A Brief History of Life on Earth

A Brief History of Life on EarthA Brief History of Life on EarthGeology Today

Chapter 15Barbara W. Murck and Brian J. Skinner

N. Lindsley-Griffin, 1999

Horned dinosaurs, 70 m.y. ago

Mark Marcuson; Nebraska State Museum

Amino acids are the basic building blocks of proteins.

Biosynthesis is the linking together (or polymerization) of small organic molecules (like amino acids) to form larger ones, called biopolymers (like proteins).


Organization of LifeOrganization of Life


DNA - Deoxyribonucleic acid - is a double-chain biopolymer that consists of two twisted chain-like molecules held together by organic molecules.

DNA contains all the genetic information needed for organisms to grow and reproduce.

DNA stores genetic information.

Fig. 15.7, p. 443


RNA - Ribonucleic acid - is a single-strand molecule similar to one-half of a DNA strand.

RNA contains the information needed to construct an exact duplicate of the protein molecule.

RNA transmits the genetic information that DNA stores.

Fig. 15.7, p. 443



Metabolism is the set of biochemical reactions by which organisms produce and extract food energy.

Fermentation is anaerobic metabolism - without oxygen.

Respiration is aerobic metabolism - with oxygen.


Short chain of fossil cyanobacteria cells, 1.0 b.y. Bitter Springs Chert, N. Australia

Living cyanobacterium Oscillatoria


Oxygen in Atmosphere

Oxygen in Atmosphere


Photosynthesis - process whereby plants use light energy to cause carbon dioxide to react with water.

Byproducts are:

Organic substances - carbohydrates

and free oxygen

All free oxygen now in the atmosphere originated by photosynthesis.

Fig. 15.3, p. 439

Early EarthEarly Earth

Major events and trends in Earth’s surface environment during the first 4.0 b.y.:

Ocean forms, 4.4 b.y.

Oldest bacteria, 3.8 b.y.

Blue-green algae, 3.0 b.y.

Iron formations, 2.2 b.y.

Oxygen buildup, 2.0 b.y.

Eukaryotes, 2.0 b.y.

Abundant multicelled

fossils, 0.6 b.y.

Fig. 15.1, p. 437


Early Earth 4.6 b.y.

Early Earth 4.6 b.y.

The solar system coalesced 4.6 b.y. ago from a cloud of cosmic dust and gas.

Gravitational compaction caused nuclear fusion to begin in the sun.

Planetesimals gathered into larger clusters to make planets; leftover material formed asteroids and comets.

N. Lindsley-Griffin, 1999Nebula M16

Asteroid Ida

Early Earth4.5 b.y.

Early Earth4.5 b.y.

Probably molten at first, Earth was battered by repeated impacts of planetesimals.

The first atmosphere was stripped away by solar wind or impacts, but was replenished by volcanic eruptions.

It was too hot for water to exist on the surface.

N. Lindsley-Griffin, 1999John Drummond; Time-Life Books

Early Earth4.4 b.y.

Early Earth4.4 b.y.


As Earth cooled, water vapor in the atmosphere condensed and rained out to form oceans - maybe as early as 4.4 b.y. ago.

Don Davis; Time-Life Books

Early Life3.8 b.y.

Early Life3.8 b.y.


Near the end of the intense bombardment period, about 3.8 b.y. ago, Earth still was wracked by meteorite impacts and volcanic eruptions. It was a tough place to make a living.

Don Davis; Time-Life Books

Origin of LifeOrigin of Life

The first life required chemosynthesis of organic compounds - such as amino acids -

from inorganic materials like atmospheric gases,

to make proteins.


Lightening bolts discharge through volcanic gases, Mt. Pinatubo, Philippines

Fig. 15.4, p. 441


One hypothesis suggests simple microbes first formed in aerosols - tiny liquid droplets or solid particles suspended in the atmosphere.

Could lightening discharges have provided the energy?


Lightening bolts discharge through volcanic gases, Mt. Pinatubo, Philippines

Fig. 15.4, p. 441

Because of the adverse surface conditions, the most likely place for life to develop might have been at deep ocean thermal springs, protected from meteorite bombardment.Both the raw materials and the heat needed for chemosynthesis would have been available here.


