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Archean era - the most ancient, most early period history of the earth's crust. AT archean era the first living organisms arose. They were heterotrophs and used organic compounds as food. The end of the Archean era is the time of the formation of the earth's core and a strong decrease in volcanic activity, which allowed the development of life on the planet.

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The Archean era, which began about 4 billion years ago, lasted about 1.5 billion years. The Archean era is divided into 4 periods: Eoarchean, Paleoarchean, Mesoarchean, Neoarchean

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Earth's crust

The lower period of the Archean era - Eoarchean 4 - 3.6 billion years ago. About 4 billion years ago. the earth was formed as a planet. Almost the entire surface was covered with volcanoes and rivers of lava flowed everywhere. Lava, erupted in large quantities, formed continents and oceanic depressions, mountains and plateaus. Permanent volcanic activity, impacts high temperatures and high pressure led to the formation of various minerals: various ores, building stone, copper, aluminum, gold, cobalt, iron, radioactive minerals and others. Approximately 3.8 billion years ago the first reliably confirmed igneous and metamorphic rocks such as granite, diorite and anorthosite were formed on Earth. These rocks were found in a wide variety of places: on the island of Greenland, within the Canadian and Baltic shields, etc.

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The next period of the Archean era - Paleoarchaean 3.6 - 3.2 billion years ago. It is the time of the formation of the first supercontinent in the history of the Earth - Valbara and a single World Ocean, which changed the structure of the crests of oceanic ridges, which led to the process of increasing the amount of water on Earth, and the amount of CO2 in the atmosphere began to decline.

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The Paleoarchean is followed by the Mesoarchean 3.2 - 2.8 billion years ago. Approximately 2.8 billion years ago, the first supercontinent in the history of the Earth began to split.

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Slide 10

Neoarchean 2.8 - 2.5 billion years ago - the last period of the Archean era, which ended 2.5 billion years ago, is the time of formation of the main mass of the continental crust, which indicates the exceptional antiquity of the Earth's continents.

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Atmosphere and climate of the Archean era

At the very beginning of the Archean era, there was little water on Earth, instead of a single ocean, there were only shallow pools that were not connected to each other. The atmosphere of the Archean era consisted mainly of carbon dioxide CO2 and its density was much higher than the current one. Due to the carbonic atmosphere, the water temperature reached 80-90°C. The nitrogen content was low, on the order of 10-15%. There was almost no oxygen, methane and other gases. The temperature of the atmosphere reached 120°С

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Flora and fauna of the Archean era

The Archean era is the time of the birth of the first organisms. The first inhabitants of our planet were anaerobic bacteria. The most important stage in the evolution of life on Earth is associated with the emergence of photosynthesis, which causes the separation organic world to plant and animal. The first photosynthetic organisms were prokaryotic (pre-nuclear) cyanobacteria and blue-green algae. The eukaryotic green algae that then appeared released free oxygen from the ocean into the atmosphere, which contributed to the emergence of bacteria capable of living in an oxygen environment. At the same time - on the border of the Archean Proterozoic era, two more major evolutionary events occurred - the sexual process and multicellularity appeared. Haploid organisms (bacteria and blue-greens) have one set of chromosomes. Each new mutation immediately manifests itself in their phenotype. If the mutation is beneficial, it is retained by selection; if it is harmful, it is eliminated by selection. Haploid organisms continuously adapt to the environment, but they do not develop fundamentally new features and properties. The sexual process dramatically increases the possibility of adapting to environmental conditions, due to the creation of countless combinations in chromosomes.

Sections: Biology

Tasks: to acquaint students with the chronology of the development of wildlife and the main aromorphoses that occurred in the animal and plant kingdoms in the Archean and Proterozoic eras

Equipment: computer, multimedia installation, options test items(1 and 2), sets of additional literature, teacher's presentation ( Attachment 1), student presentations ( application 2, appendix 3), a commentary on the student presentation ( annex 4).

During the classes

I. Org. moment (distribution of students into groups for further work)

II. Checking the initial knowledge

III. New topic

Today, guys, we will take a trip to the beginning of time. We will try to see and find out how the development of the Earth proceeded, what events took place on it millions, or even billions of years ago. What organisms and how appeared on Earth, how they replaced each other, in what ways and with the help of which evolution took place. Unfortunately, the time of our journey is limited and today we will be able to visit only the first eras of the Earth's development.

