IV. Early Life

History of Life

I. Earth History

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I. Earth History

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IV. Early Life

- the first cells were probably heterotrophs that simply absorbed nutrients and ATP from the environment.

- as these substances became rare, there was strong selection for cells that could manufacture their own energy storage molecules.

- the most primitive cells are methanogens, but these are NOT the oldest fossils.

IV. Early Life

- the second type of cells were probably like green-sulphur bacteria, which used H2S as an electron donor, in the presence of sunlight, to photosynthesize.

I. Earth History

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Stromatolites - communities of layered 'bacteria'

IV. Early Life

- the evolution of oxygenic photosynthesis was MAJOR. It allowed life to exploit more habitats, and it produced a powerful oxidating agent! These stromatolites, which date to > 3 bya are microbial communities.

I. Earth History

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IV. Early Life

- about 2.3-1.8 bya, the concentration of oxygen began to increase in the ocean and oxidize eroded materials minerals... deposited as 'banded iron formations'.

I. Earth History

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IV. Early Life

- 2.0-1.7 bya - evolution of eukaryotes.... endosymbiosis.

IV. Early Life

Eukaryote Characteristics

- membrane bound nucleus

- organelles

- sexual reproduction

http://micro.magnet.fsu.edu/cells/animalcell.html

I. Earth History

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I. Earth History

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I. Earth History

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I. Earth History

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I. Earth History

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4.5 million to present

(1/1000th of earth history)

I. The "Precambrian"

http://www.ucmp.berkeley.edu/precambrian/precambevents.map


Vendian - 610 mya - 544 mya.

http://www.ucmp.berkeley.edu/precambrian/precambevents.map


- The Ediacaran (610-544)

The first fossil animals




Dicksonia - thought to be a segmented worm




Eoporpita - Cnidarian polyp




Cyclomedusa - Cnidarian polyp; up to 1 meter in diameter


- The Ediacaran(610-544)


Charnia - sea pen (related to Cnidarians) - up to 1 m long




Nemiana - may be a cnidarian or algal colony...




Pteridinium - cnidarian???




Arkarua - Echinoderm?




Spriggina - soft-bodied, but assignment to Annelida is doubtful... some describe it as a soft-bodied arthropod...(it is similar to trilobites...)

Spriggina

trilobite




Tribrachidium - soft-bodied, but enigmatic... maybe a cnidarian or an echinoderm..???




Kimberella - recent analysis suggest it might be an early mollusc.. a bit chiton-like...

http://www.ucmp.berkeley.edu/vendian/kimberella.html




Largely a radiation of soft-bodied forms.

In addition, however, the first predatory animals (Cnidarians...)

So, although rare, there is a radiation of soft-bodied organisms before the Cambrian... and representatives from several major phyla (or sister phyla) appear.

II. The Paleozoic Era

A. The Cambrian Period (544 - 510 mya)

- an 'explosion' of fossil animals:




- representatives of nearly all modern phyla (no Bryozoans)

- representatives of extinct phyla

- radiation of animals with hard parts




examples of extant phyla:

Thaumaptilon

Sea Pen - Cnidaria





Sydneyia - Arthropod





Canadia - Annelida





Choia - Porifera





Aysheaia - Onychophora





Ottoia - Priapulida





Canadapsis - Arthropoda (Crustacea)





Waptia - Arthropoda (Crustacea)





Leanchoilia - Arthropoda (Crustacea)





Pikaia - Chordata





Hallucigenia - Onychophora




examples of EXTINCT phyla or subphyla:

Olenoides – Trilobita (Arthropoda)





Marella - primitive Arthropod





Haplophrentis - Hyolithid




examples of organisms unassigned to any major group:

Opabinia





Amiskwia





Anomalocaris





Wiwaxia



Burgess Shale Community



WHY?



- First major radiation of hard-bodied org's

WHY?




Sampling Error? Since hard-parts fossilize better than soft parts, is the 'Explosion' just a reflection of the greater likelyhood of fossilization?




Sampling Error? Since hard-parts fossilize better than soft parts, is the 'Explosion' just a reflection of the greater likelihood of fossilization?