Black smoker

Galapagos Is.

Fig. 15.6, p. 443


The first life was microbial.

Oldest fossils of microbes found on Earth (so far) are nearly 3.5 b.y. old.

Rocks in Greenland thought to have formed as byproducts of microbial activity are 3.8 b.y.


Short chain of fossil cyanobacteria cells, 1.0 b.y. Bitter Springs Chert, N. Australia

Living cyanobacterium Oscillatoria

Origin of Life3.5 b.y. +?

Origin of Life3.5 b.y. +?

Mars Life?4.5-3.6 b.y.Mars Life?4.5-3.6 b.y.

Meteorite ALH84001 was

found in Antarctica in 1984.

It is 4.5 b.y. old.

Its chemistry is unlike Earth rocks - instead, it is like Mars rocks analyzed by remote landers.

It is thought to have originated on Mars, but was “splashed” into space by an impact near the end of the heavy bombardment period. It remained in space until about 16,000 years ago, when it was attracted by Earth’s mass and fell onto Antarctica.


Fig. 15.5, p. 442

In 1996, tiny tube-like

structures were discovered

inside the meteorite.

Some scientists have interpreted these structures as fossils of microbes - if so, they would be at least 3.6 b.y. old.

The debate is raging hotly - stay tuned for further developments.


Fig. 15.5, p. 442

Mars Life?4.5-3.6 b.y.Mars Life?4.5-3.6 b.y.


Chemical sediments from 2.0 to 1.8 b.y.

consist of oxygen-poor iron minerals

plus oxygen-rich iron minerals

Interlayering reflects a transition from oxygen-poor atmosphere to oxygen-rich atmosphere during this time.

Brockman Formation, 2.0 b.y., W. Australia (Fig. 8.10, p. 227)

Oxygen Atmosphere

1.8 b.y.

Oxygen Atmosphere

1.8 b.y.

Early LifeEarly LifeAll organisms are composed of cells, a

complex grouping of chemical compounds

enclosed in a membrane, or porous wall.

Prokaryotic cells store their DNA in a poorly defined part of the cell, not separated from the cytoplasm - the main body of the cell - by a membrane.


Prokaryotic cell lacks a well-defined nucleus

Fig. 15.8, p. 445

Early LifeEarly Life

Eukaryotic cells include a distinct nucleus surrounded by a membrane, as well as other membrane-bounded organelles - well defined parts that each have a specific function.


Eukaryotic cell has a well-defined, membrane-bound nucleus

Fig. 15.8, p. 445

Early LifeEarly Life

Prokaryotic cells are the earliest and simplest cell forms; many are anaerobic. Modern bacteria are prokaryotes.

N. Lindsley-Griffin, 1999Fig. 15.8, p. 445

Eukaryotic cells are larger and more complex; most require oxygen.Most advanced life forms are Eukaryotes.

How Fossils FormHow Fossils Form

Mineralization - bones and other hard parts are replaced by minerals carried in solution by groundwater.

Petrified wood has been replaced by mineralization.

Even though its original woody texture is preserved, it consists entirely of minerals like crystalline quartz, chalcedony, or agate.


Petrified Forest Natl. Park, Arizona

Fig. 15.16, p. 455


Trace fossils are indirect evidence of organisms:

tracks and trails

wormholes and burrows

nests

feces (coprolites)

calcite mounds (stromatolites)

Dinosaur tracks, 65 m.y.a.

Fig. 15.18, p. 455


Some organisms are frozen in permafrost, like this wooly mammoth.

Some organisms are trapped and preserved whole in amber or tar, like this Eocene to Oligocene age mosquito.

(Fig. 15.15, p. 454).N. Lindsley-Griffin, 1999


EvolutionEvolution

Charles Darwin visited the Galapagos Islands in 1832.

He observed many species of finches on the islands, whereas only one lives on the nearby continent of South America.

Each finch species occupies a different environment, and eats different food. Their beaks and their feeding behavior vary to exploit the sparse resources as effectively as possible.


Darwin’s Finches

Fig. 15.13

p. 451

EvolutionEvolution

To explain his observations, Darwin hypothesized that species can adapt to new conditions through natural selection.

Individuals who are well-adapted are more likely to pass on their characteristics to the next generation.

