The division of the history of the earth into eras and periods. Human evolution. Initial stages of development

Structure

Examples of structures of icosahedral virions.
A. A virus that does not have a lipid envelope (for example, picornavirus).
B. Enveloped virus (eg herpesvirus).
Numbers indicate: (1) capsid, (2) genomic nucleic acid, (3) capsomere, (4) nucleocapsid, (5) virion, (6) lipid envelope, (7) membrane envelope proteins.

Classification

Baltimore classification

Nobel laureate biologist David Baltimore proposed his classification scheme for viruses based on differences in the mechanism of mRNA production. This system includes seven main groups:

• (I) Viruses containing double-stranded DNA and lacking an RNA stage (e.g. herpesviruses, poxviruses, papovaviruses, mimiviruses).

• (II) Viruses containing double-stranded RNA (eg rotaviruses).

• (III) Viruses containing a single-stranded DNA molecule (for example, parvoviruses).

• (IV) Viruses containing a positive polarity single-stranded RNA molecule (eg picornaviruses, flaviviruses).

• (V) Viruses containing a single-stranded RNA molecule of negative or dual polarity (eg, orthomyxoviruses, filoviruses).

• (VI) Viruses containing a single-stranded RNA molecule and having in their life cycle the stage of DNA synthesis on an RNA template, retroviruses (for example, HIV).

• (VII) Viruses containing double-stranded DNA and having a stage of DNA synthesis on an RNA template in their life cycle, retroid viruses (for example, hepatitis B virus).

Currently, for the classification of viruses, both systems are used simultaneously, as complementary to each other.

Further division is made on the basis of such features as the structure of the genome (the presence of segments, a circular or linear molecule), genetic similarity with other viruses, the presence of a lipid membrane, the taxonomic affiliation of the host organism, and so on.

Story

Application of viruses

Links

• "The Nobel Committee was hit by viruses" Article. Newspaper "Kommersant" No. 181 (3998) dated 07.10.2008.

Literature

• Mayo M.A., Pringle C.R. Virus taxonomy - 1997 // Journal of General Virology. - 1998. - No. 79. - S. 649-657.

Viruses were discovered by D.I. Ivanovsky (1892, tobacco mosaic virus).

If viruses are isolated in their pure form, then they exist in the form of crystals (they do not have their own metabolism, reproduction and other properties of the living). Because of this, many scientists consider viruses to be an intermediate stage between living and non-living objects.

Viruses are non-cellular life forms. Virus particles (virions) are not cells:

• viruses are much smaller than cells;
• viruses are much simpler than cells by structure - they consist only of a nucleic acid and a protein shell, consisting of many identical protein molecules.
• Viruses contain either DNA or RNA.

Synthesis of virus components:

• The nucleic acid of a virus contains information about viral proteins. The cell makes these proteins itself, on its own ribosomes.
• The nucleic acid of the virus is reproduced by the cell itself, with the help of its enzymes.
• Then the virus particles self-assemble.

Meaning of viruses:

• cause infectious diseases (flu, herpes, AIDS, etc.)
• some viruses can insert their DNA into the host cell's chromosomes, causing mutations.

AIDS

The AIDS virus is very unstable, easily destroyed in the air. You can get infected with it only through sexual contact without a condom and through a transfusion of infected blood.

Answer

Establish a correspondence between the features of a biological object and the object to which this feature belongs: 1) bacteriophage, 2) Escherichia coli. Write the numbers 1 and 2 in the correct order.
A) consists of a nucleic acid and a capsid
B) murein cell wall
C) outside the body is in the form of crystals
D) can be in symbiosis with a person
D) has ribosomes
E) has a tail channel

Answer

Choose one, the most correct option. Precellular life forms are studied by science
1) virology
2) mycology
3) bacteriology
4) histology

Answer

Choose one, the most correct option. AIDS virus infects human blood
1) erythrocytes
2) platelets
3) lymphocytes
4) platelets

Answer

Answer

Choose one, the most correct option. Cells of what organisms are affected by bacteriophage?
1) lichens
2) mushrooms
3) prokaryotes
4) protozoa

Answer

Choose one, the most correct option. The immunodeficiency virus primarily affects
1) erythrocytes
2) platelets
3) phagocytes
4) lymphocytes

