Information about Evolutionary Timeline

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For the history of evolutionary biology, see History of evolutionary thought.
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth. For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.

In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. Contemporary species are related to each other through common descent, products of evolution and speciation over billions of years.

Basic timeline

The basic timeline is a 4.6 billion year old Earth, with (very approximately):

Detailed timeline

Note that Ma means "million years ago".

Hadean eon

3800 Ma and earlier.

Date Event
4567.17 MaThe planet Earth forms from the accretion disc revolving around the young Sun.
4533 MaThe planet Earth and the planet Theia collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the Moon. The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions for the formation of life.[1]
4100 MaThe surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[2]
Between 4500 and 2500 MaThe earliest life appears, possibly derived from self-reproducing RNA molecules. The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition. Natural selection favours those molecules which are more efficient at replication. DNA molecules then take over as the main replicators. They soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.
3900 MaLate Heavy Bombardment: peak rate of impact events upon the inner planets by meteors. This constant disturbance probably obliterated any life that had already evolved, as the oceans boiled away completely; conversely, life may have been transported to Earth by a meteor. [3]
Somewhere between 3900 - 2500 MaCells resembling prokaryotes appear. These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose. Glycolysis generates ATP molecules as short-term energy currency, and ATP continue to be used in almost all organisms, unchanged, to this day.

Archean eon

3800 Ma - 2500 Ma

Date Event
3500 MaLifetime of the last universal ancestor; the split between the bacteria and the archaea occurs.

Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen. These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.
3000 Ma Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The moon is still very close to the earth and causes tides 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen Catastrophe)

Proterozoic eon

2500 Ma - 542 Ma

Date Event
By 2100 MaEukaryotic cells appear. Eukaryotes contain membrane-bound organelles with diverse functions, probably derived prokaryotes englufing each other via phagocytosis.
By 1200 MaSexual reproduction evolves, increasing the rate of evolution.[4]
1200 MaSimple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity.
850–630 MaA global glaciation may have reduced the diversity of life. Opinion is divided on whether it increased or decreased the rate of evolution.
580-542 MaThe Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.
580–500 MaMost modern groups begin to appear in the fossil record during the Cambrian explosion.
Around 540 MaThe accumulation of atmospheric oxygen allows the formation of an ozone layer. This blocks ultraviolet radiation, permitting the colonisation of the land.

Phanerozoic eon

542 Ma - present

The Phanerozoic eon, literally the "period of well-displayed life", marks the appearance in the fossil record of abundant, shell-forming organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.

Paleozoic era

542 Ma - 251.0 Ma

Date Event
530 MaThe first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.[5]
475 MaThe first primitive plants move onto land,[6] having evolved from green algae living along the edges of lakes.[7] They are accompanied by fungi, which may have aided the colonisation of land through symbiosis.
363 MaBy the start of the Carboniferous period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies; sharks predated the oceans,[8] and vegetation covered the land, with seed-bearing plants and forests soon to flourish. Four-limbed tetrapods gradually gain adaptions which will help them occupy a terrestrial life-habit.
251.4MaThe Permian-Triassic extinction event eliminates over 95% of species. This "clearing of the slate" may have led to an ensuing diversification.

Mesozoic era

Date Event
From 251.4 MaThe Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
220 Ma
Enlarge picture
Eoraptor, an early dinosaur.
Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.
200 MaThe first accepted evidence for viruses - the group Geminiviridae at least exists.[9] Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon.
130 MaThe rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This innovation causes a major burst of animal evolution through co-evolution.

Cenozoic era

65.5 Ma - present

Date Event
65.5 Ma
Enlarge picture
An asteroid impact probably wiped out half of all animals species 65½ million years ago. Other life forms became extinct as well.
The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including all non-avian dinosaurs.
35 MaGrasses evolve from among the angiosperms; grassland dominates many terrestrial ecosystems.
14,000 years agoThe term Anthropocene has been used to describe the period of time during which Man has had a major impact on the planet and its inhabitants. Its beginning is marked by the megafaunal extinction in the Americas which signify the onset of the Holocene extinction event. Fierce debate rages about the influence of man in the initiation of this extinction, but no-one can deny that humanity is contributing to its propagation.
Present dayWith a human population approaching 6.6 billion,[10] the impact of humanity is felt in all corners of the globe. Overfishing, anthropogenic climate change, industrialisation, intensive agriculture, clearance of rain forests and other activities contribute to a dramatically rising extinction rate.[11] At current rates, humanity will have eradicated one-half of life's biodiveristy over the next hundred years.[12]