Individuals who are poorly adapted tend to be eliminated and are less likely to produce offspring to perpetuate their genes.


Darwin’s Finches

Fig. 15.13

p. 451

EvolutionEvolution

All natural populations have individuals with different characteristics. In any setting, some features work better than others, and these individuals will tend to reproduce more successfully.

Over time, the entire population will evolve towards a better adaptation.


Darwin’s Finches

Fig. 15.13

p. 451

EvolutionEvolution

Back to Darwin’s Finches --

A study of DNA released in mid-1999 showed that all the Galapagos finches are closely related to each other.

They probably were derived from the South American finch that Darwin hypothesized was their common ancestor.


Darwin’s Finches

Fig. 15.13

p. 451

EvolutionEvolution

The iguana problem:

Galapagos Islands are only 3 m.y. old.

DNA from Galapagos iguanas shows that they have evolved about 7 m.y. since splitting off from their South American cousins.

BUT -- The islands did not even exist when the iguanas left South America 7 m.y. ago.


Galapagos Iguana

Fig. B15.1, p. 452

EvolutionEvolution

The iguana problem (Cont.):

The Galapagos Islands are a hot spot chain like Hawaii, in which the older volcanoes have subsided below sea level.

Hypothesis: the ancestral iguanas swam from South America to the easternmost island. As time passed and each island in the chain subsided, they moved west to the next one. It took them 7 m.y. to make the trip.


Galapagos Iguana

Fig. B15.1, p. 452

3.5 b.y.: The oldest known fossils are chains of prokaryotic cells from a chert in W. Australia.

Notice how similar they are to the possible microbes in Mars meteorite ALH84001


Fossil Record - ArcheanFossil Record - Archean

Stromatolites are layers of calcium carbonate that form in warm, shallow seas by the activities of photosynthetic bacteria.

Fossil stromatolites > 1.5 b.y. are evidence of microbial activity during the Proterozoic and Archean (as far back as 3.0 b.y. or earlier).

N. Lindsley-Griffin, 1999Stromatolites, Shark’s Bay, W. Australia (Fig. 15.10, p. 447)

Fossil Record - PrecambrianFossil Record - Precambrian

About 1.4 b.y.a. - oldest eukaryotes

By 1.0 b.y.a. - eukaryotes common

600 m.y. - Ediacara fauna: oldest fossils of larger, multicellular, soft-bodied marine animals.

Named for Ediacara Hills, Australia.


Fossil Record - Proterozoic

Fossil Record - Proterozoic

Mawsonia spriggi - a floating, disc-shaped animal like a jellyfish, 13 cm across.

Dickinsonia costata - worm-like, 7.5 cm across

Fig. 15.11

p. 448

Ediacaran Fauna are still poorly understood.

Some are simple blobs, others are like jellyfish, worms, or soft-bodied relatives of the arthropods.

They appear worldwide in strata about 600 m.y. old, suggesting a relatively sudden explosion of soft multicelled forms.


Fossil Record - Late ProterozoicFossil Record - Late Proterozoic

Plants: Land plants probably evolved from green algae about 600 m.y. ago. Life on land may have looked like this.

In the seas, bacteria and green algae were common at the end of the Precambrian.


Green algae

(Fig. 15.22, p. 458)

Fossil Record - Late ProterozoicFossil Record - Late Proterozoic

545-505 m.y.a. - beginning of period of great diversification:

Higher atmospheric oxygen affected skeletal biochemistry and supported larger organisms.

Ozone developed to level where it blocked ultraviolet radiation.

Eukaryotes invented sexual reproduction.

Hard parts appeared.


Fossil Record - Cambrian


Trilobite, Utah (Fig. 15.20)

Soft-bodied arthropod, B.C.

(Fig. 15.21, p. 457)

545-505 m.y.a.:

Hard external skeletons protected trilobites, clams, snails, and sea urchins from predators.

Soft-bodied animals diversified from Ediacaran fauna into the Burgess Shale fauna.

Gills, filters, efficient guts, circulatory systems, and other features of more advanced life forms developed.




Trilobite, Utah (Fig. 15.20)

Soft-bodied arthropod, B.C.