So, the topic of our lesson "The development of life in the Archean and Proterozoic eras". (WRITE THE TOPIC IN THE NOTEBOOK) (SLIDE 1)

Before starting to study new topic, i.e. to go on a journey, let's do a little test and evaluate it, finding out at the same time whether you have enough stock of knowledge to "travel" through the history of the Earth.

In the workbooks, put the option and do the test work. (two options that are distributed in advance to the desks).

Mutual verification.

Now exchange notebooks and check each other's work, putting 1 point for each correct answer. (SLIDE 2 with answers)

So, you have assessed the level of each other's knowledge, someone has it better, someone has it worse, but nevertheless time does not wait, we will move on. After all, the strong always help the weak along the way.

Teacher's story, accompanied by presentation slides.

Development of life on Earth.

“Time is long,” said James Hutton, and indeed, it took an incredibly long time to complete the titanic and amazing transformations that have taken place on our planet. Making a flight to spaceship about 4 billion years ago, in that part of the Universe where our Sun is located today, we would have observed a picture different from that which astronauts see today. Recall that the Sun has its own moving speed - about two tens of kilometers per second; and then it was in another part of the Universe, and the Earth at that time was just born ...

So, the Earth was just born and was in the initial stage of its development. She was a red-hot little ball swaddled in swirling clouds, and lullaby it was the roar of volcanoes, the hiss of steam and the roar of gale-force winds.

The earliest rocks that could have formed during this turbulent infancy were volcanic rocks, but they could not remain unchanged for long, being subjected to violent attacks of water, heat and steam. The earth's crust caved in, and fiery lava poured on them. The traces of these terrible battles are in the rocks of the Archean era - the most ancient rocks known to us today. Basically, these are shales and gneisses that occur in deep layers and are exposed in deep canyons, mines, and quarries.

In such rocks - they were formed about one and a half billion years ago - there is almost no evidence of life.

The history of living organisms on Earth is studied by the remains, imprints and other traces of their life activity preserved in sedimentary rocks. This is what science does paleontology. For convenience of study and description, the entire history of the Earth is divided into periods of time that have different durations and differ from each other in climate, the intensity of geological processes, the appearance of some and the disappearance of other groups of organisms, etc.

The names of these periods of time Greek origin. The largest such divisions are AEONS, there are two of them -cryptozoic (hidden life) andphanerozoic(clear life). Eons are divided into eras. There are two eras in the Cryptozoic - the Archean (the oldest) and the Proterozoic (primary life). Phanerozoic includes three eras - Paleozoic (ancient life), Mesozoic ( average life) and Cenozoic (new life). In turn, eras are divided into periods, periods are sometimes divided into smaller parts.(SLIDE 3).

The scheme must be transferred to the notebook after the teacher's explanation.

According to scientists, planet Earth was formed 4.5-7 billion years ago. About 4 billion years ago, the earth's crust began to cool and harden, and conditions arose on Earth that allowed living organisms to develop.

No one knows exactly when the first living cell arose. The age of the earliest traces of life (the remains of bacteria) found in ancient deposits of the earth's crust is about 3.5 billion years. Therefore, presumably the age of life on Earth is 3 billion 600 million years. (SLIDE 4)

Imagine that this huge period of time fit within one day. Now our "clock" is exactly 24 hours, and at the time of the emergence of life it showed 0 hours. Each hour contained 150 million years, each minute - 2.5 million years.

The most ancient epoch in the development of life - the Precambrian (Archaean + Proterozoic) lasted an incredibly long time: over 3 billion years. (from the beginning of the day until 8 pm). (SLIDE 5)

So what was happening at that time?

By this time, the first living organisms were already in the aquatic environment.

The living conditions of the first organisms: (SLIDE 6)

• food - "primary soup" + less fortunate brothers.
• Millions of years => the broth is getting "thinner"
• Depletion of nutrient reserves
• The development of life has come to a standstill.

But evolution found a way out: (SLIDE 7)

1. The appearance of bacteria capable of converting inorganic substances into organic substances with the help of sunlight.
2. Need hydrogen => decompose hydrogen sulfide (to build organisms). Green plants get it by splitting water and releasing oxygen, but bacteria do not yet know how to do this. (Decomposing hydrogen sulfide is much easier)
3. Limited amount of hydrogen sulfide => crisis in the development of life
4. A "way out" has been found - blue-green algae have learned to split water into hydrogen and oxygen (this is 7 times more difficult than splitting hydrogen sulfide). This is a real feat! (2 billion 300 million years ago - 9 am) (SLIDE 8)

