Cenozoic era (Cenozoic). Cenozoic era: periods, climate

IN Paleogene The climate was warm and humid, as a result of which tropical and subtropical plants became widespread. Representatives of the marsupial subclass were widespread here.

The class of insects developed rapidly. Among them, highly organized species arose that promoted cross-pollination of flowering plants and fed on plant nectar. The number of reptiles has decreased. Birds and mammals lived on land and in the air; fish lived in the water, as well as mammals that re-adapted to life in the water. During the Neogene period, many genera of currently known birds appeared.

IN Quaternary period There was a repeated shift of the ice of the Arctic Ocean to the south and back, which was accompanied by cooling and the movement of many heat-loving plants to the south. With the retreat of the ice, they moved to their original places. This repeated migration (from lat. migratio - relocation) of plants led to mixing of populations, extinction of species not adapted to changed conditions, and contributed to the emergence of other, adapted species.

Human evolution

By the beginning of the Quaternary period, human evolution accelerates. Methods for making tools and their use are being significantly improved. People start cheating environment, learn to create for themselves favorable conditions. The increase in numbers and widespread distribution of people began to affect the flora and fauna. Hunting primitive people leads to a gradual reduction in the number of wild herbivores. The extermination of large herbivores led to a sharp decrease in the number cave lions, bears and other large predatory animals that feed on them. Trees were cut down and many forests were turned into pastures.

The time boundaries of the Cenozoic era are not difficult to determine: this is a period of geological time that begins with the Cretaceous-Paleogene extinction event, which destroyed the dinosaurs 66 million years ago and continues until the present day. Informally, the Cenozoic era is often referred to as the "Age of Mammals" because it was only after the dinosaurs became extinct that mammals were able to occupy the vacated ecological niches and become the dominant terrestrial life on the planet.

However, this characterization is somewhat unfair, since during the Cenozoic, not only mammals flourished, but also reptiles, birds, fish and even invertebrates!

Somewhat confusingly, the Cenozoic era is divided into various "periods" and "epochs", and scientists do not always use the same terminology when describing their research or discoveries. (This situation is in sharp contrast to the previous Mesozoic era, which is more or less neatly divided into , and periods.)

In the case of the Cenozoic era, the following main periods and eras are distinguished:

Paleogene period

(66-23 million years ago) was the time when mammals began their dominance. The Paleogene consists of three distinct eras:

Paleocene era

The Paleocene era, or Paleocene (66-56 million years ago) was quite calm from an evolutionary point of view.

During this time, the tiny surviving mammals got their first taste of their newfound freedom and began to cautiously explore new ecological niches. During the Paleocene era there were abundant big snakes, crocodiles and turtles.

Eocene epoch

The Eocene Epoch, or Eocene (56-34 million years ago) was the longest epoch of the Cenozoic era.

There was a huge abundance of mammal species in the Eocene; At this time, the first four-legged ungulates appeared on the planet, as well as the first recognizable primates.

Oligocene Epoch

The Oligocene Epoch, or Oligocene (34-23 million years ago), differs in climate change from the preceding Eocene, which opened up even more ecological niches for mammals. This was the era when some mammals (and even some birds) began to develop to gigantic sizes.

Neogene period

(23-2.6 million years ago) saw the continued evolution of mammals and other life forms, many of which were enormous. The Neogene consists of two eras:

Miocene era

The Miocene Epoch, or Miocene (23-5 million years ago) occupies the lion's share of the Neogene. Most mammals, birds and other animals began to acquire appearance, close to modern ones, although they were much larger.

Pliocene Epoch

The Pliocene Epoch, or Pliocene (5-2.6 million years ago), is often confused with the subsequent Pleistocene. This was a time when many mammals migrated (often across land bridges) into the areas they continue to inhabit today. Horses, primates, and other animal species continued to evolve.

Quaternary period

(2.6 million years ago - to the present) is still the shortest of all geological periods of the Earth. The Anthropocene consists of two even shorter epochs:

Pleistocene era

The Pleistocene era, or Pleistocene (2.6 million - 12 thousand years ago) is characterized by large mammals megafauna such as the woolly and , which became extinct at the end of the last ice age (due in part to climate change and predation by the earliest humans).

