The Evolutionary History of the Earth
Last updated: Dec 08, 2008
site is intended to give a one-page summary of the history of the
Earth from its origin 4.6 billion years ago to its demise
from an expanding sun in about five billion years. The focus
interrelationship between evolution, continental configuration due to
plate tectonics, and climate.
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line between periods in the
Paleozoic and Mesozoic eras
major mass extinction. The following icons are used:
Map of how the Earth's continents were configured at that time, from PALEOMAP Project.
Map from Paleogeographic Atlas Project, from the University of Chicago. (These PDF images may be slow to load)
Paleomaps presented by Ron Blakey, Northern Arizona University.
Link to a paleoclimate graph showing temperature trends for the time period.
A major period of flood basalt eruptions, with at least a million cubic kilometers of lava produced.
A major meteorite impact, with a crater diameter greater than 100 km. For more details, see below.
T This column represents the Earth's temperature, with dark blue representing an ice age.
O2 This column represents the percentage of oxygen. Darker blue means higher oxygen levels. See below.
|Hadean era (origin of Earth/Moon system)||0||4600-4000|
|Archean era (first life: anaerobic bacteria)||0||4000-2500|
|PaleoProterozoic era (aerobic bacteria, oxygenation of atmosphere)||5?||2500-1600|
|MesoProterozoic era (first Eukaryotic cells)||9?||1600-805
||Sturtian period (first "snowball earth" event)||16||805-605
(soft-bodied multicellular animals)
(First animal and plant life)
|Cambrian period (marine animals with hard body parts and eyes)||18||543-490|
|Ordovician period (first jawless fish, algae)||16||490-443|
|Silurian period (fish with jaws, insects, land plants)||20||443-417|
|Devonian period (armored fish, large forests)||25||417-354|
|Carboniferous period (amphibians, forests and swamps)||30||354-290|
|Permian period (origin of mammals and reptiles) (?)||20||290-252|
(Age of Reptiles)
|Triassic period (amphibians, reptiles, conifers)||15||252-200|
|Jurassic period (dinosaurs, first birds)||13||200-135|
|Cretaceous period (flowering plants, dinosaurs)||18||135-65|
(Age of Mammals)
|Tertiary period||Paleocene epoch (grass, mammal diversification)||17||65-55|
|Eocene epoch (angiosperm herbs, trees with fruit)||18||55-38|
|Oligocene epoch (elephants, horses)||19||38-26|
|Miocene epoch (kelp forests, grasslands)||20||23-6|
|Pliocene epoch (diversification of apes and hominids)||21||6-1.8|
|Quaternary period||Pleistocene epoch (ice ages, human ancestors)||21||1.8-0.01|
|Holocene epoch (agriculture, civilisation)||21||0.01-0|
second half of the
Age of Animals 50:
|Cenoproterozoic (plants, animals, eukaryotes disappear)||500-1000
is again only fit for bacteria)
expands to reach Earth's orbit, life can no longer exist)
system is formed from the debris of several supernova explosions.
from the solar system nebula.
about the size of Mars collides
Earth. Most of the crust is ejected into space, congealing
reduced amount of crust on Earth results in thin crustal plates that
can subduct (slide) under each other, making plate tectonics
possible. This body may have formed
at Lagrange points (details)
on the Earth's orbit.
volatiles from the mantle to the atmosphere. Abundant impact
mineral crystals. Possible existence of first continents.