• Oxygen is a by-product. Accumulation of oxygen → life threatening. ( Oxygen is essential for most modern species, but it has not lost its dangerous oxidizing properties. The first photosynthetic bacteria, enriching the environment with it, in fact poisoned it, making it unsuitable for many of their contemporaries.)
• From 11 o'clock in the morning - a new spontaneous generation of life on Earth became impossible.
• Oxygen content = 1%.
• The problem is how to deal with the increasing amount of this aggressive substance?
• Victory - the appearance of the first organism that inhaled oxygen - the emergence of respiration. (SLIDE 9)
  (Organisms coped with the threat of oxygen in several ways. Some (aerobes) learned to breathe, that is, to receive energy due to the oxygen oxidation of organic matter. This protected them from excess oxygen and at the same time balanced its supply to environment through photosynthesis. Others (anaerobes) hid from the dangerous oxidizing agent where there is almost none.
• Life in the ocean - protection from UV rays.
  (At that time, the Earth was exposed to harsh UV rays and life was possible only in the water column. Photosynthesis led to a dramatic change chemical composition earthly environment. As long as the release of oxygen exceeded its consumption, it accumulated in the water and atmosphere, which led to another important consequence for the evolution of life. In the upper layers of the atmosphere, oxygen molecules (O 2) under the influence of cosmic radiation give ozone (O 3), which forms a continuous layer in the stratosphere and absorbs the part of the ultraviolet emitted by the Sun that is dangerous for living.)
• Oxygen => formation of the ozone layer(radiation softening)
• Exit of life to land.
  With the release of life on land, evolution on Earth literally marched "by leaps and bounds"
• More "inventions" of nature: 14 hours - cells received a nucleus + sexual reproduction (a sharp acceleration in the rate of evolution) + the appearance of the first multicellular creatures. (SLIDE 10)
• The end of the Precambrian (20 hours): a variety of animals - jellyfish, flatworms, sponges, polyps. (soft-bodied, devoid of a skeleton) (SLIDE 11)
• The appearance of the skeleton - shells, shells

A NEW GEOLOGICAL ERA HAS STARTED.

Teacher: You will learn more about the Archean and Proterozoic from the messages (with presentations) of the guys and your independent work with additional literature (materials).

Before starting work, students divided into groups receive questions and assignments. Their task is to listen to the performances of the guys, work with additional materials and answer questions by choosing one speaker from the group.

Independent work with a textbook and additional literature. It is necessary to review the information provided and find answers to questions.

QUESTIONS

1 team

2 team

1. Arrange the events occurring in the Archaean and Proterozoic in the sequence corresponding to the order of their occurrence:
   a) the appearance of photosynthesis;
   b) the appearance of prokaryotes;
   c) the appearance of multicellular algae;
   d) the appearance of free oxygen;
   e) the appearance of arthropods;
   f) the appearance of mollusks;
   g) the appearance of annelids.
   Answer: b, a, d, c, g, e, f
2. What is the reason for the outbreak of diversity of living organisms in the Proterozoic?

3 team

1. How did the activity of living organisms affect the change in the geological shells of the Earth?
2. Fill the table:

Speech by the guys, viewing presentations.

(Presentation 2 "Archaean". Presentation 3 "Proterozoic")

Group presentations.

Recording in the notebook of the events of the Archean and Proterozoic. (SLIDES 12-13)

Anchoring

Writing a small final test and its self-examination (the text of the test can be distributed to students, can be displayed on the screen).

Final test.

1. The geological history of the Earth began about ... billion years ago.
2. The first living organisms according to the method of nutrition were ...
3. The era in the history of the Earth, the name of which is translated as "the most ancient" ....
4. An important stage in the evolution of life, which led to the division of the world into plant and animal ....
5. The longest era...
6. Two major events on the boundary of the Archaean - Proterozoic ....
7. Life became possible on land thanks to the emergence of ...

Self-test - swap notebooks and check the tests by key.

Answers to the test: (SLIDE 14)

1. 3.5 billion years ago
2. heterotrophs
3. Archean
4. photosynthesis
5. Proterozoic
6. sexual process and multicellularity
7. ozone layer

Summing up the lesson

(SLIDE 15) The teacher shows on the screen the main results of the evolutionary process (what happened), and the students name an event that occurred during the Archean and Proterozoic eras.

Archean era- this is the first stage in the development of life on earth, an exciting time interval of 1.5 billion years. It originates 4 billion years ago. During the Archean era, the flora and fauna of the planet begin to emerge, from here the history of dinosaurs, mammals and humans begins. The first deposits of the natural wealth of nature appear. There were no mountain heights and the oceans, there was not enough oxygen. The atmosphere was mixed with the hydrosphere into a single whole - this prevented the sun's rays from reaching the earth.

