Trabajo De Fis

Timeline of evolution

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Visual representation of the history of life on Earth as a spiral

Life on Earth

view • discuss • edit

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Life

Photosynthesis

Eukaryotes

Complex multicellular life

Animals

Land plants

"Dinosaurs"

Mammals

Flowers

?

Formation

of Earth

?

Meteorite bombardment

?

Atmospheric oxygen

?

Ediacara biota

?

Cambrian explosion

?

Modern-looking

humans

Axis scale: millions of years ago.

Dates prior to 1 billion years ago are speculative.

Not to be confused with History of evolutionary thought.

This article is about the evolution of all life on Earth. See also the timeline of human evolution.

For more detailed and comprehensive coverage, see Evolutionary history of life.

This timeline of evolution of life outlines the major events in the development of life on planet Earth since it first originated until the present day. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules such as DNA and proteins. The similarities between all present day organisms indicate the presence of a common ancestor from which all known species, living and extinct, have diverged through the process of evolution.

The dates given in this article are estimates based on scientific evidence.

Contents

[hide]

* 1 Basic timeline

* 2 Detailed timeline

o 2.1 Hadean Eon

o 2.2 Archean Eon

o 2.3 Proterozoic Eon

o 2.4 Phanerozoic Eon

+ 2.4.1 Paleozoic Era

+ 2.4.2 Mesozoic Era

+ 2.4.3 Cenozoic Era

* 3 See also

* 4 Further reading

* 5 References

* 6 External links

[edit] Basic timeline

The basic timeline of a 4.5 billion year old Earth, with approximate dates:

* 3.8 billion years of simple cells (prokaryotes),

* 3 billion years of photosynthesis,

* 2 billion years of complex cells (eukaryotes),

* 1 billion years of multicellular life,

* 600 million years of simple animals,

* 570 million years of arthropods (ancestors of insects, arachnids and crustaceans),

* 550 million years of complex animals,

* 500 million years of fish and proto-amphibians,

* 475 million years of land plants,

* 400 million years of insects and seeds,

* 360 million years of amphibians,

* 300 million years of reptiles,

* 200 million years of mammals,

* 150 million years of birds,

* 130 million years of flowers,

* 65 million years since the non-avian dinosaurs died out,

* 2.5 million years since the appearance of the genus Homo,

* 200,000 years of anatomically modern humans,

* 25,000 years since the disappearance of Neanderthal traits from the fossil record.

* 13,000 years since the disappearance of Homo floresiensis from the fossil record.

[edit] Detailed timeline

Ma, ("megaannum") means "million years ago". ka means "thousand years ago" and ya means "years ago"

[edit] Hadean Eon

3800 Ma and earlier.

Date Event

4600 Ma The planet Earth forms from the accretion disc revolving around the young Sun.

4500 Ma According to the giant impact hypothesis the moon is formed when the planet Earth and the planet Theia collide, sending a very large number of moonlets into orbit around the young Earth which eventually coalesce to form the Moon.[1] The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions in which life formed.[2]

4100 Ma The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[3] PAH infall,[4] and iron sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing organic compounds.

4500-3500 Ma The earliest life appears, possibly derived from self-reproducing RNA molecules.[5][6] The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.[7][8][9]

3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteoroids. This constant disturbance may have obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal vents below the Earth's surface;[10] or life might have been transported to Earth by a meteoroid.[11]

3900-2500 Ma Cells resembling prokaryotes appear.[12] 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 and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.[13][14]

[edit] Archean Eon

3800 Ma – 2500 Ma

Date Event

3500 Ma Lifetime of the last universal ancestor;[15][16] the split between bacteria and archaea occurs.[17]

Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen.[18] 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.[19] The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rises, acting as a poison for many bacteria. The Moon is still very close to Earth and causes tides 1,000 feet (305 m) high. The Earth is continually wracked by hurricane-force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen catastrophe).

[edit] Proterozoic Eon

2500 Ma – 542 Ma

Date Event

2500 Ma Great Oxidation Event led by Cyanbacteria's oxygenic photosynthesis.[19]

2000 Ma Diversification and expansion of acritarchs. [20]

By 1850 Ma Eukaryotic cells appear. Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes engulfing each other via phagocytosis. (See Endosymbiosis). [21][22]

1400 Ma Great increase in stromatolite diversity.

By 1200 Ma Sexual reproduction first appears, increasing the rate of evolution.[23]

1200 Ma Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. First multicellular red algae evolve

1100 Ma Earliest dinoflagellates

1000 Ma First vaucherian algae (ex: Palaeovaucheria)

750 Ma First protozoa (ex: Melanocyrillium)

850–630 Ma A global glaciation may have occurred.[24][25] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.[26][27][28]

580–542 Ma The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.[29]

580–500 Ma Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.[30][31]

580–540 Ma The accumulation of atmospheric oxygen allows the formation of an ozone layer.[32] This blocks ultraviolet radiation, permitting the colonisation of the land.[32]

560 Ma Earliest fungi

550 Ma First fossil evidence for ctenophora (comb-jellies), porifera (sponges), and anthozoa (corals & anemones)

[edit] 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 and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.

[edit] Paleozoic Era

542 Ma – 251.0 Ma

Date Event

535 Ma Major diversification of living things in the oceans: chordates, arthropods (e.g. trilobites, crustaceans), echinoderms, mollusks, brachiopods, foraminifers and radiolarians, etc.

530 Ma The first known footprints on land date to 530 Ma, indicating that

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