Era - The First Life (Anaerobic
crust formation and start of tectonic activity.
origin of the
first anaerobic eubacteria. According to Carl Woese [ref],
archaebacteria originate at the same time.
known sedimentary rocks in Isua, Greenland, with banded iron formations
and isotopic evidence for life. However, this interpretation
of banded iron formations. Iron dissolved in the ocean was
oxidized and precipitated, probably by bacteria. The oxygen
itself was produced by photosynthetic bacteria. This process
continued for nearly two billion years, and is the source of all iron
mined today. There is 20 times more oxygen in tied up in
iron formations than in the present atmosphere.
stromatolites in the Apex chert of northwest Australia, actually dated
to within 10 million years. These microbial mats imply
photosynthetic bacterial communities. Given the existence of
banded iron formations, the bacteria were probably cyanobacteria.
continents formed from raised portion of plates known as the
oxygenation of the atmosphere
|2500||Peak of banded iron formations. Oxygen production reaches the point where it is no longer all absorbed by elements such as iron. It begins to enter the atmosphere and steadily works to strengthen the ozone layer and change the Earth's chemically reducing atmosphere into a chemically oxidizing one.|
glaciation event (an early Snowball Earth), possibly caused by
drawing down the carbon dioxide supply.
appearance of Grypania, spiral fossils several cm long. The
eukaryotes, or cyanobacterial colonies.
banded iron formations by red beds (oxidized iron
sediments), indicating worldwide oxygen atmosphere of about 3%,
compared to 20% today..
Acritarchs. These are interpreted as the first eukaroyotes,
may simply be large cyanobacteria.
terrestrial cyanobacteria (desert crust)
||Bangiomorpha pubescens, from the Hunting Formation, arctic Canada, is the earliest taxonomically resolved eukaryote on record. More importantly, it is the earliest known example of both sexual reproduction and complex multicellularity.|
||A rapid diversification of planktonic eukaryote assemblages begins, followed by a decline in both abundance and diversity, between 900 and 675 Ma.|
||Seilacher et al. (1998, p81) reports trace fossils from the one billion year old Chorhat Sandstone formation in the Son Valley, central India, which the authors interpret as the burrows of triploblastic undermat miners - infaunal animals that excavated tunnels underneath microbial mats “which served as a food source as well as an oxygen mask for the worm like animals that were exploiting its decaying base”.|
Era - Multicellular life
Rhodinia splits apart,
creating more coastline with continental shelves hospitable to
plankton. Photosynthesis removes
carbon dioxide from air, reducing greenhouse effect and cooling the
Sturtian Ice Ages. (Snowball
One view has it that the entire ocean froze to a depth of 1.5 km at the
equator and 3 km at the poles, with an average world wide temperature
C. These ice ages last millions of years, until the buildup
dioxide from volcanoes heats the atmosphere enough to melt the ice,
to average temperatures of +40o
C. The alternative
Earth hypothesis suggests these ice ages were less severe.
|630||Varanger or Marinoan glaciation. The second "Snowball Earth" event.|
|580||Gaskiers Glaciation. The iron content of deep-sea sediments shows that the deep ocean was anoxic (no oxygen) and ferruginous (iron rich) before and during the Gaskiers glaciation 580 million years ago and that it became oxygenated afterward. The first known members of the Ediacara biota (soft-bodied multi-cellular animals) arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later. [Science Sep 07]|
||A meteor similar in
size as the one at the K/T
boundary hits Australia to form the Acraman crater. An
biological complexity follows immediately after, possible stimulated by
recovery from mass extinction of plankton.
Era - The first plant and animal
|543||The "Cambrian Explosion" results in the rapid evolution of animals with hard body parts. These are easily fossilized, giving the impression that life suddenly appeared. Their Precambrian ancestors were much smaller, and not easily preserved as fossils. The "explosion" may be more a rapid increase in size rather than change in structure. Hard body parts such as shells evolved to support the the larger size of the organisms. The segmented shape of many arthropods increases the surface area available for respiration, and may be an adaptation to the low oxygen levels at the time.|
have a cartilaginous rather than a bony skeleton and lacked jaws,
simply having a hole for a mouth. But they have four "limbs"
(paired fins) used for propulsion and navigation in the
water. These fish tended to have thick bony plates as armor.
earliest evidence for
terrestrial activity by animals, provided by trace
fossils, are tracks made by
multiple ~50 cm-sized, many legged
animals preserved in an eolian sandstone in the Nepean Formation
(Potsdam Group) near Kingston, Ontario. These track-makers were
probably amphibious arthropods. This seems to precede the
existence of plants on land.