The Archean era in translation from ancient Greek means "ancient". This era is divided into 4 periods - Eoarchean, Paleoarchean, Mesoarchean and Neoarchean.

The first period of the Archean era lasted approximately 400 million years. This period is characterized by increased meteor showers, the formation of volcanic craters and the earth's crust. Active formation of the hydrosphere begins, salty reservoirs isolated from each other appear with hot water. The atmosphere is dominated by carbon dioxide, the air temperature reaches 120 °C. The first living organisms appear - cyanobacteria, which begin to produce oxygen through photosynthesis. Vaalbara, the main terrestrial continent, is being formed.

paleoarchaean

The next period of the Archean era captures a period of time of 200 million years. The Earth's magnetic field is enhanced by increasing the hardness of the Earth's core. This favorably affects the conditions of life and development of the simplest microorganisms. Days last about 15 hours. The oceans are being formed. Changes in submarine ridges lead to a slow increase in the volume of water and a decrease in the amount of carbon dioxide in the atmosphere. The formation of the first terrestrial continent continues. Mountain ranges do not yet exist. Instead, active volcanoes rise above the ground.

Mesoarchean

The third period of the Archean era lasted 400 million years. At this time, the main continent split into 2 parts. As a result of a sharp cooling of the planet, in which constant volcanic processes are to blame, the Pongol glacial formation is formed. During this period, the number of cyanobacteria begins to actively grow. Chemolithotrophic organisms develop that do not need oxygen and sunlight. Vaalbar is fully formed. Its size is approximately equal to the size of modern Madagascar. The formation of the Ur continent begins. Large islands slowly begin to form from volcanoes. The atmosphere is still dominated by carbon dioxide. The air temperature remains high.

The last period of the Archean era ended 2.5 billion years ago. At this stage, the formation of the earth's crust is completed, the level of oxygen in the atmosphere increases. The mainland of Ur becomes the basis of Kenorland. Most of the planet is occupied by volcanoes. Their vigorous activity leads to increased formation of minerals. Gold, silver, granites, diorites and other equally important natural resources were formed during the Neoarchean period. AT last centuries of the Archean era the first multicellular organisms appear, which later divided into terrestrial and marine inhabitants. Bacteria begin the development of the sexual process of reproduction. Haploid microorganisms have one chromosome set. They are constantly adapting to changes in their environment, but they do not have other properties. The sexual process allowed adaptation to life with changes in the set of chromosomes. This made it possible for the further evolution of living organisms.

Flora and fauna of the Archean era

The flora of this era cannot boast of diversity. The only kind Plants are unicellular filamentous algae - spheromorphids - the habitat of bacteria. When these algae form in colonies, they can be seen without special instruments. They can go free swimming or attach themselves to the surface of something. In the future, algae will form new form life - lichens.

During the Archean era, the first prokaryotes- single-celled organisms that do not have a nucleus. With the help of photosynthesis, prokaryotes produce oxygen and create favorable conditions for the emergence of new forms of life. Prokaryotes are divided into two domains - bacteria and archaea.

Archaea

It has now been established that they have features that distinguish them from other living organisms. Therefore, the classification that combines them with bacteria in one group is considered outdated. Outwardly, archaea are similar to bacteria, but some have unusual shapes. These organisms can absorb both sunlight and carbon. They can exist in the most unsuitable conditions for life. One type of archaea is food for marine life. Several species have been found in the human intestine. They take part in the processes of digestion. Other species are used to clean sewage ditches and ditches.

There is an unconfirmed theory that during the Archean era, the emergence and development of eukaryotes, microorganisms of the kingdom of fungi, similar to yeast fungi, occurred.

The fact that life on earth originated during the Archean era is evidenced by the found fossilized stromalites - waste products of cyanobacteria. The first stromatolites were discovered in Canada, Siberia, Australia and Africa. Scientists have proven that it was bacteria that had a huge impact on the formation of aragonite crystals, which is found in mollusk shells and is part of corals. Thanks to cyanobacteria, deposits of carbonate and siliceous formations arose. Colonies of ancient bacteria look like mold. They were located in the area of ​​volcanoes, and at the bottom of lakes, and in coastal areas.

