What living organisms were the first on earth. When did the first living organisms appear on Earth? The oldest trees

The first living organisms arose in the Archean era. They were heterotrophs and used organic compounds from the “primary broth” as food. First the 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 determines the division of the organic world into plant and animal. The first photosynthetic organisms were prokaryotic (prenuclear) cyanobacteria and blue-green algae. 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. At the same time, on the border of the Archean Proterozoic era, two more major evolutionary events occurred - sexual process and multicellularity.

To more clearly imagine the meaning of the last two aromorphoses, let us dwell on them in more detail. Haploid organisms (microorganisms, blue-green) have one set of chromosomes. Each new mutation immediately manifests itself in their phenotype. If a mutation is beneficial, it is preserved by selection; if it is harmful, it is eliminated by selection. Haploid organisms continuously adapt to their environment, but they do not develop fundamentally new characteristics and properties. The sexual process dramatically increases the possibility of adaptation to environmental conditions, due to the creation of countless combinations in chromosomes. Diploidy, which arose simultaneously with the formed nucleus, allows mutations to be preserved in a heterozygous state and used as reserve of hereditary variability for further evolutionary transformations. In addition, in the heterozygous state, many mutations often increase the viability of individuals and, therefore, increase their chances in the struggle for existence.

The emergence of diploidity and genetic diversity of unicellular eukaryotes, on the one hand, led to the heterogeneity of cell structure and their association in colonies, on the other hand, the possibility of “division of labor” between the cells of the colony, i.e. formation of multicellular organisms. The separation of cell functions in the first colonial multicellular organisms led to the formation of primary tissues - ectoderm and endoderm, which later made it possible for the emergence of complex organs and organ systems. Improving the interaction between cells, first contact, and then with the help of nervous and endocrine systems ensured the existence of multicellular

the body as a whole.

The paths of evolutionary transformations of the first multicellular organisms were different. Some switched to a sedentary lifestyle and turned into organisms like sponges. Others began to crawl with the help of cilia. From them came flatworms. Still others retained a swimming lifestyle, acquired a mouth and gave rise to coelenterates.

3. The history of the Earth, from the time of the appearance of organic life on it and until the appearance of man on it, is divided into three large periods - eras, sharply different from one another, and bearing the names: Paleozoic - ancient life, Mesozoic - middle, Neozoic - new life .

Of these, the largest in time is the Paleozoic; it is sometimes divided into two parts: the early Paleozoic and the late, since the astronomical, geological, climatic and floristic conditions of the late are sharply different from the early. The first includes: the Cambrian, Silurian and Devonian periods, the second - the Carboniferous and Permian.

Before the Paleozoic there was the Archean era, but there was no life then. The first life on Earth is algae and plants in general. The first algae originated in water: so it seems modern science the emergence of the first organic life, and only later do mollusks appear that feed on algae.

Algae turn into ground grass, giant grasses turn into grass-like trees of the Paleozoic.

During the Devonian period, lush vegetation appeared on Earth, and life in the water appeared in the form of its small representatives: protozoa, trilobites, etc. Warm climate - on everything globe, for there is not yet a modern sky with its sun, moon and stars; everything was covered with a thick, weakly permeable, powerful fog of water vapor, which still surrounded the earth in colossal quantities, and only part of it settled in the water basins of the oceans. The earth rushes through the cold cosmic space, but then it was dressed in a warm, impenetrable shell. Due to the greenhouse (greenhouse) effect, the entire early Paleozoic, including even the Carboniferous period, had warm-water flora and fauna throughout the earth: both on Spitsbergen and in Antarctica there were deposits of coal, which is a product of the tropical forest, everywhere, and there was warm-water marine fauna everywhere. Then the rays of the sun did not penetrate directly onto the earth, but were refracted at a certain angle through the vapor and illuminated it then differently than now: the night was not so dark and not so long, and the day was not so bright. The days were shorter than today. There was neither winter nor summer, there are still no astronomical or geophysical reasons for this. Coal deposits consist of trees that do not have tree rings, their structure is tubular, like grass, and not ring-shaped. This means there were no seasons. There were no climate zones, also due to the greenhouse effect.