Predation? The Vendian radiation contained lots of predators..Cnidarians. Hard parts would be adaptive protection against these predators, as well as the predators in the Cambrian.











Also, it's important to realize that this "Explosion" occurred over 10 my.... not 'instantaneous'...




Our first example of innovation, radiation, and competitive contraction





Hard parts









I. The Precambrian

- Vendian

II. Paleozoic

A. Cambrian

- The Cambrian 'Explosion'

- The Cambrian Fauna and Beyond


The fauna was dominated by trilobites...

and the number of trilobite families peaked in the late Cambrian and declined through the Paleozoic. This marine fauna is known as the 'Cambrian Fauna' and represents the first great marine faunal assemblage in the fossil record.


This fauna was replaced by the 'Paleozoic' ( or Brachiopod) fauna, and then by the Modern (or 'Gastropod-Mollusc') fauna in the Mesozoic.


- What contributes to these patterns in diversity?



Some paleontologists suggest a correlation between large scale diversity patterns and plate tectonics.

http://www.jamestown-ri.info/prelude.htm



Some paleontologists suggest a correlation between large scale diversity patterns and plate tectonics.

This is the supercontinent "Rodinia". It formed about 1 billion years ago, and began to break up in the Cambrian (544-510) and Ordovician (510-439).

http://www.jamestown-ri.info/prelude.htm



So, we have 'vicariance' at a large geologic scale, increase the abundance of shallow coastal habitats and the possibility of allopatric speciation, divergence, and radiations.

A similar radiation in diversity occurs in the Mesozoic when Pagaea breaks up... creating more shallow coastal areas...



1) Vicariance

2) Nutrient Loading



1) Vicariance

2) Nutrient Loadingincrease in shallow seas increases marine productivity and might increase food chain lengths and diversity.

also, evolution of more productive terrestrial biotas would increase nutrient contributions from runoff.



1) Vicariance

2) Nutrient Loading

3) Mass Extinctions

Ice Age

Impact, C

limate

Vulcanism

I. The Precambrian

- Vendian

II. Paleozoic

A. Cambrian (544-510 mya)

I. The Precambrian

- Vendian

II. Paleozoic


- evolution of chordates

Cephalochordata

Craniata

Euchordata Hagfish (skull but no vertebrae...)

Vertebrata

Pikaia

Myllokunmingia 530 mya

Haikouichthys 530 mya

I. The Precambrian

- Vendian

II. Paleozoic


- evolution of chordates


Nature 1999


Haikouichthys ercaicunensis

early Cambrian

perhaps more advanced than Myllokunmingia,

but both may have had cartilaginous vertebrae... the first true verts!

Nature 2003

I. The Precambrian

- Vendian

II. Paleozoic


B. Ordovician (510-439 mya)

I. The Precambrian

- Vendian

II. Paleozoic



I. The Precambrian

- Vendian

II. Paleozoic



I. The Precambrian

- Vendian

II. Paleozoic



- inverts

new trilobites

I. The Precambrian

- Vendian

II. Paleozoic



- inverts

new trilobites

Nautiloid radiation

During the middle Ordovician some long-shelled forms like Endoceras and Cameroceras attained lengths of 4 to as much as 10 meters - among the largest molluscan shells ever

I. The Precambrian

- Vendian

II. Paleozoic



Radiation of Ostracoderms SILURIAN

"Ostracoderms"

Heterostracans

Astraspids

Arandaspids

Lampreys**

Osteostracans

JAWED FISHES**Tree of Life phylogeny; differs from Cowens.

I. The Precambrian

- Vendian

II. Paleozoic



Astraspis

Arandaspida

"Ostracoderms"

Bony plates; no paired fins; gill arches

I. The Precambrian

- Vendian

II. Paleozoic



- plants

the first terrestrial plant fossils are fragmentary; they are spores and cuticles (which signify land plants). In all likelihood they are 'hepatophyte' liverwort-like non-tracheophytes...