||Cambrian period ends with a mass extinction, probably caused by an ice age. This involved the loss of 75% of the trilobite families, half the sponge families, and many brachiopods and snails. Ordovician period begins.|
|465||The Great Ordovician Diversification Event: Life's largest burst of evolutionary variety involving marine organisms such as the brachiopods, shellfish living on the sea floor. This event, which took place over 20 million years, coincides with a large increase in meteor impacts caused by an asteroid collision. The exact connection between meteor impact and this diversivication is not yet known. [Science: Dec 21, 2007]|
of spores and banded tubes indicate the first presence of land plants
(Bryophytes) in the late Ordovician. These plants evolved
||Ordovician period ends with the second most severe mass extinction, accompanied by a glaciation. One [crazy] theory claims it was caused by a nearby gamma ray burst. This would destroy the ozone layer, and shroud the earth with nitrous oxide smog. The sun's ultraviolet radiation would kill life near the surface, and the smog would trigger the observed ice age, causing further extinction.|
|430||During the Silurian period, organisms such as liverworts, lichens, fungi and mosslike plants inhabited humid nearshore habitats. The first land animals were scorpions. By the end of the period, the evolution of true vascular plants, with water conducting tissues and pores for gas exchange, had begun.|
period begins with oxygen levels one half present day levels, and ten
times the carbon dioxide. The
land animals, primitive wingless insects, appear. There were
major continents, Laurussia in the north and Gondwana in the south,
gradually approaching each other, closing the Iapetus Ocean between
half of the Devonian, oxygen levels were rising. Primitive plants
diversified into four major
lineages: the seedless Lycopods,
plus the seed-bearing Gymnosperms. The Devonian is known as
Age of Fishes, and all major groups of fish were present. Aided by the
high oxygen levels, a second wave of animals began to colonize the land.
first amphibians move onto
land. Evolving from fish, their fins develop into
legs. They still must return to the water to lay their eggs.
||Devonian period ends with a sequence of mass extinctions, possibly caused by newly evolved plants drawing down carbon dioxide triggering an ice age. Oxygen in the atmosphere had reached near present levels.|
gymnosperms (coniferous trees) in the Carboniferous period, which are
distinguished by their seeds. This is a
more effective means of reproduction, as the seeds can survive in a dry
environment. These softwood trees are still with us today. As forests
were converted to coal, carbon dioxide levels fell
today's levels, and oxygen levels rose to above 30% (compared to 21%
today). This encouraged the development of flying insects,
of which had wingspans of up to three feet.
|320||The first (Anapsid) reptiles evolved from amphibians, distinguished by their eggs that could be laid and hatched outside of water. Like gymnosperm seeds, these may be an adaptation to a drier environment.|
Permian period sees the original Anapsid reptiles diverge into the
Synapsids and Dyapsids. The Synapsids gave rise to the Therapsids, also
known as mammal-like reptiles, the ancestors of
today's mammals. By the late Permian these animals were the first to
achieve endothermy (warm-bloodedness). The Dyapsids are the ancestors
as snakes and Dinosaurs.
|285||Origin of the order Coleoptera, or beetles, which now represent one fourth of all names species. [Science: Dec 21 2007]|
|252||Permian period ends with the greatest mass extinction ever, killing 90-95% of both land and sea species [BEN1]. This was accompanied by rapidly falling oxygen levels. Multiple causes include the formation of the super-continent Pangea, glaciation at the poles, and massive flood basalt eruptions in Siberia. Anoxic oceans released large amounts of toxic hygrogen sulfide. Much less likely causes: a meteor impact (Bedout, north of Australia), and even clumps of dark matter.|
era - The Age of Reptiles
Triassic period begins with
the devastated ecosystem left by the Permian extinction. On
a single species, Lystrosaurus
(a 1 meter long
pig-like herbivore) represents 95% of large animal life.
dinosaurs appear. They are small, but being bipedal gives
speed advantage. The warm climate of the Mesozoic era gives
cold-blooded reptiles a relative advantage over warm-blooded mammals.