See also

Further reading

References

1. ^ Planetary Science Institute page on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.
2. ^ "However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development." How the Oceans Formed (URL accessed on January 9, 2005)
3. ^ " Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across" Geophysicist Sleep: Martian underground may have harbored early life (URL accessed on January 9, 2005)
4. ^ "'Experiments with sex have been very hard to conduct,' Goddard said. 'In an experiment, one needs to hold all else constant, apart from the aspect of interest. This means that no higher organisms can be used, since they have to have sex to reproduce and therefore provide no asexual control.'
Goddard and colleagues instead turned to a single-celled organism, yeast, to test the idea that sex allows populations to adapt to new conditions more rapidly than asexual populations." Sex Speeds Up Evolution, Study Finds (URL accessed on January 9, 2005)
5. ^ "The oldest fossils of footprints ever found on land hint that animals may have beaten plants out of the primordial seas. Lobster-sized, centipede-like or slug like animals such as Protichnites and Climactichnites made the prints wading out of the ocean and scuttling over sand dunes about 530 million years ago. Previous fossils indicated that animals didn't take this step until 40 million years later." Oldest fossil footprints on land
6. ^ "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450-440 m.y.a.) on the basis of fossil spores" Transition of plants to land
7. ^ "The land plants evolved from the algae, more specifically green algae, as suggested by certain common biochemical traits" The first land plants
8. ^ "The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. Introduction to shark evolution, geologic time and age determination
9. ^ "Viruses of nearly all the major classes of organisms—animals, plants, fungi and bacteria/archaea—probably evolved with their hosts in the seas, given that most of the evolution of life on this planet has occurred there. This means that viruses also probably emerged from the waters with their different hosts, during the successive waves of colonisation of the terrestrial environment." Origins of Viruses (URL accessed on January 9, 2005)
10. ^ An United States Census Bureau estimate of the number of people alive on Earth at any given moment. United States census bureau
11. ^ The American Museum of Natural History National Survey Reveals Biodiversity Crisis (URL accessed on February 23, 2006)
12. ^ E. O. Wilson, Harvard University, The Future of Life (2002)

External links

Evolutionary thought has roots in antiquity as philosophical ideas known to the Greeks, Romans, Indians, Chinese and Muslims. Until the 18th century, however, Western biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time.
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Life (Biota)

Domains and Kingdoms
  • Life on Earth (Gaeabionta)
  • Nanobes

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EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
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history of Earth covers approximately 4.6 billion years (4,567,000,000 years), from Earth’s formation out of the solar nebula to the present. This article presents a broad overview, summarizing the leading, most current scientific theories.
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The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of Earth.
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Biology (from Greek: βίος, bio, "life"; and λόγος, logos, "knowledge"), also referred to as the biological sciences, is the scientific study of life.
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character is an attribute of an organism that allows it to be compared with another. In genetics this refers to heritable features which can exist in more than one state.[1] A trait
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Speciation is the evolutionary process by which new biological species arise. There are four modes of natural speciation, based on the extent to which speciating populations are geographically isolated from one another:
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A group of organisms is said to have common descent if they have a common ancestor. In modern biology, it is generally accepted that all living organisms on Earth are descended from a common ancestor or ancestral gene pool.
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Speciation is the evolutionary process by which new biological species arise. There are four modes of natural speciation, based on the extent to which speciating populations are geographically isolated from one another:
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age of the Earth to be around 4.54 billion years (4.54109 years).[1] This age represents a compromise between the interpretations of oldest-known terrestrial minerals – small crystals of zircon from the Jack Hills of Western Australia – and
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Prokaryotes (IPA: /prəʊˈkæriəʊtiz/) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles.
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The first organisms that existed were unicellular. How organisms then became multicellular is a huge evolutionary step and is consequently under much debate.

Hypotheses on origins of multicellularity


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Arthropoda
Latreille, 1829

Subphyla and Classes
  • Subphylum Trilobitomorpha
  • Trilobita - trilobites (extinct)
  • Subphylum Chelicerata

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Embryophyta

Divisions
  • Non-vascular land plants (bryophytes)
  • Marchantiophyta - liverworts
  • Anthocerotophyta - hornworts

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Insecta
Linnaeus, 1758

Orders
Subclass Apterygota
* Archaeognatha (bristletails)
* Thysanura (silverfish)
Subclass Pterygota
* Infraclass Paleoptera (Probably paraphyletic)

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For other meanings of seed, see seed (disambiguation).


SEED

General
KISA
1998

Cipher detail
Key size(s):| 128 bits

Block size(s):| 128 bits
Nested Feistel network
16

SEED
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Amphibia
Linnaeus, 1758

Subclasses and Orders

   Order Temnospondyli - extinct
Subclass Lepospondyli - extinct
Subclass Lissamphibia
   Order Anura
   Order Caudata
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Sauropsida*
Goodrich, 1916

Subclasses
  • Anapsida
  • Diapsida
Synonyms
  • Reptilia Laurenti, 1768
Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Aves
Linnaeus, 1758

Orders

About two dozen - see section below

Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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Dinosauria *
Owen, 1842

Orders & Suborders
  • Ornithischia
  • Cerapoda
  • Thyreophora
  • Saurischia

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Homo
Linnaeus, 1758

Species

Homo sapiens
See text for extinct species.
Homo is the genus that includes modern humans and their close relatives. The genus is estimated to be between 1.5 and 2.5 million years old.
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Hadean (IPA: /ˈheɪdiən/) is the geologic eon before the Archean. It started at Earth's formation about 4.6 billion years ago (4600 Ma), and ended roughly 3.
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