Modern paleontology has already sufficiently studied all types of living organisms of the Cambrian period: about a thousand various types mollusks, but there is reason to believe that the first vegetation and even the first mollusks appeared at the end of the Archean era.

In the next, Silurian period, the number of mollusks increases to 10,000 varieties, and in the Devonian period lungfishes appear, that is, fish that do not have a backbone, but are covered with a shell, as a transitional form from mollusks to fish. They breathed with both gills and lungs. They make an attempt to become land dwellers, but they are not the ones who have to do it. The transition from sea to land is carried out by amphibians, from the class of vertebrates such as amphibious lizards.

The first representative of lizards - the archaeosaur - appears at the end of the Paleozoic, and begins to develop at the beginning of the Mesozoic era, during the Triassic period.

Distinctive properties of the Paleozoic: light was not separated from darkness; the intermediate state, between light and darkness, between day and night, was partially extended until the beginning of the Carboniferous. There were no luminaries visible in the sky. There were no seasons or climate zones.

Proof: the absence of growth rings on Paleozoic trees, except for the last, Permian period, when they first appeared; the disappearance from that time of all herbaceous trees with a tubular trunk structure; the spread of tropical vegetation over the entire surface of the earth, including the poles; the same heat-loving fauna throughout the earth; the formation of gigantic quantities of coal deposits as a result of the death of grass-like forests, not adapted to the direct rays of the sun and naturally charred and killed by ultraviolet and solar radiation, just as grass is charred in a hot summer during drought.

Since the Permian period, climatic zones and the distribution of later flora and fauna appeared, differently adapted to the climatic zones.

The next period in the life of the Earth corresponds to the entire Mesozoic era, that is, the periods: Triassic, Jurassic and Cretaceous. This was the heyday of the animal kingdom. The most diverse and bizarre forms of reptiles inhabited the Earth. They were both in the seas, on land and in the air. It should be noted that the entire class of insects appeared at the end of the Paleozoic, and they were many times larger than their modern descendants.

The first birds appear in the Jurassic period. They multiplied not only quantitatively, but also into a variety of species. One species of bird gave birth to chicks with their own characteristics, which gave rise to a new species of bird, which in turn gave birth to chicks that were not entirely similar to them. This is how the diverse world of living beings developed. At some moments there were absolutely amazing metamorphoses.

Paleontologists know many specimens of different stages in the development of birds and not a single intermediate species between them: these are pterodactyls, archeopteryxes and fully developed birds.

Pterodactyls are half birds, half reptiles. This is a lizard whose toes have greatly developed and membranes have appeared between them, like those of a bat. But the next generation, which retained the same long spine, on both sides of which feathers grew, differs sharply from its predecessors. The body and wings were covered with feathers, but claws remained on the wings for clinging to branches.

The head of Archeopteryx is a beast's muzzle, inherited from a pterodactyl, with sharp large teeth and soft lips. And only in the next generation the vertebral tail disappears and the head becomes the head of a bird with a beak.

The last era is coming - the Neozoic. It includes the Tertiary and glacial (Quaternary) periods. Man appears towards the end of the Ice Age. It was during the Neozoic era that mammals appeared. This is almost the modern world of animals. The fauna of that time can be seen to some extent in Africa, which was not touched by the glacier.

The biggest question for many is the question of monkeys. Most scientists are inclined to believe that the ape can in no way be the predecessor of man; but some say there must be some common ancestor. But this common ancestor has not yet been found.

Geochronological table of the Earth

Cyanobacteria
Fossils of cynobacteria dating back 3.5 billion have been discovered in Western Australia. Cyanobacteria, or blue-green algae, is a type of bacteria capable of photosynthesis. It is believed that this played a role in the formation of the Earth's atmosphere and made it suitable for life.

Sponges
Sponges appeared 580 million years ago. Such ancient representatives were found in Australia, China and Mongolia.