(Fig. 15.21, p. 457)

Fossil Record - CambrianFossil Record - Cambrian

545-505 m.y.a.: reconstruction of Burgess Shale fauna

N. Lindsley-Griffin, 1999 J. Wiley & Sons, The Blue Planet

490-443 m.y.a.: Seas held abundant marine invertebrates with sophisticated adaptations to different conditions.

Straight-shelled cephalopods, trilobites, snails,

brachiopods, and corals in a shallow inland sea.


Fossil Record - OrdovicianFossil Record - Ordovician

The Field Museum, Chicago

Fossil Record - SilurianFossil Record - Silurian

438-408 m.y.a.: This was the “Golden Age” of cephalopods and brachiopods (a clam-like shellfish).

The first land plants developed, and the first arthropods (scorpion-like invertebrates) ventured onto land.

N. Lindsley-Griffin, 1999 The Milwaukee Museum

Fossil Record - DevonianFossil Record - Devonian

408-360 m.y.a.: The “Golden Age” of fishes

N. Lindsley-Griffin, 1999 American Museum of Natural History, New York

Lutgens and Tarbuck, 1999

408-360 m.y.a.: Land plants became common. Vascular plants developed - club mosses and ferns.

These plants had structural support from stems and limbs and a vascular system providing an internal plumbing system for water.


Fossil Record - DevonianFossil Record - Devonian

Modern fern leaf with dark spores on underside

Fossil fern in shale, 350 m.y. (Fig. 15.23, p. 459)

380-360 m.y.a. - First seed plants - the naked-seed plants - developed. Gymnosperms like Glossopteris developed.

Ginkgos are long-lived relics of the ancient family of naked-seed plants, so are conifers.


Fossil Record - Late DevonianFossil Record - Late Devonian

Modern and fossil ginkgo leaves (Fig. 15.24, p. 459)

360-286 m.y.a.: Age of amphibians; first winged reptiles and first winged insects. Widespread forests and swamps.

Ichthyostega had features like a tail that it inherited from fish; and legs that allowed it to move around on land.

N. Lindsley-Griffin, 1999 Michael Rothman; John Wiley & Sons

Fossil Record - CarboniferousFossil Record - Carboniferous

Fig. 3.9, p. 65

320-290 m.y.a.: peat swamps common, with scale trees, seed ferns, scouring rushes, and large dragonflies


Fossil Record - PennsylvanianFossil Record - Pennsylvanian

The Field Museum, Chicago

286-248 m.y.a.: Amphibians decline; reptiles and insects increase; first mammal-like reptiles appear. Nonseed plants decline.


Fossil Record - PermianFossil Record - Permian

Eryops, a carnivorous amphibian -The Field Museum, Chicago

Fossil Record - TriassicFossil Record - Triassic 225 m.y.a.: First dinosaurs and mammals; explosive radiation of dinosaurs. (Primitive Ornithischia, an early dinosaur)

N. Lindsley-Griffin, 1999 National Museum of Natural Sciences, Canada

Fossil Record - JurassicFossil Record - Jurassic

213-144 m.y.a.: The Age of dinosaurs; forests of gymnosperms and ferns cover most of Earth

J.R. Griffin, 1999 Smithsonian Natural History Museum

Fossil Record - JurassicFossil Record - Jurassic

213-144 m.y.a.: Age of dinosaurs


American Museum of Natural History, New York, N.Y.

213-65 m.y.a.: Age of dinosaurs. Birds appear.

N. Lindsley-Griffin, 1999 Breck Kent; John Wiley & Sons

Fossil Record - Jurassic and CretaceousFossil Record - Jurassic and Cretaceous

Fig. 3.9, p. 65

Dragonfly, Brazil

7 cm (3 in.) long

Fig. 15.26, p. 460

175-65 m.y.a. :

This nesting mother, a birdlike dinosaur called Oviraptor, was found curled protectively around a nest containing at least 20 eggs - evidence that dinosaurs cared for their young.


Fossil Record - Jurassic -Cretaceous

Fossil Record - Jurassic -Cretaceous

Archaeopteryx: an early bird, has skeleton and teeth very similar to those of dinosaurs as well as detailed impressions of feathers.