Answer

Choose one, the most correct option. In what environment does the AIDS virus usually die?
1) in the lymph
2) in breast milk
3) in saliva
4) in the air

Answer

Choose one, the most correct option. Viruses have the characteristics of a living being, such as
1) food
2) growth
3) metabolism
4) heredity

Answer

Answer

1. Install correct sequence stages of reproduction of DNA-containing viruses. Write down the corresponding sequence of numbers in the table.
1) the release of the virus in environment
2) protein synthesis of the virus in the cell
3) introduction of DNA into the cell
4) synthesis of virus DNA in a cell
5) attachment of the virus to the cell

Answer

2. Set the sequence of steps life cycle bacteriophage. Write down the corresponding sequence of numbers.
1) biosynthesis of DNA and proteins of a bacteriophage by a bacterial cell
2) rupture of the bacterial shell, release of bacteriophages and infection of new bacterial cells
3) penetration of the bacteriophage DNA into the cell and embedding it into the circular DNA of the bacterium
4) bacteriophage attachment to the bacterial cell membrane
5) assembly of new bacteriophages

Answer

Answer

1) have an unformed core
2) reproduce only in other cells
3) do not have membrane organelles
4) carry out chemosynthesis
5) able to crystallize
6) are formed by a protein coat and nucleic acid

Answer

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Viruses as opposed to bacteria
1) have a cellular structure
2) have an unformed core
3) are formed by a protein coat and nucleic acid
4) belong to free-living forms
5) multiply only in other cells
6) are a non-cellular form of life

Answer

1. Establish a correspondence between the trait of an organism and the group for which it is characteristic: 1) prokaryotes, 2) viruses.
A) the cellular structure of the body
B) the presence of its own metabolism
C) insertion of one's own DNA into the DNA of the host cell
D) consists of a nucleic acid and a protein coat
D) reproduction by division in two
E) the ability to reverse transcription

Answer

Answer

Answer

Answer

Answer

Answer

Choose two correct answers from five and write down the numbers under which they are indicated. Metabolism as a property of living things is characteristic of
1) plant viruses
2) protozoa
3) soil bacteria
4) animal viruses
5) bacteriophages

Answer

© D.V. Pozdnyakov, 2009-2019

Sizes - from 15 to 2000 nm (some plant viruses). The largest among animal and human viruses is the causative agent of smallpox - up to 450 nm.

Simple viruses have an envelope capsid, which consists only of protein subunits ( capsomeres). The capsomeres of most viruses have helical or cubic symmetry. Virions with helical symmetry are rod-shaped. Most viruses are built according to the spiral type of symmetry, affecting plants. Most of the viruses that infect human and animal cells have a cubic symmetry type.

Complex viruses

Complex viruses can be additionally coated with a lipoprotein surface membrane with glycoproteins that are part of the plasma membrane of the host cell (for example, pox viruses, hepatitis B), that is, they have supercapsid. With the help of glycoproteins, specific receptors on the surface of the host cell membrane are recognized and the viral particle is attached to it. Carbohydrate sections of glycoproteins protrude above the surface of the virus in the form of pointed sticks. The additional envelope can fuse with the plasma membrane of the host cell and facilitate the penetration of the contents of the viral particle deep into the cell. Additional shells may include enzymes that provide the synthesis of viral nucleic acids in the host cell and some other reactions.

Bacteriophages have a rather complex structure. They are classified as complex viruses. For example, bacteriophage T4 consists of an extended part - the head, process and tail filaments. The head consists of a capsid that contains nucleic acid. The process includes a collar, a hollow shaft surrounded by a contracting sheath and resembling a stretched spring, and a basal plate with caudal spines and filaments.

Virus classification

The classification of viruses is based on the symmetry of viruses, the presence or absence of an outer shell.

Viruses only survive in the cells of living organisms. Their nucleic acid is able to induce the synthesis of viral particles of the host cell. Outside the cell, viruses do not show signs of life and are called virions.

The life cycle of a virus consists of two phases: extracellular(virion), in which it does not show signs of vital activity, and intracellular. Virus particles outside the host organism do not lose their ability to infect for some time. For example, the polio virus can remain infectious for several days, smallpox for months. The hepatitis B virus retains it even with short-term boiling.