Jellyfish
Jellyfish appeared 505 million years ago and belong to the group of coelenterates. This group also includes corals, sea anemones and other sea inhabitants.

Horseshoe crabs
Appeared 450 million years ago. Horseshoe crabs are considered living fossils. These arthropods live in shallow ocean waters with soft sandy or muddy bottoms.

Coelacanth
This rare fish appeared 400 million years ago. The last specimen was caught in 1998.

Ginkgo
Originating 270 million years ago, Ginkgo is the only living member of the ginkgo plant. Geological disasters almost completely wiped out this species from the face of the Earth.

Nautilus
Another living fossil, born 235 million years ago. Nautilus appeared at the end of the Triassic period. Nautiluses are found in the western Pacific Ocean.

Sturgeons
Sturgeons appeared 200 million years ago and are also among the living fossils, although they have changed during the process of evolution.

Martialis Heureka
This most primitive species of ants arose 100 million years ago and has remained virtually unchanged during all this time. The species was discovered in the Amazon in 2000. Ants live underground.

Question 1. Which plants are classified as lower? What is their difference from the higher ones?

Lower plants include a variety of algae. Distinctive feature algae from higher plants, is the lack of differentiation into tissues and organs (leaves, stem and root). The body of algae consists of a single cell or multicellular.

Question 2. Which group of plants currently dominates our planet?

Currently, plants called angiosperms, or flowering plants, occupy a dominant position on our planet.

Question 1. Based on what data can we say that the plant world developed and became more complex gradually?

If you trace how the structure of plants from algae to flowering plants becomes more complex, what are the methods of reproduction, what tissues and organs appear, where they live. We can say that as life developed on Earth, the plant world developed and became more complex gradually. Algae do not have tissues or organs. In higher spores, a prototype of tissues and organs appears. In gymnosperms and flowering plants these tissues become more complex. Reproduction methods become more complex, from simple cell division in algae to double fertilization in flowering plants. Algae live in water, mosses live in a humid environment, angiosperms live both in water and on land (there is also enough precipitation).

Question 2. Where did the first living organisms appear?

The first living organisms appeared in water approximately 3.5-4 billion years ago. The simplest single-celled organisms were similar in structure to bacteria.

Question 3. What was the significance of the appearance of photosynthesis?

With the advent of photosynthesis, oxygen began to accumulate in the atmosphere. The composition of the air began to gradually approach the modern one, that is, it mainly includes nitrogen, oxygen and a small amount of carbon dioxide. This atmosphere contributed to the development of more advanced forms of life.

Question 4. Under the influence of what conditions did ancient plants switch from an aquatic lifestyle to a terrestrial one?

The transition of plants to a terrestrial lifestyle was apparently associated with the existence of land areas that were periodically flooded and cleared of water (due to fluctuations in the earth’s crust). At this time, the globe had a humid and warm climate. The transition of some plants from an aquatic to a terrestrial lifestyle began. The structure of ancient multicellular algae gradually became more complex, and they gave rise to the first land plants.

Question 5. Which ancient plants gave rise to ferns, and which to gymnosperms?

From rhiniophyte-like plants came the ancient mosses, horsetails and ferns and, apparently, mosses, which already had stems, leaves, and roots.

At the end of the Carboniferous period, the Earth's climate almost everywhere became drier and colder. Tree ferns, horsetails and mosses gradually died out. Primitive gymnosperms appeared - descendants of some ancient fern-like plants. The origin of gymnosperms from ancient ferns proves many similarities between these plants.

Question 6. What is the advantage of seed plants over spore plants?

Plants that reproduced by seeds were better adapted to life on land than plants that reproduced by spores. This is due to the fact that the possibility of fertilization in them does not depend on the presence of water in the external environment. The superiority of seed plants over spore plants became especially clear when the climate became less humid.

Angiosperms developed generative organs—seeds, fruits, and flowers. Only their seeds develop inside the fruit and are protected by the pericarp. There are woody, shrubby and herbaceous forms.