I. The Precambrian

- Vendian

II. Paleozoic



C. Silurian (443-417 mya)

- inverts

Brachipods begin to dominate; 80% of all individuals


- inverts


Reef-building corals

radiate


- inverts


Reef-building corals radiate

Crinoid echinoderms radiate


- inverts




Eurypterids (sea scorpions) dominate (7 feet long)


- inverts




Eurypterids (sea scorpions) dominate; Horseshoe crabs

Semi-aquatic scorpions and terrestrial Chelicerata evolve

Millipedes first completely terrestrial animals


- inverts

- plants


- inverts

- plants

radiation of the first vascular plants

4 species of Cooksonia, including those representing the Rhyniophytes and Lycophytes


- inverts

- plants

- verts

C. Silurian (443-417 mya) - inverts - plants - verts

Radiation of Ostracoderms SILURIAN

"Ostracoderms"

Heterostracans

Astraspids

Arandaspids

Lampreys**

Osteostracans

JAWED FISHES**Tree of Life phylogeny; differs from Cowens.


- inverts

- plants

- verts

- Heterostracans - over 300 species; very abundant


- inverts

- plants

- verts

- Osteostracans

bottom-feeders, but with an important evolutionary advancement - paired fins


- inverts

- plants

- verts

- Jawed Fishes (Gnathostomes)

- Acanthodians


- inverts

- plants

- verts

- Jawed Fishes (Gnathostomes)

the oldest jawed fish fossils are Acanthodians... however, they are a group of bony fishes and it is likely that they were preceded by the cartilaginous Placoderms (which radiate in the Devonian)

I. The Precambrian

- Vendian

II. Paleozoic




D. Devonian (417-354 mya)

- "The Age of Fishes"


- inverts

crazy trilobite 50cm long.... Terataspis grandis


- inverts:

- Ammonites


- inverts:

- Ammonites

- Terrestrial Arthropods

- oldest spider - Attercopus

- mites

- trigonotarbids (no silk)


- inverts:

- plants

Lycopod forests, then

Progymnosperm forests dominated by one genus, Archaeopteris 20m


- inverts:

- plants

- verts:

- last of the ostracoderms...

Psammolepis over 2m


- inverts:

- plants

- verts:

- last of the ostracoderms...

- the major radiation of jawed fish groups

Lobe-finned Fishes

Ray-finned Fishes

Bony Fish

Acanthodians

Teleosts

Chondrichthyes (Sharks, rays)

PlacodermsArthrodires

Antiarchs


Fishes of the Middle Devonian locality of Lethen Bar, in Scotland (Givetian, about 377 Ma). They include antiarchs (1 Pterichthyodes); and arthrodire (2. Coccosteus) placoderms, acanthodians (3. Diplacanthus), ray-finned fish (4, Cheirolepis), lungfish (5, Dipterus), and osteolepiform lobe-finned fish (6. Osteolepis), representing the lineage that gave rise to land animals.


- Placoderms

- Sharks

- Lobe-finned Fishes

- Ray-finned Fishes

- Tetrapods (from lobe-finned fishes)


- Placoderms

- very abundant

- head shields

- shearing or crushing tooth plates

Dunkleosteus - 6m Arthrodire

Antiarch


- Placoderms

- Sharks

Stethacanthus - 2m


- Placoderms

- Sharks


- Placoderms

- Sharks

- Ray-finned Fishes


- Placoderms

- Sharks

- Ray-finned Fishes


- Placoderms

- Sharks

- Ray-finned Fishes



- Placoderms

- Sharks


385 mya

365 mya

Eusthenopteron

Panderichthys rhombolepis

Tiktaalik roseae

Acanthostega gunnari

Ichthyostega sp.

I. The Precambrian

- Vendian

II. Paleozoic





E. Carboniferous (359-300 mya)


- inverts

Arthropleura -largest terrestrial arthropod - 2m


- inverts

- radiation of insects

- evolution of flight

Meganeura monyi - largest insect ever

wingspan of 70 cm


- inverts

- plants

The early Carboniferous saw a reduction in the Devonian forests and a dominance of small plants - lycopods and their kin.

Lepidodendron

Psaronius - fern

Lebachia - progymnosperm

Cordaites - progymnosperm


- inverts

- plants

The early Carboniferous saw a reduction in the Devonian forests and a dominance of small plants - lycopods and their kin.

As the period proceeds, the giant lycopsid swamp forests evolve across the tropical continent of Euramerica.