The active processes of some viruses take place in the nucleus, others in the cytoplasm, and in some, both in the nucleus and in the cytoplasm.

Types of interaction between cells and viruses

There are several types of interaction between cells and viruses:

1. Productive - the nucleic acid of the virus induces the synthesis of its own substances in the host cell with the formation of a new generation.
2. abortive - reproduction is interrupted at some stage, and a new generation is not formed.
3. Virogenic - the nucleic acid of the virus is integrated into the genome of the host cell and is not capable of reproduction.

3.5 billion years ago - the formation of "primary organic broth", then - "coacervate drops" from the molecules of proteins, fats and carbohydrates.

Coacervates, connecting with nucleic acids, formed probionts - protocells capable of self-reproduction. These are prokaryotes - the first non-nuclear living organisms (bacteria and blue-green algae).

2. Proterozoic era - 2600-570 million years ago.

1.9 billion years ago, the first autotrophs appeared, the process of photosynthesis began, the atmosphere began to be saturated with oxygen and the formation of an ozone screen. 1.1 billion years ago, the first multicellular invertebrate organisms appeared.

3. Paleozoic era -570-235 million years ago.

3.1 Cambrian (570-490 million years ago). P transition from slow to fast evolution (the beginning of an evolutionary explosion).

3.2 Ordovician (490-435 million years ago). Trilobites and mollusks appear. 450 million years ago, the first vertebrates appeared - fish and fish-like.

3.3.Silur (435-400 million years ago). The end of the establishment of the ozone screen. The first exit of plants and animals to land.

3.4 Devonian (400-345 million years ago). The appearance of cartilaginous fish (400 million years ago).

3.5. Carboniferous (345-280 million years ago). The appearance of amphibians (330 million years ago) and reptiles (300 million years ago).

3.6. Perm (280-235 million years ago. Change of flora and fauna.

4. Mesozoic era (235-66 million years ago).

4.1. Triassic (235-185 million years ago). Appearance of the first dinosaurs. The appearance of the first mammals (200 million years ago). The emergence and development of coniferous vegetation, in reservoirs - turtles, crocodiles, ichthyosaurs.

4.2. Jurassic period(185-135 million years ago). Dinosaurs dominate on land. The emergence and development of birds (160 million years ago).

4.3 Cretaceous period (135-66 million years ago). Cooling of the climate and intensification of radioactive radiation. The extinction of the previously dominant dinosaurs, pterosaurs, ammonites, belennites, etc. Mammals and bony fish are rapidly developing in the fauna, flowering plants in the flora.

5. Cenozoic era (66 million years ago - present).

5.1. Paleogene (Lower Tertiary period) - 66-25 million years ago. The rise of new mountain ranges in place of the drying Tethys Ocean. Formation of modern fauna and flora. A wide distribution in the fauna of warm-blooded animals of mammals and birds, the most adapted to a changing environment.

AT aquatic environment- development bony fish. Flora on land is dominated by angiosperms.

5.2. Neogene (Upper Tertiary period) - 25-1 million years ago. The sinking of the ocean floor, the climate becomes colder, drier and more continental.

5.3 Anthropogenic (Quaternary), modern period -1 million years ago - present.

Oceans and continents take on a modern look. Ice ages alternate with periods of climate warming. A man appears - Homo sapiens. 10-12 thousand years ago after the last ice age flora and fauna of the Earth acquires a modern look.

As we already know, the first invertebrates, according to modern concepts, occurred 1.1 billion years ago (in the Proterozoic era), the first vertebrates - 450 million years ago (in the Silurian), cartilaginous fish - 400 million years ago (in the Devonian ), amphibians - 330 million years ago (also in the Devonian), reptiles - 300 million years ago (in the Carboniferous), mammals - 200 million years ago (Triassic, Mesozoic era) and later than all birds - 160 million years ago (Jurassic period).

Most marine animals are older than land animals.

It was in shallow water bodies that all types and classes of modern animals originated.

Evolution and modern composition of the flora and fauna of the Earth.