Quests for the curious

In summer, explore the steep banks of rivers, the slopes of deep ravines, quarries, pieces of coal, and limestone. Find fossilized ancient organisms or their imprints. Sketch them. Try to determine which ancient organisms they belong to.

How did life originate on Earth? The details are unknown to humanity, but the cornerstone principles have been established. There are two main theories and many minor ones. So, according to the main version, organic components came to Earth from space, according to another - everything happened on Earth. Here are some of the most popular teachings.

Panspermia

How did our Earth appear? The biography of the planet is unique, and people are trying to unravel it different ways. There is a hypothesis that life existing in the Universe spreads through meteoroids (celestial bodies intermediate in size between interplanetary dust and an asteroid), asteroids and planets. It is assumed that there are life forms that can withstand exposure (radiation, vacuum, low temperatures and etc.). They are called extremophiles (including bacteria and microorganisms).

They fall into debris and dust, which are thrown into space after preserving, thus, life after the death of small bodies solar system. Bacteria can travel in a dormant state for long periods of time before another chance encounter with other planets.

They may also mix with protoplanetary disks (a dense cloud of gas around a young planet). If in a new place the “steadfast but sleepy soldiers” find themselves in favorable conditions, they become active. The process of evolution begins. The story is unraveled with the help of probes. Data from instruments that have been inside comets indicate: in the overwhelming majority of cases, the probability is confirmed that we are all “a little aliens,” since the cradle of life is space.

Biopoiesis

Here is another opinion regarding how life began. There are living and nonliving things on Earth. Some sciences welcome abiogenesis (biopoesis), which explains how, through natural transformation, biological life emerged from inorganic matter. Most amino acids (also called the building blocks of all living organisms) can be formed using natural chemical reactions, not related to life.

This is confirmed by the Muller-Urey experiment. In 1953, a scientist passed electricity through a mixture of gases and obtained several amino acids in laboratory conditions that simulated the conditions of the early Earth. In all living things, amino acids are transformed into proteins under the influence of genetic memory keepers, nucleic acids.

The latter are synthesized independently biochemically, and proteins accelerate (catalyze) the process. Which organic molecule is the first? And how did they interact? Abiogenesis is in the process of finding an answer.

Cosmogonic trends

This is the doctrine of in space. In the specific context of space science and astronomy, the term refers to the theory of the creation (and study) of the solar system. Attempts to gravitate toward naturalistic cosmogony do not stand up to criticism. Firstly, existing scientific theories cannot explain the main thing: how did the Universe itself appear?

Secondly, there is no physical model that explains the earliest moments of the existence of the Universe. The mentioned theory does not contain the concept of quantum gravity. Although string theorists say that elementary particles arise as a result of vibrations and interactions of quantum strings), those studying the origin and consequences of the Big Bang (loop quantum cosmology) do not agree with this. They believe they have formulas to describe the model in terms of field equations.

With the help of cosmogonic hypotheses, people explained the homogeneity of the movement and composition of celestial bodies. Long before life appeared on Earth, matter filled all space and then evolved.

Endosymbiont

The endosymbiotic version was first formulated by Russian botanist Konstantin Merezhkovsky in 1905. He believed that some organelles arose as free-living bacteria and were adopted into another cell as endosymbionts. Mitochondria evolved from proteobacteria (specifically Rickettsiales or close relatives) and chloroplasts from cyanobacteria.

This suggests that multiple forms of bacteria entered into symbiosis to form a eukaryotic cell (eukaryotes are cells of living organisms containing a nucleus). Horizontal transfer of genetic material between bacteria is also facilitated by symbiotic relationships.

The emergence of diversity in life forms may have been preceded by the Last Common Ancestor (LUA) of modern organisms.

Spontaneous generation

Until the early 19th century, people generally rejected "suddenness" as an explanation for how life began on Earth. The unexpected spontaneous generation of certain forms of life from inanimate matter seemed implausible to them. But they believed in the existence of heterogenesis (a change in the method of reproduction), when one of the life forms comes from another species (for example, bees from flowers). Classical ideas about spontaneous generation boil down to the following: some complex living organisms appeared due to the decomposition of organic substances.

