., they acquired knowledge about their appearance, habitat, lifestyle, habits and passed it on from generation to generation. Over time, books about animals appeared, and the science of zoology arose (from the Greek “zo-on” - animal and “logos” - word, doctrine). Her birth dates back to the 3rd century. BC. and is associated with the name of the ancient Greek scientist Aristotle.

Modern zoology is a whole system of animal sciences. Some of them study the structure, development of animals, lifestyle, distribution on Earth; others are specific groups of animals, for example only fish (ichthyology) or only insects (entomology). The knowledge gained by zoological sciences is of great importance for the protection and restoration of the numbers of a number of animals, the fight against plant pests, carriers and pathogens of human and animal diseases, etc.
Classification of animals. All animals, like other living organisms, are united by scientists into systematic groups based on signs of kinship. The smallest of them is the species. All white hares living in the taiga, mixed forests or tundra belong to one species - the white hare. In zoology, a species is a collection of animals that are similar to each other in all essential features of structure and vital activity, live in a certain territory and are capable of producing fertile offspring. Each animal that has unique structural and behavioral features is called an individual. Similar species are grouped into genera, genera into families, and families into orders. Larger systematic groups of animals - classes, types.
The animal kingdom includes two subkingdoms: Unicellular animals and Multicellular animals, which unite more than 20 types and several hundred classes.

The species diversity of a biocenosis is the totality of plant and animal species that form a given biocenosis; represented by all groups of organisms - producers, consumers and decomposers; disruption of any link in the food chain causes disruption of the biocenosis as a whole (for example, deforestation leads to a change in the species composition of insects, birds, and, consequently, animals).

6 main groups of animals, their brief characteristics and photos

Species diversity is the number of species in a given community or area. There are alpha diversity (the number of species in the biotope in question), beta diversity (the number of species in all biotopes in a given area) and gamma diversity.

Any ecosystem is composed of a certain number of species of plants and animals, between which a kind of balance has been established. Each population of individual species is characterized by a certain relationship between the formation of new individuals and the death of old ones. The system as a whole is characterized by the periodic appearance of some species (as a result of divergence or introduction) and the eradication of others.

The equilibrium number of species decreases when the number of new species decreases and when they become extinct. Let's take an example of an island ecosystem. The formation of species in the island system is replaced by the appearance of species from the nearby mainland; if there are few species on the island, then the rate of colonization of the island by new species will decrease, and the emergence of new species will slow down sharply. If all the species characteristic of the mainland are present on the island, there will be no possibility of species appearing from the mainland at all. As species on the island increase, the rate of extinction increases, due to the large number of populations present and the fact that increased competition accelerates the exclusion of any species.

Small populations tend to die out faster than large populations. On large islands the number of species is higher than on small islands and the extinction curve of species on small islands is higher than on large islands. Mainland populations of most species tend to be larger than island populations, and therefore the rate of species extinction on the island is higher than on the mainland. On the mainland, new species appear more often, formed within a certain region and due to the divergence of species in this region, and less due to the arrival of new species from other territories.

The number of species in a region influences the rate of speciation. If the number of species is high, then stabilization is noted in this process due to a decrease in the ecological capabilities of the system for the formation of new species. The role of species loss is similar in marine island systems and continental systems. The equilibrium number of species indicates the same number of outgoing and emerging species. The intensity of species renewal in most cases exceeds the change in their diversity. The longer the period of ecosystem development, the higher the proportion of endemics in it. In addition, limited lake space and limited diversity of conditions constrain divergence processes. That is, in lake systems the number of species relatively quickly approaches a stable level. Taxa that achieve great diversity are quickly replaced by taxa that evolve slowly but have greater ecological potential and, naturally, are more competitive.