Their efficient respirotory system is well adapted to the low oxygen
levels at the time.
era ends with a mass extinction of about 70% of all species. The
extinction on land began about 700,000 years before the extinction in
the ocean. This was accompanied by a rise in carbon dioxide
levels and massive
second generation of dinosaurs appear in the Jurassic. Mostly
herbivores, they included the largest dinosaurs of all time.
There was also a significant
flood basalt eruption.
possibly the ancestor of modern birds, was a feathered dinosaur capable
flowering plants (angiosperms). These evolved to become
dominant vegetation, including all grasses,
hardwood trees, all crops, etc.
|93||During the Cenomanian-Turonian mass extinction the entire ocean became statified and stagnant. The deep ocean became anoxic and all life in it died. This date has also been identified as the origin of the common ancestor of the grasses that exist today [Science Nov 2008].|
|80||The most prominent plant-eating dinosaurs were digesting different varieties of grass between 65 million and 71 million years ago, But grasses must have originated considerably earlier, well over 80 million years ago, for such a wide variety to have evolved and spread to the Indian subcontinent.|
|75||The third generation of dinosaurs reaches its peak in the Cretaceous, then starts to slowly decline. These include most of the dinosaurs featured in "Jurassic" Park. The climate of the Cretaceous was very warm, with large portions of the continents flooded by sea levels up to 100m (330 feet) above today's levels. Carbon dioxide levels were four to eight times higher than today. Average temperatures were about the same everywhere on Earth (about 10° C higher than today), from the poles to the equator. Dinosaurs and semi-tropical vegetation are known from within 10° of the Cretaceous poles.|
||The climate cools and the extinction rate of dinosaurs increases. Around 66 Mya massive flood basalts occurred in the Deccan Traps in India, releasing as much energy as the large Chicxulub Meteorite 65 Mya. A recent theory has it that the heat of re-entry of impact ejecta killed all land animals not burrowed into the earth. There were a lot of extinctions at sea, including the ammonites. Both events triggered the release of carbon dioxide, leading to global warming in the early Paleocene.|
- The Age of Mammals
|60||In the Paleocene, birds began to diversify and occupy new niches. Also, the first appearance of modern pines, cacti and palms. Also, a flood basalt event.|
fossil evidence of dry land
grass. Fossil pollen has been found
in South America and Africa. Although it may appear to be
primitive, grass is an
evolutionary latecomer, arising in the late Cretaceous.
|55||Paleocene-Eocene Thermal Maximum. An episode of rapid and intense warming (up to 7°C at high latitudes) which lasted less than 100,000 years. This occurred at the same time as a flood basalt eruptionthat occurred when the North Atlantic ocean opened over the ancestral Iceland hot spot. The temperature rise was caused by greenhouse gas release during magma interaction with basin-filling carbon-rich sedimentary rocks. A combination of ocean acidification from rapidly rising carbon dioxide levels, and ocean anoxia from reduced circulation led to a mass extinction of deep ocean life. Other theories claim the warming was caused by the release of methane hydrates, or it was triggered by comet impact.|
|50||Warm global climate in the Eocene. Subtropical rainforests with very broad leaves at the poles. Primitive monkeys have evolved. Appearance of the first whales and horses (Eohippus). Around this time the continent of India began to collide with Asia, causing the rise of the Himalaya Mountains and the Tibetan Plateau. This led to a change in weather patterns and an increase of removal of carbon dioxide via weathering, which may have caused the climate to begin to cool [Science Aug 2008].|
meteorite impacts create 100 km craters at Chesapeake (USA)
(Siberia), but there is no
linked extinctions. Antarctica separates from South America
(starting 41 Mya [Science 21
April 2006]) and Australia (35 Mya), allowing the
formation of a circumpolar current. This causes the climate
to become cooler and drier, and an ice cap starts forming on
Arctic ocean remains unfrozen.