Archean climate

Scientists have not yet been able to learn anything about the climatic zones of this period. The existence of zones of different climates in the Archean era can be judged by ancient glacial deposits - tillites. The remains of glaciations are now found in America, Africa, and Siberia. It is not yet possible to determine their true dimensions. Most likely, glacial deposits covered only the mountain peaks, because the vast continents during the Archean era had not yet been formed. The existence of a warm climate in some areas of the planet is indicated by the development of flora in the oceans.

Hydrosphere and Atmosphere of the Archean Era

In the early period, there was little water on earth. The water temperature during the Archean era reached 90°C. This indicates the saturation of the atmosphere with carbon dioxide. There was very little nitrogen in it, there was almost no oxygen in the early stages, the remaining gases are quickly destroyed under the influence of sunlight. The temperature of the atmosphere reaches 120 degrees. If nitrogen prevailed in the atmosphere, then the temperature would not be lower than 140 degrees.

In the late period, after the formation of the world ocean, the level of carbon dioxide began to decrease markedly. The water and air temperature also dropped. And the amount of oxygen increased. Thus, the planet gradually became habitable for various organisms.

Minerals of Archaea

It is in the Archean era that the greatest formation of minerals occurs. This is facilitated by the active activity of volcanoes. Colossal deposits of iron, gold, uranium and manganese ores, aluminum, lead and zinc, copper, nickel and cobalt ores were laid by this era of the life of the earth. Within the territory of Russian Federation Archean deposits have been found in the Urals and Siberia.

In details periods of the archean era will be discussed in the next lectures.

life in the Archean era MOU "Poksheng Basic School No. 21" Completed by: Amosov Anton Teacher: Bogdanova L.V.

Duration Archean, Archean era - geological eon. The upper boundary of the Archean is taken to be about 2.5 billion years ago (±100 million years). Beyond the lower boundary, approximately - 3.8-4 billion years ago. The duration of the Archean is approximately 1.5 billion years.

Archean Era Periods: Eoarchean Paleoarchean Mesoarchean Neoarchean

Climate and environment Active volcanic activity. Anaerobic (oxygen-free) living conditions in a shallow ancient sea. Development of an oxygen-containing atmosphere.

Development of the organic world In the Archean era, the first living organisms arose. They were heterotrophs and used organic compounds of the "primary" broth" as food. The first inhabitants of our planet were anaerobic bacteria. The most important stage in the evolution of life on Earth is associated with the emergence of photosynthesis, which leads to the division of the organic world into flora and fauna. The first photosynthetic organisms were prokaryotic (pre-nuclear) cyanobacteria and blue-green algae. The eukaryotic green algae that then appeared released free oxygen into the atmosphere from the ocean, which contributed to the emergence of bacteria capable of living in an oxygen environment.

Flora and fauna In the Archean deposits there is no skeletal fauna, which serves as the basis for constructing the Phanerozoic stratigraphic scale, nevertheless, there are quite a lot of various traces of organic life. The fauna of the Archean is much poorer than the flora. Separate indications of the presence of animal remains in the Archean rocks refer to objects that, apparently, are of inorganic origin or are products of stromatolite leaching.

Conclusion 1 Life originated on Earth from organic molecules synthesized abiogenically. 2. In the Archean era, on the border with the Proterozoic, the emergence of the first cells marked the beginning of biological evolution.

Eoarchean Eoarchean - the lower period of the Archean era, covering the time interval from 4 to 3.6 billion years ago. Eoarchean is remarkable in that it is the time of the formation of the hydrosphere and the discovery of the alleged remains of the first prokaryotes, stromatolites and ancient rocks. At the very beginning of the Archean era, there was little water on Earth, instead of a single ocean, there were only scattered shallow basins. The water temperature reached 70-90 ° C, which could be observed only if the Earth at that time had a dense carbon dioxide atmosphere.

Paleoarchean Paleoarchean - the period following the Eorcheian, is the time of the formation of the first supercontinent in the history of the Earth - Vaalbara and a single World Ocean, which overlapped the crests of the mid-ocean ridges. As a result, the hydration of the basaltic oceanic crust noticeably increased, and the rate of increase in the partial pressure of CO2 in the Late Archean atmosphere somewhat decreased. The first reliable remains of living organisms (bacteria) and traces of their vital activity also belong to this time. The duration of the Paleoarchean is 400 million years.

Mesoarchean The Mesoarchean lasted from 3.2 to 2.8 billion years ago. Here the period of the split of Vaalbara and widespread fossils of ancient life forms.

Neoarchean Neoarchean - the last period of the Archean era, which ended 2.5 billion years ago, is the time of formation of the main mass of the continental crust, which indicates the exceptional antiquity of the Earth's continents.