The first traces of the vital activity of organisms, as we already know, according to archeology, belong to the Archean period and were found in Archean rocks aged from 2.6 to 3.5 billion years. For almost three billion years before the beginning of the Paleozoic era, pre-nuclear organisms flourished on Earth - prokaryotes, bacteria and blue-green algae, evolution was extremely slow. The evolutionary explosion began in the Paleozoic era, which began 570 million years ago and ended 235 million years ago, and continued into the Mesozoic (235-66 million years ago). In the Paleogene period (235-66 million years ago), the last, Cenozoic era, warm-blooded animals became widespread in the fauna - mammals and birds, whose life was already less dependent on the influence of a changing habitat, and in the aquatic environment - bony fish that settled in sea and fresh waters, in the flora on land, angiosperms have won the dominant role plants.

The modern form of the flora and fauna of the Earth acquired after the last ice age - 10-12 thousand years ago.

In total, in the history of life on the planet, there were about 500 million species of living organisms, most of which died out long ago: the modern flora and fauna of the Earth has approximately 2.73 million known and described species

(the actual number is, of course, higher).

All modern living organisms on Earth are divided into two kingdoms - pre-nuclear organisms, Prokaryotes (Procariotae) and nuclear organisms, Eukaryotes (Eucariotae).

Only one kingdom, Drobyanki (Mycota), belongs to the super-kingdom of Prokaryotes, uniting the departments of bacteria and blue-green.

The kingdom of Eukaryotes includes three kingdoms - plants (Vegetabilia), animals (Animalia) and Fungi (Fungi).

In the modern era, there are approximately 5,000 known species prokaryotes, including 3 thousand species of bacteria and 2 thousand species of blue-green (only 0.2% of the total number of species).

The total number of known eukaryotic species is approximately 2727 thousand species (99.8%), including 352 thousand known plant species (12.9%), 2274 thousand known animal species (83.2%), and about 101 thousand known species of mushrooms (3.7%).

Most of the plants are flowering (about 250 thousand species). from animals - arthropods (1.5 million species), including insects (1 million species), roundworms (0.5 million species), mollusks (107 thousand species) and chordates (41-46 thousand species). species).

Data on the presence of the main groups of living organisms on Earth in marine, fresh waters and on land, as well as information on the total number of species by groups and the estimated era of origin (the most ancient finds) are presented in Table 2.

Table 2.

The main taxonomic groups of modern living organisms, their occurrence on land, in marine and fresh waters, a rough estimate of the number of species and epoch of origin.

Note: the presence of a particular group is marked with a “+” sign

Table 3. Distribution of the approximate number of species described by science by the kingdoms of Drobyanok, Mushrooms, Plants and Animals, in thousand species and in %%.

Thus (Table 2), out of 38 large taxa (divisions, types), representatives of 14 taxa live only in the hydrosphere, representatives of 16 taxa live in the hydrosphere and on land, and only 8 taxa live only on land.

The oceans are the most important, the main part of the biosphere of our planet,

in which life is represented from the surface to the deepest depths in more forms than in fresh water and on land. In general, the hydrosphere is the cradle of life.

Exploring the ways development of life forms on Earth, most modern biologists believe that they develop as evolutionarily , and spasmodically . The theory of “punctuated equilibrium” by E. Mayr and D. Simpson proves that “massive rearrangements of floras and faunas occur during periods of restructuring of the face of the Earth” (Nikolsky, 1980). Favorable conditions for the emergence of new species and higher taxa are usually created during periods of increased tectonic activities on Earth, transgression and regression of the seas and oceans, climate change, and, in addition, some researchers believe that jumps in the evolution of life on Earth are associated with the appearance of supernovae every 50 million years, creating a radiation dose of 200-500 P (about 1/2 of the lethal dose for humans, according to Calvin, 1971).

In addition, according to the theory of Ch. Darwin, the types of living organisms can change gradually, using the mechanisms natural selection and gradually improving by adapting to changing environmental conditions.

It is noteworthy that many systematic groups of living organisms, which are very distant from each other, as a result of the same adaptation to the environment, experience convergent evolution, that is, they acquire similar features of the external and internal structure. For example, in the ocean, these are sharks (cartilaginous fish class), tuna (bone fish class) and dolphins (mammal class), which, as a result of independent convergent evolution, have acquired a number of common features (body shape, structure and shape of fins, etc.) . great value to understand the patterns of development of life forms on our planet, N.I. Vavilov’s teaching on homological series also has, which proved that genetically close species and genera of plants in completely different regions of the Earth have similar hereditary variability and are prone, probably, to a parallel directed evolution.