|32||The origin of the C4 photosynthesis pathway in grass, at a time of declining carbon dioxide levels, which fixes carbon to form carbohydrates at higher temperatures and lower CO2 levels [Science Nov 2008].|
this time grasses begin to expand and diversify. Almost all
agriculture depends on it,
for grazing animals and cereal crops such as wheat and rice.
|20-12||The chimpanzee and hominid lines evolve.|
relatively warm conditions during the Pliocene come to an end as North
and South America become joined at Panama. This
was brought about by a
shift of the Caribbean plate, which moved slightly eastwards and formed
a land bridge across the Isthmus of Panama. The formerly
ecosystems merge, leading to minor extinctions, while the Pacific and
Caribbean marine ecosystems begin to diverge. The Atlantic
now cut off from the Pacific, develops a complex current system that
leads to increased snowfall in North America, which accumulates into
ice sheets, starting the current ice age. The tectonic plates
India and Asia also collided, which formed the Himalayan Mountains.
Generally the climate of the Pliocene is thought to have been warmer than it is today. The warmest phase was in the middle of the epoch, the interval between 3 and 4 million years ago. The climate was especially mild at high latitudes and certain species of both plants and animals existed several hundred kilometers north of where their nearest relatives presently exist. Carbon dioxide levels were around 380 ppm, similar to today, while temperatures were 3° C higher. Less ice at the poles also resulted in a sea level that is thought to have been about 25 meters higher than it is today.
|2-0.01||The current ice age begins, with cycles of roughly 100,000 years of ice followed by about 10,000 to 15,000 years of a warm inter-glacial period.|
|0.01||The current inter-glacial period (the so-called Holocene epoch) begins.|
Much like the past in reverse (WAR1)
interglacial period is due to end soon. Carbon dioxide released by
burning fossil fuels may introduce climate instability, and/or may
temporarily delay the return of the ice age.
exhausted, carbon dioxide is absorbed by vegetation and
weathering. The age of glaciation returns.
||Increasing warmth from the sun puts and end to glaciation. Carbon dioxide continues to be absorbed until levels become too low to support plant life. The continents begin to coalesce, forming a new Pangea Ultima, creating conditions similar to those at the time of the Permian extinction.|
from ever increasing temperatures and lack of carbon
dioxide. Animal life dies on land, becoming confined to the
life ends, and bacterial
is confined to the oceans, until they are evaporated by rising
its red giant phase, expanding until it reaches Earth's orbit.
Life may persist on moons in the outer solar system until the
|Carbon dioxide through time, as computed with GEOCARB,
computer program for estimating past levels of carbon dioxide. Each of
the bullets designate a mass extinction, and they can be seen to
correspond either with high or sharply increasing carbon dioxide levels.
From: Peter Ward, Under a Greening Sky, page 135.
|The evolving deep ocean. In the traditional model, oxygenation of the ocean occurred 1.8 billion years ago, with only brief recurrence of ferruginous conditions during later global glaciations (11). Canfield et al. now suggest that widespread deep-ocean anoxia lasted to 540 million years ago and perhaps a little longer. Instead of early oxygenation, after 1.8 billion years ago the deep ocean was dominated by H2S, followed by a repeat of widespread iron conditions (1).|
|Natural History Overview
|WAR1||The Life and Death of Planet Earth, by Peter D. Ward and Donald Brownlee, 2003. This book presents the case (known as the Rare Earth Hypothesis) that life on Earth is dependant on a number of unusual events, and that similar planets are likely to be rare throughout the galaxy. Of particular interest is the theory that plate tectonics, vital in many ways to keeping the Earth habitable, was made possible only by the impact on the young Earth that formed the Moon. The projections into the future on this page are based on this book.|
|HAZ1||Genesis, the Scientific Quest for Life's Origins, by Robert M. Hazen, 2005. Hazen introduces the theory of emergence, where complexity emerges from simpler elements when energy is applied. He then examines the possible orgins of life from the perspective of chemistry, geology and astrophysics.|
by Lynn Margulis and Dorian Sagan, 2000. An introduction to
history of life on Earth, with particular attention to the microbiology
of the Precambrian Era.