There was lots of photosynthesis, but this was not balanced by decomposition (because much of the biomass was preserved in sediment, not broken down by decay). So, oxygen production by photosynthesis exceeded oxygen consumption by decomposition... and oxygen levels were probably very high...this may have allowed the enormous size of invertebrates.


- inverts

- plants


- inverts

- plants Coal deposits in shallow tropical swamps


- inverts

- plants

- vertebrates

sharks replace placoderms as dominant in oceans;

The golden age of sharks - 45 Families

(currently 21)


- inverts

- plants

- vertebrates


ray finned fishes dominate in fresh water

- vertebrates

radiation of stem tetrapods!!

- vertebrates


- vertebrates


"Anthracosaurs"


- inverts

- plants

- vertebrates


ray finned fishes dominate in fresh water

stem tetrapods radiate!

"crown" tetrapods

Seymouriamorpha

Temnospondyls

Ichthyostegans


- inverts

- plants

- vertebrates

stem tetrapods

Temnospondyls

a very diverse radiation of tetrapods, from alligator-like salamanders to large, scaled, frog-like creatures. Cowens places these ancestral to Amphibia only, but recent analyses put them as a sister clade to all crown tetrapods.

Temnospondyls

a very diverse radiation of tetrapods, from alligator-like salamanders to large, scaled, frog-like creatures. Cowens places these ancestral to Amphibia only, but recent analyses put them as a sister clade to all crown tetrapods.

Seymouriamorpha

Radiate in Permian

but earliest fossils from the Carboniferous... larvae have external gills, which pulls them out of the amniota...

- vertebrates


The Amniote Divide

The amniotic egg was a big advance

- amnion protects the embryo - yolk sac provides nourishment - allantoic sac holds waste produced by embryo

Resist desiccation

Provision embryo

allows for colonization of dry habitats

Primitive Amniotes

Hylonomus lyelli – an early reptile

Carboniferous of Nova Scotia

E. Carboniferous

- The Amniote Radiations

Anapsid ancestor

Hylonomus

Casineria

ANAPSID (turtles?)

DIAPSID

SYNAPSID

I. The Precambrian

- Vendian

II. Paleozoic






F. Permian (300-251 mya)


Pangaea forms

The fusion of land masses reduced the amount of humid coastline and increased the extent of dry inland areas. This favored the amniote radiations over "amphibian" clades.

F. Permian

- The Amniote Radiations Diversify

Anapsid ancestor

Hylonomus

ANAPSID (turtles)

DIAPSID

SYNAPSID


Synapsids dominate through the early Permian

Mammals

Cynodonts

Gorgonopsids

Therapsids

Pelycosaurs

Dicynodonts


Pelycosaurs dominate early

include the great sail-finned animals like Dimetrodon


Early Therapsids, like Gorgonopsids, dominate in the mid-late Permian

Dinocephalians

Moschops


Dicynodonts come to numerical dominance in the late Permian

abundant herbivores


and the first Cynodonts appear


large herbivorous anapsids were also present


Diapsids were small and lizard-like; the Synapsids ruled terrestrial communities


- Plants!!


- Plants!!

- the dry climate reduced the great Carboniferous swamp forests; lycopods shrink...

- Ferns, and gymnosperms ("seed ferns", Ginkos, Cycads, and Conifers) gain prominence...

- In particular Glossopteris - a seed fern - that produces seeds on its leaves like sori of ferns...

The evolution of gymnosperms introduced two important adaptive features:

- pollen (male gametophyte) - no more swimming sperm; reduced reliance on open water habitats

- seed - protective seed coat reduced desiccation of embryo, and nutritious endosperm provisioned the embryo with energy. (Like the amniote egg).


The great Permian extinction!!!!

A huge mantle plume rises towards the surface...



then it pops like a zit!!



A huge mantle plume rises towards the surface...

resulting in a great bubble of flowing lava... the Siberian flats (200,000 squ. mi)



- results:

90-95% of marine species go extinct...

trilobites

placoderms

acanthodians


- results:

90-95% of marine species go extinct...

trilobites

placoderms

acanthodians

70% of all land families

pelycosaurs

Documents

IV. Early Life