Holocene era

The Holocene Epoch, or Holocene (12,000 years ago - up to the present) represents almost the entire modern history humanity. Unfortunately, this is also an era when many mammals and other life forms became extinct due to environmental changes caused by negative anthropogenic impacts from human activities.

The Quaternary period began 2.6 million years ago and continues to the present day. It is one of three periods (66 million years ago - to the present) and follows (23-2.6 million years ago). The Anthropocene is divided into two eras:

• Pleistocene era, or Pleistocene (2.6 million - 11.7 thousand years ago);
• Holocene epoch, or Holocene (11.7 thousand years ago - to the present).

Geography

Major geographical changes that occurred during this time period included the formation of the Bosporus and Skagerrak straits during the glacial periods, which respectively turned the Black and Baltic Sea in, and then their flooding (and the return of salt water) by rising sea levels; periodic flooding of the English Channel, the creation of a land bridge between Great Britain and the European part of the world; the periodic appearance of the land-based Bering Isthmus, forming a bridge between Asia and North America; and periodic flash flooding of the American northwest with glacial water.

Current extent of Hudson Bay, Great Lakes, and other large lakes North America is a consequence of the restructuring of the Canadian Shield since the last ice age; During the Quaternary period, coastlines constantly changed.

Climate

Throughout the Quaternary period, the planet revolved around the Sun. Small shifts caused ice ages. Around 800,000 years ago, a cyclical pattern emerged: an ice age lasted about 100,000 years, followed by warmer interglacials of 10,000 to 15,000 years each. The last ice age ended about 10 thousand years ago. Sea levels rose rapidly and the continents reached their current shape.

As temperatures cooled, glacial plates spread from the poles and covered much of North America and Europe, parts of Asia and South America, and all of Antarctica. With so much water locked in glaciers, sea levels are falling.

Animal world

Birds

IN quaternary period Birds continued to evolve throughout the world and inhabit a variety of habitats. However, many giant flightless birds have gone extinct, including the dodo, or Mauritian dodo. Large flying birds have also disappeared, including Teratornis merriam, which had a wingspan of more than 3.5 m and a weight of about 15 kg.

Reptiles and amphibians

Extinct reptiles, lizards and turtles were larger than extant ones, and crocodiles were smaller, although snakes did not tend to have a particular body size.

Body size played a complex role in the extinction of late Quaternary reptiles. Larger species of lizards and turtles have been clearly affected by extinction mechanisms such as overexploitation and introduction invasive species, which led to the predominance of large animals among extinct taxa.

Marine fauna

From the very beginning of the Quaternary period, whales and sharks dominated the seas, and were at the top, above the otters, seals, dugongs, fish, squid, urchins and microscopic plankton that filled the lower trophic level.

Human

In fact, the Quaternary is often considered the "era of men." Homo erectus ( Homo erectus) appeared in Africa early in this period, and developed larger brains and larger high intelligence. The first modern humans evolved in Africa about 190 thousand years ago and dispersed to Europe and Asia, and then to Australia and America. Our species has greatly changed the land and sea ​​life, and now, according to scientists, humanity is causing global changes climate.

Flora

Despite significant climatic differences between the Pleistocene and Holocene epochs, much of it remained unchanged. The Pleistocene era had two main climatic conditions: glacial and interglacial. During the Ice Age, most of the land was covered with ice, and the vegetation was mainly tundra, which included mosses, sedges, shrubs, lichens and low-growing grasses; however, during the interglacial period, or a time when most of the soil was not covered by ice, forested areas existed and coniferous forests. The emergence occurred during the beginning of the Holocene. This habitat allowed many animals and plants to flourish. During this period, conifers and deciduous forests, as well as savannas where herbivores grazed and flourished.

Currently, the Cenozoic era continues on Earth. This stage of the development of our planet is relatively short when compared with previous ones, for example, the Proterozoic or Archean. So far it is only 65.5 million years old.