Life, edited by Stephen Jay
Gould, 2001. A history of the
evolution of life.
a Natural History of the First Four Billion Years of Life on Earth,
by Richard Fortey,
1997. A very readable summary of the history of life on
written by a paleontologist. The first chapter on the origin
life presents as fact that the first bacteria were extremophile
archaea, which is only one of many hypotheses, but the rest of the book
Earth, An Intimate History,
by Richard Fortey, 2004. An account of the geology of the
Earth, told from the perspective of his personal travel to various
locations around the world of geological interest.
|WAR4||Under a Green Sky, by Peter Ward, 2007. This book is an attempt to bridge the "canyon" that exists between climate scientists for whom paleoclimate is the study of the Pleistocine ice ages, and paleontologists who investigate the major mass extinctions that have afflicted the earth many times in the more distant past. This subject has been dominated in recent decades by hypothesis that the end-Cretaceous extinction was caused by a massive meteorite strike. After this was established to be fact, the search was on for the evidence of the impacts that caused the other mass extinctions. But no convincing evidence has been found. Instead, Ward has discovered a patterm to many extinctions involving increased greenhouse gases from flood basalt eruptions leading to ocean anoxia and hydrogen sulfide gas poisining. A parallel is drawn to the global warming in progress today. Unfortunately, in the last three chapters this book degenerates into hysteria riddled with basic scientific errors. Read with caution, or skip it altogether.|
|Precambrian Origin of Life
of Life - The
Discovery of Earth's Earliest Fossils,
by J. William Schopf,
1999. An account of the fossil evidence for bacteria and
Eukaryotic organisms in the Precambrian era. Schopf supports
early origin of cyanobacteria and oxygenation of the
atmosphere. First few chapters here,
critical opinion here.
Earth, by Gabrielle Walker,
2003. A very readable account of
the development of the theory of worldwide glaciations at the end of
Precambrian era. Also, here is a 2002
paper by Hoffman and Schrag
giving a detailed account of this
idea. Here is a negative
of the book. OK, so there is a low fact to chatter
ratio. Still, it was pleasant to read, and I liked the insight into how
geologists actually work. A valid criticism is its bias
toward the snowball hypothesis, but the reviewer does not mention that,
because he clearly supports the hypothesis as well.
the Blink of
an Eye, by Andrew Parker,
2003. An account of the Cambrian
Explosion, based on the idea that it was triggered by the first species
(a trilobite) that developed eyes, which enabled effective predation
and forced the rapid evolution of itself and all other
species. But first see this critical
review by Simon Conway Morris,
an expert on the Burgess Shale
Cambrian fossils. Eyes probably evolved long before the
trilobites were not the first Cambrian species,
and their calcite eyes are unique.
to Evolution, by Richard Fortey,
2000. Although focused on
trilobites, chapter five of this book has the best description of the
so-called Cambrian Explosion I have seen. In general, a very
written book, highly recommended.
Creation - The Burgess Shale and the Rise of Animals,
Conway Morris, Professor of Evolutionary Paleobiology, University of
Cambridge, 1999. This book is partly a response to the
Wonderful Life by Stephen Jay Gould. He takes issue with
hypothesis that complex life began with a large number of phyla (body
plans), and disparity has been reduced over time. He also
criticizes the idea that the form of today's life is purely a matter of
contingency. Read the very detailed review.