Thus, we see that in the development of nature there is a certain expediency, its improvement and adaptation to changing environmental conditions, that is, evolution is an irreversible and directed development of wildlife, accompanied by changes in the gene pools of populations and species, the formation of adaptations, extinction and the formation of new species, transformation of biocenoses and the biosphere as a whole (see the evolution of species, ecosystems and the biosphere).

The origin of life on Earth occurred about 3.8 billion years ago, when education ended earth's crust. Scientists have found that the first living organisms appeared in the aquatic environment, and only after a billion years did the first creatures come to the surface of the land.

The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants, the ability to reproduce by spores. Animals have also evolved significantly and adapted to life on land: internal fertilization, the ability to lay eggs, pulmonary respiration. An important milestone development was the formation of the brain, conditioned and unconditioned reflexes, survival instincts. The further evolution of animals provided the basis for the formation of mankind.

The division of the history of the Earth into eras and periods gives an idea of ​​the features of the development of life on the planet in different time periods. Scientists emphasize significant events in the formation of life on Earth in separate periods of time - eras, which are divided into periods.

There are five eras:

• Archean;
• Proterozoic;
• Paleozoic;
• Mesozoic;
• Cenozoic.

The Archean era began about 4.6 billion years ago, when the planet Earth only began to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80 °, the radiation level exceeded the permissible limits, under such conditions the origin of life was impossible.

It is believed that about 4 billion years ago our planet collided with celestial body, and the result was the formation of the Earth's satellite - the Moon. This event became significant in the development of life, stabilized the axis of rotation of the planet, contributed to the purification of water structures. As a result, the first life originated in the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.

Proterozoic era lasted from about 2.5 billion years to 540 million years ago. Remains found unicellular algae, molluscs, annelids. Soil is starting to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, the bacteria that inhabit the seas began to release more and more O 2 into the atmosphere. When the amount of oxygen was at a stable level, many creatures took a step in evolution and switched to aerobic respiration.

Palaeozoic includes six periods.

Cambrian period(530 - 490 million years ago) is characterized by the emergence of representatives of all types of plants and animals. The oceans were inhabited by algae, arthropods, mollusks, and the first chordates (Haikouihthys) appeared. The land remained uninhabited. The temperature remained high.

Ordovician period(490 - 442 million years ago). The first settlements of lichens appeared on land, and the megalograpt (a representative of arthropods) began to come ashore to lay eggs. Vertebrates, corals, sponges continue to develop in the thickness of the ocean.

Silurian(442 - 418 million years ago). Plants come to land, and rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, sensory organs appear. Mountain building is underway, different climatic zones are being formed.

Devonian(418 - 353 million years ago). The formation of the first forests, mainly ferns, is characteristic. Bone and cartilaginous organisms appear in water bodies, amphibians began to land on land, new organisms are formed - insects.

Carboniferous period(353 - 290 million years ago). The appearance of amphibians, the sinking of the continents, at the end of the period there was a significant cooling, which led to the extinction of many species.

Permian period(290 - 248 million years ago). The earth is inhabited by reptiles, therapsids appeared - the ancestors of mammals. The hot climate led to the formation of deserts, where only resistant ferns and some conifers could survive.

Mesozoic era divided into 3 periods:

Triassic(248 - 200 million years ago). The development of gymnosperms, the appearance of the first mammals. The division of land into continents.

Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The emergence of the ancestors of birds.

Cretaceous period(140 - 65 million years ago). Angiosperms (flowering) became the dominant group of plants. Development higher mammals, real birds.

Cenozoic era consists of three periods:

Lower Tertiary period or Paleogene(65 - 24 million years ago). The disappearance of the majority cephalopods, lemurs and primates appear, later parapithecus and dryopithecus. Ancestor development modern species mammals - rhinos, pigs, rabbits, etc.

Upper Tertiary or Neogene(24 - 2.6 million years ago). Mammals inhabit land, water and air. The emergence of Australopithecus - the first ancestors of humans. During this period, the Alps, the Himalayas, the Andes were formed.

Quaternary or Anthropogene(2.6 million years ago - today). A significant event of the period is the appearance of man, first Neanderthals, and soon Homo sapiens. vegetable and animal world acquired modern features.