Geological processes that occurred throughout the Cenozoic shaped modern look oceans and continents. The climate and, as a consequence, the flora in one or another part of the planet gradually changed. The previous era - the Mesozoic - ended with the so-called Cretaceous catastrophe, which led to the extinction of many animal species. The beginning of a new era was marked by the fact that empty ecological niches began to be filled again. The development of life in the Cenozoic era occurred rapidly both on land and in water and in the air. Mammals occupied a dominant position. Finally, human ancestors appeared. People turned out to be very “promising” creatures: despite repeated climate changes, they not only survived, but also evolved, settling throughout the planet. Over time human activity became another factor in the transformation of the Earth.

Cenozoic era: periods

Previously, the Cenozoic (“era of new life”) was usually divided into two main periods: Tertiary and Quaternary. Now another classification is in use. The very first stage of the Cenozoic is the Paleogene (“ ancient education"). It began approximately 65.5 million years ago and lasted 42 million years. The Paleogene is divided into three subperiods (Paleocene, Eocene and Oligocene).

The next stage is Neogene (“new formation”). This era began 23 million years ago, and its duration was approximately 21 million years. The Neogene period is divided into Miocene and Pliocene. It is important to note that the emergence of human ancestors dates back to the end of the Pliocene (though at that time they did not even resemble modern people). Somewhere 2-1.8 million years ago, the Anthropocene, or Quaternary, period began. It continues to this day. Throughout the Anthropocene, human development has occurred (and continues to occur). The subperiods of this stage are the Pleistocene (glacial era) and Holocene (post-glacial era).

Climatic conditions of the Paleogene

The long period of the Paleogene opens the Cenozoic era. The climate of the Paleocene and Eocene was mild. Near the equator average temperature reached 28 °C. In the area North Sea the temperature was not much lower (22-26 °C).

On the territory of Spitsbergen and Greenland, evidence was found that plants characteristic of modern subtropics felt quite comfortable there. Traces of subtropical vegetation have also been found in Antarctica. There were no glaciers or icebergs in the Eocene. There were areas on Earth that did not lack moisture, regions with variable humid climate and dry areas.

During the Oligocene period it became sharply colder. At the poles, the average temperature dropped to 5 °C. The formation of glaciers began, which later formed the Antarctic Ice Sheet.

Paleogene flora

The Cenozoic era is a time of widespread dominance of angiosperms and gymnosperms (conifers). The latter grew only in high latitudes. At the equator they prevailed rain forests, the basis of which were palms, ficuses and various representatives sandalwood The further from the sea, the drier the climate became: savannas and woodlands spread in the depths of the continents.

In the middle latitudes, moisture-loving tropical plants were widespread temperate climate(tree ferns, breadfruit ferns, sandalwood, banana trees). Closer to high latitudes species composition became completely different. These places are characterized by typical subtropical flora: myrtle, chestnut, laurel, cypress, oak, thuja, sequoia, araucaria. Plant life in the Cenozoic era (in particular, during the Paleogene era) flourished even beyond the Arctic Circle: in the Arctic, Northern Europe and America, a predominance of coniferous-broad-leaved deciduous forests is noted. But we met here and subtropical plants listed above. The polar night was not an obstacle to their growth and development.

Paleogene fauna

The Cenozoic era provided the fauna with a unique chance. Animal world changed dramatically: dinosaurs were replaced by primitive ones small mammals, living mainly in forests and swamps. There are fewer reptiles and amphibians. Various proboscis animals predominated, indicotheriums (similar to rhinoceroses), tapiro- and pig-like animals.

As a rule, many of them were adapted to spend part of their time in water. During the Paleogene period, the ancestors of horses also appeared, various rodents, later - predators (creodonts). Toothless birds nest on the treetops, and predatory diatrymas live in the savannas - birds that cannot fly.

Great variety of insects. As for the marine fauna, cephalopods and bivalves, corals; Primitive crayfish and cetaceans appear. The ocean at this time belongs to bony fish.