Fig. 15.27, p. 462

Fossil Record - CretaceousFossil Record - Cretaceous

144-65 m.y.a.: Plesiosaurs infested the beaches

N. Lindsley-Griffin, 1999 Smithsonian Natural History Museum

144-65 m.y.a. - first flowering plants appear.

After the K-T boundary, flowering plants diversify and spread explosively over the planet, as do mammals.


Fossil Record - Cretaceous and TertiaryFossil Record - Cretaceous and Tertiary

Fossil sweet gum, 1.5 m.y., Idaho - next to modern sweet gum fruit (Fig. 15.25, p. 459)

Fossil Record - K-T BoundaryFossil Record - K-T Boundary

65.0 m.y.a.:

Cretaceous -Tertiary Boundary

Many species and genera, including the dinosaurs, died out at end of Cretaceous

One hypothesis: Earth was hit by a meteorite - at Chixulub, in the Yucatan area of Mexico

Planetary Society, J.R. Griffin, 1999

Fossil Record - Tertiary: PaleoceneFossil Record - Tertiary: Paleocene

65-54.9 m.y.a.: Beginning of modern life forms following the K-T Boundary extinctions.

Age of mammals began, grasslands spread.


U.S. Geological Survey

Fossil Record - Tertiary: EoceneFossil Record - Tertiary: Eocene54.8-38 m.y.a.


Fossil Record - Tertiary: OligoceneFossil Record - Tertiary: Oligocene

38.0-24.6 m.y.a.: horses, antelopes, cats, oreodonts


American Museum of Natural History, New York

Fossil Record - Tertiary: MioceneFossil Record - Tertiary: Miocene

24.6-5.1 m.y.a.: horses, antelopes, and other mammals.

N. Lindsley-Griffin, 1999 Breck Kent; John Wiley & SonsFig. 3.9, p. 65

Fossil Record - Tertiary: MioceneFossil Record - Tertiary: Miocene



24.6-5.1 m.y.a.: horses, rhinoceri, and elephants.

Fossil Record - Quaternary: PleistoceneFossil Record - Quaternary: Pleistocene

2.0-0.1 m.y.a.:

deer family and elephant family



2.0-0.01 m.y.a.: horses, cats, elephants, bison, dire wolves




2.0-0.01 m.y.a.: mammals successfully colonized all environments

J.R. Griffin, 1999 Larson, Illinois State Museum


2.0-0.01 m.y.a.:

subglacial

areas,

La Brea tar

pits, S. CA


Fossil Record - Quaternary: PleistoceneFossil Record - Quaternary: Pleistocene < 0.1 m.y.a.: Western Nebraska when first humans were appearing

N. Lindsley-Griffin, 1999 Mark Marcuson, Nebraska State Museum

Fossil Record - QuaternaryFossil Record - Quaternary

4.4-0 m.y.a.: Hominids diverged from an early ape-like family. (Poor fossil record and missing transitional forms complicate the story and leave many gaps, but new fossils are being found each year.)

Ardipithecus ramidus - 4.4 (bipedal, erect forest dweller)

Ardipithecus anamensis - 4.2-3.9 (bipedal, apelike skull)

Australopithecus afarensis (“Lucy”) - 3.9-2.8 (bipedal, apelike face with sloping forehead, human-like bodies. Lived together in family groups.)

and other species of Australopithecus - 3.0-1.1

Homo habilis - 2.2-1.6 m.y.a. (used stone tools, so

may be related to Homo sapiens, but skull is like

australopithecines)


Homo habilis

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Fossil Record - QuaternaryFossil Record - Quaternary

Hominids (Cont.)Homo erectus - 1.8-0.4 m.y. (Peking man,

Java man: developed large brains, tools,

weapons, fire, and learned to cook food.)

Homo sapiens archaic - 500-200 t.y.a.

(Skulls intermediate between Homo erectus

and Homo sapiens sapiens)

Homo sapiens neandertalensis -200-30 t.y.a

(teeth and brain similar to ours,

but DNA different, burial sites suggest

they practiced some form of religion.)


Neandertal

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Fossil Record - Quaternary: Holocene

Fossil Record - Quaternary: Holocene

Homo sapiens sapiens -

120,000-present


A Brief History of Life on Earth

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