|Permian / Triassic
|BEN1||When Life Nearly Died - the Greatest Extinction of All Time, by Michael J. Benton, 2003. An investigation of the Permian mass-extinction. This book presents very recent data that indicates this extinction was more severe both on land and on sea than previously thought.|
Obsession, Paleontology, and the Greatest Catastrophe on Earth,
2004. A first hand account of ten years of investigation into
sequence and causes of the Permian mass extinction. A case
rapid (50,000 years or less) extinction is methodically
presented. The last two chapters then fast forward into a
conclusion that de-oxygenation of the oceans and atmosphere was the
means of extinction, without nearly the same amount of supporting
levels dropped, exposing anoxic organic
materials to the atmosphere. The newly-exposed materials oxidized,
out of the air, and the iron in these materials rusted, creating the
layers that are so distinctive in post-Permian geology. Explosive
eruptions from Siberia may have contributed to this loss of oxygen as
expelling huge amounts of carbon dioxide, carbon monoxide, methane, and
gases into the atmosphere.
He also deals critically with the Luann Becker
hypothesis that the extinction was caused by a meteor impact.
|Cretaceous Tertiary Extinction
Science of Mass Extinctions, by Vincent Courtillot,
first presents the evidence for the Chicxulub impact being the cause of
the K/T extinction. He then develops a theory of how plumes
deep within the mantle cause flood basalt eruptions, and that these are
the major cause of mass extinctions.
by Simon Conway Morris, 2003. This book has three
parts. First, he presents the hypothesis that Earth-like planets are
the universe, similar to Ward's Rare Earth. Then he presents
convincing demonstration of how little progress has been made in
discovering the origin of life. Finally, most of the book
many examples of how many aspects of living thing have evolved more
than once. The hypothesis is that while many lifeforms are
theoretically possible, there are only a limited number of forms that
actually work, and evolution tends to converge towards those forms.
|WAR3||Out of Thin Air, by Peter Ward, 2006. The thesis of this book, in its own words, is: The history of atmosphereic (and hence oceanic) oxygen levels through time have been the most important factor in determining the nature of animal life on Earth - its morphology and basic body plans, physiology, evolutionary history, and diversity. This hypothesis means that the level of oxygen influenced every large-scale evolutionary adaptation or innovation in the history of animal life on Earth, and that oxygen levels dictated evolutionary originations, extinctions, and the architecture of animal body plans.|
Evolutionary Biology of
Plants, by Karl J. Niklas, 1997. Comprehensive and rather
|My Related Sites: Paleoclimate provides the history of climate change for the last half billion years. See also the Science of Climate Change for an explanation of global warming issues in the context of Earth's past.|
||The Paleomap Project. This superb site links the changing arrangement of the continents due to plate tectonics with changes in the Earth's vegetation and climate. The Paleogeographic Atlas Project, from the University of Chicago, had detailed maps spanning a shorter period of time.|
|2||The Tree of Life Web Project. An extensive model of the relationship between all living things, in tree form.|
||Plant Evolution Tour. This site gives detailed information about the evolutionary history of plants.|
page was originally inspired by a
time line created by Niel Brandt
found at the Talk
|5||Major Events in the History of Life. A more detailed summary of evolutionary history.|
|6||A detailed examination of changing sea level from the Paleozoic Era (542 to 251 million years ago) is found in [Science Oct 2008].|
Impacts and Flood Basalt Eruptions
are two natural
catastrophes that are linked to mass extinctions:
Meteorite impacts are well known as the cause of the end-Cretaceous mass extinction, and are linked to some other extinction events as well. Only impacts on land (or continental shelves) persist; impacts into the majority of the Earth's surface covered by ocean quickly disappear. As well, comets and loosely packed meteorites (see the article Are Asteroids Rubble Piles) may not leave craters at all, but may explode in the atmosphere, as happened at Tunguska in Siberia in 1908. Therefore the meteorite record is only partially known.
Flood basalts are massive eruptions of lava from deep below the surface. While a large volcano may discharge a few cubic kilometers of lava in its lifetime, the largest flood basalts are measured in millions of cubic kilometers, covering thousands of square miles. Large amounts of dust and gas are released into the atmosphere. Flood basalts can be linked to almost every mass extinction, including the end-Cretaceous event commonly attributed to meteorite impact.
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