Neogene climate

The Cenozoic era continues. The climate during the Neogene era remains relatively warm and quite humid. But the cooling that began in the Oligocene makes its own adjustments: glaciers no longer melt, humidity drops, and the climate becomes more continental. By the end of the Neogene, zonation approached modern (the same can be said about the outlines of oceans and continents, as well as about the relief earth's surface). The Pliocene marked the beginning of another cold snap.

Neogene, Cenozoic era: plants

At the equator and tropical zones either savannas or rain forests. Temperate and high latitudes could boast the greatest diversity of flora: here they were widespread broadleaf forests, mostly evergreen. As the air became drier, new species appeared, from which the modern flora of the Mediterranean gradually developed (olives, plane trees, walnut, boxwood, southern pine and cedar). In the north, evergreens no longer survived. But coniferous-deciduous forests demonstrated a wealth of species - from sequoia to chestnut. At the end of the Neogene, landscape forms such as taiga, tundra and forest-steppe appeared. This again was due to the colder weather. North America and Northern Eurasia became taiga regions. IN temperate latitudes With arid climate steppes were formed. Where there used to be savannas, semi-deserts and deserts arose.

Neogene fauna

It would seem that the Cenozoic era is not so long (in comparison with others): the flora and fauna, however, managed to change greatly since the beginning of the Paleogene. Placentals became the dominant mammals. First, the anchytherium fauna developed, and then the hipparion fauna. Both are named after characteristic representatives. Anchytherium is the ancestor of the horse, a small animal with three toes on each limb. Hipparion is, in fact, a horse, but also three-toed. One should not think that the indicated fauna included only relatives of horses and simply ungulates (deer, giraffes, camels, pigs). In fact, among their representatives there were predators (hyenas, lions), and rodents, and even ostriches: life in the Cenozoic era was distinguished by fantastic diversity.

The spread of the mentioned animals was facilitated by an increase in the area of ​​savannas and steppes.

At the end of the Neogene, human ancestors appeared in the forests.

Anthropocene climate

This period is characterized by alternating glaciations and warming periods. When the glaciers advanced, their lower boundaries reached 40 degrees northern latitude. The largest glaciers of that time were concentrated in Scandinavia, the Alps, North America, Eastern Siberia, in the Subpolar and Northern Urals.

In parallel with the glaciations, the sea advanced onto the land, although not as powerful as in the Paleogene. The interglacial periods were characterized by a mild climate and regression (drying of the seas). Now the next interglacial period is underway, which should end no later than in 1000 years. After it, another glaciation will occur, which will last about 20 thousand years. But it is unknown whether this will actually happen, since human intervention in natural processes has provoked climate warming. It's time to think about whether the Cenozoic era will end in a global environmental catastrophe?

Flora and fauna of the anthropogene

The advance of glaciers forced heat-loving plants to move south. True, mountain ranges prevented this. As a result, many species have not survived to this day. During the glaciations, there were three main types of landscapes: taiga, tundra and forest-steppe with their characteristic plants. Tropical and subtropical zones greatly narrowed and shifted, but still remained. During interglacial periods, broad-leaved forests predominated on Earth.

As for the fauna, the primacy still belonged (and belongs) to mammals. Massive, furry animals (mammoths, woolly rhinoceroses, megaloceros) became business card ice ages. Along with them there were bears, wolves, deer, and lynxes. All animals were forced to migrate as a result of cold and warm temperatures. The primitive and unadapted died out.

Primates also continued their development. The improvement of the hunting skills of human ancestors can explain the extinction of a number of game animals: giant sloths, North American horses, mammoths.

Results

It is unknown when the Cenozoic era will end, the periods of which we discussed above. Sixty-five million years is quite a bit by the standards of the Universe. However, during this time continents, oceans and mountain ranges managed to form. Many species of plants and animals became extinct or evolved under the pressure of circumstances. Mammals took the place of dinosaurs. And the most promising of mammals turned out to be man, and last period The Cenozoic - Anthropocene - is associated mainly with human activity. It is possible that it depends on us how and when the Cenozoic era - the most dynamic and shortest of earthly eras - will end.