According to Aristotle, this was an easily observed truth: aphids arise from dew that falls on plants; flies - from spoiled food, mice - from dirty hay, crocodiles - from rotting logs at the bottom of reservoirs, and so on. The theory of spontaneous generation (refuted by Christianity) secretly existed for centuries.

It is generally accepted that the theory was finally refuted in the 19th century by the experiments of Louis Pasteur. The scientist did not study the origin of life, he studied the emergence of microbes in order to be able to combat infectious diseases. However, Pasteur's evidence was no longer controversial, but strictly scientific in nature.

The Clay Theory and Sequential Creation

The emergence of life based on clay? Is it possible? A Scottish chemist named A. J. Kearns-Smith from the University of Glasgow in 1985 is the author of such a theory. Based on similar assumptions by other scientists, he argued that organic particles, once between layers of clay and interacting with them, adopted a method of storing information and growing. Thus, the scientist considered the “clay gene” to be primary. Initially, the mineral and nascent life existed together, but at a certain stage they “scattered.”

The idea of ​​destruction (chaos) in the emerging world paved the way for the theory of catastrophism as one of the predecessors of the theory of evolution. Its proponents believe that the Earth has been affected by sudden, short-lived, violent events in the past, and the present is the key to the past. Each successive catastrophe destroyed existing life. The subsequent creation revived it already different from the previous one.

Materialistic doctrine

And here is another version regarding how life began on Earth. It was put forward by materialists. They believe that life emerged as a result of gradual chemical transformations extended over time and space, which, in all likelihood, occurred almost 3.8 billion years ago. This development is called molecular; it affects the area of ​​deoxyribonucleic and ribonucleic acids and proteins (proteins).

As a scientific movement, the doctrine arose in the 1960s, when active research was carried out affecting molecular and evolutionary biology, and population genetics. Scientists then tried to understand and confirm recent discoveries regarding nucleic acids and proteins.

One of the key themes that stimulated the development of this field of knowledge was the evolution of enzymatic function, the use of nucleic acid divergence as a “molecular clock”. Its disclosure contributed to a deeper study of the divergence (branching) of species.

Organic origin

Supporters of this doctrine talk about how life appeared on Earth as follows. The formation of species began a long time ago - more than 3.5 billion years ago (the number indicates the period in which life existed). Probably, at first there was a slow and gradual process of transformation, and then a rapid (within the Universe) stage of improvement began, a transition from one static state to another under the influence of existing conditions.

Evolution, known as biological or organic, is the process of change over time in one or more heritable traits found in populations of organisms. Hereditary traits are special distinctive characteristics, including anatomical, biochemical and behavioral, that are passed on from one generation to the next.

Evolution has led to diversity and diversification of all living organisms (diversification). Charles Darwin described our colorful world as “infinite forms, most beautiful and most wonderful.” One gets the impression that the origin of life is a story without beginning or end.

Special creation

According to this theory, all forms of life that exist today on planet Earth were created by God. Adam and Eve are the first man and woman created by the Almighty. Life on Earth began with them, believe Christians, Muslims and Jews. The three religions agreed that God created the universe in seven days, making the sixth day the culmination of his work: he created Adam from the dust of the earth and Eve from his rib.

On the seventh day God rested. Then he breathed in and sent him to tend the garden called Eden. In the center grew the Tree of Life and the Tree of the Knowledge of Good. God gave permission to eat the fruit of all the trees in the garden except the Tree of Knowledge (“for in the day that you eat of it you will die”).

But people disobeyed. The Koran says that Adam suggested trying the apple. God forgave the sinners and sent both of them to earth as his representatives. And yet... Where did life come from on Earth? As you can see, there is no clear answer. Although modern scientists are increasingly inclined to the abiogenic (inorganic) theory of the origin of all living things.