Diversity of life; geological control on biogeography; the fossil record

Jarðsaga 1

– Þróun Lífs og Lands –Ólafur Ingólfsson

The Diversity of Life

Biodiversity (fjölbreytileiki lífsins) is the totality of genes, species, and ecosystems

The wealth of life on Earth is the product of hundreds of millions of years of evolutionary history.

The Tree of Life

Relationshipsbetween taxa thatconstitute theArchaeobacteria(forngerlar), Eu-bacteria (raun-gerlar), Protists (frumdýr), Plants and Animals is not so straight fore-ward as we used to think...

The Six Kingdoms (ríki) of living things on Earth

The six kingdoms of life on Earth

YesMulticellular 500 million years agoPlantae

NoMulticellular700 million years agoAnimalia

NoUnicellular or Multicellular1 billion years agoFungi

(Sveppir)

SometimesUnicellular 1.5 billion years agoProtista(Frumdýr)

Eukaryotes:(Einkjörnungar)

NoUnicellular3 to 4 billion years agoArchaea

SometimesUnicellular3 to 4 billion years agoBacteria

Prokaryotes:(Dreifkjörnungar)

Photo-synthesisStructure When EvolvedKingdom

Number of species of living organisms

> 10 000 000~1 326 000Animalia>320 000~270 000Plantae>1 500 000~72 000Fungi>600 000~80 000Protista

>1 000 000~4 000ProkaryotesBacteria and Archaea

Total speciesNamed speciesKingdom

• Known total world species: ~ 1 752 000

• Estimated total world species: 10-100 million2/3rds of all animal species are insects - It is humbling to realize that

humans and other large animals are freakishly rare life forms, since 99% of all known animal species are smaller than bumble bees ...

Evolutionary trends through time:• Organisms evolve from simple to complex forms over time- Bacteria ⇨ protists ⇨ multicelluar organisms ⇨ plants and animals

• There is a general tendency for size toincrease during the evolution of a group of animals

• Evolution never goes in reverse, from complex to simple forms

Classification and evolution

Since Darwin's time, biological classification isunderstood to reflectevolutionary distances andrelationships betweenorganisms. The creatures of our time have had common ancestors in the past... they are members of the same family tree...

Carolus Linnaeus

(1707-1778)

Charles Darwin(1809-1882),

Adaptive radiation

The great diversity of life is largely a result of adaptiveradiation (aðlögunarkvíslun) = the diversification of a species as it adapts to different ecological niches and ultimately evolves into different species. Natural selection (náttúruval) is the principle mechanism driving adaptive radiation.

Animal phylogeny (þróunarferill)This structure grows as new species arise, each forming a new branch...

The Earth and all its contents have a very long history, during which they have devel-oped and become alter-ed: life has changed and diversified as it descended through myriad generations since its unique origins in the remote past, spreading across the globe as circumstances permitted.

Taxonomy• Taxonomy is the science of classifying organisms. The

Linnaean system breaks down organisms into seven major divisions, called taxa (singular: taxon; Ís: flokkunarheild). The divisions are as follows (Example: taxonomy of Man):

• Kingdom (ríki) animalia (dýr)• Phylum (fylking) chordata (seilýr); subphylum:

vertibrata (hryggdýr)• Class (flokkur) mammalia (spendýr); subclass:

eutheria (legkökuspendýr)• Order (ættbálkur) primate (prímati)• Family (ætt) hominidae (mannætt)• Genus (ættkvísl) homo (maður) • Species (tegund) sapiens (hinn viti borni maður)

Biogeography- The distribution and abundance of organisms intime and space on a broad geographical scale -

Boundary conditions in biogeography area defined bytemperature (solar energy and its distribution), precipitation

and the existance of physical barriers

Today´s biogeography reflects global distribution of energy...

Simplified model for global atmospheric circulation

Surface currents are generatedby stable wind systems

The Great OceanConveyor Belt

The most important ecosystems of the world

1. (light green) well-tempered rain forests, 2. evergreen boreal coniferous woods, 3. (green) tropical rain forests, 4. (dark green) summer-green deciduous forests, 5. (yellowish orange) tropical dry forests, 6. (orange) dry forests of temperate areas, 7. (light violet) thorny and succulent vegetation, 8. (violet) semi-deserts, 9. (dark violet) xeromorphic vegetation 10. (light blue) dry steppe, 11. dry savannah, 12. (blue) moist savannah, 12, 13. (dark blue) pasture, steppe, 14. (brown) deserts, 15. (white) tundra, 16. (grey) ice

Global biodiversity – vascular plants

Vegetation and climate

Iceland

Latitudional temperaturezones in the Oceans

Surface water zonation in the N Atlantic

...and biogeography also reflectsdevelopment of barriers through time

Examples of typesof barriers:

• Oceans and straits

• Mountain chains

• Continental scale glaciers

• Large deserts

• Large river canyons

Zoogeography is the study of geographical distribution of animals about the globe.

The Wallace Line

Alfred R.Wallace(1823 - 1913)

Alfred Russel Wallace was the now-almost-forgotten co-discoverer of thetheory of evolution. Darwin had pretty well formulated the theory when he learned that Wallace was about to publish a similar idea. When Wallace heard about Darwin, he politely stood aside and let Darwin publish first.

The Wallace Line is a major break in faunal composition

...east of it the fauna isAustralian, with kangaroos, wallabies and possums.

Java tiger

West of it, the fauna isrelated to mainland Asia, with its tigers, elephants and monkeys...

Macaque Monkey Cassovari Possum

Java rhino Kangaroo WallabyOrangutang

Why the Wallace Line?It marks the bondary between the Australian the Eurasian Plates

The take-home messages

• The wealth of life on Earth today isthe product of hundreds of millions of years of evolutionary history.

• The great diversity of life is largely a result of the diversification of a species as it adapts to different ecological niches and ultimately evolves into different species.

The take-home messages

• The development of ecological niches isover time controlled by large-scalegeological events (ocean spreading, mountain-building, opening and closing of straits etc)

• Today´s biogeography primarily reflectsglobal distribution of energy (which islargely controlled by continent configuration) and the geological development of barriers to spreading of organisms.

Earth History, Ch. 3 28

Fossils and the diversity of life

• Our knowledge of past life is derived mostly from fossils

• Fossil = the preserved remains or traces of a once living organism– Usually thousands or millions of years old

(if it still smells, it ain’t a fossil)

Fossils reflect evolution, andbiogeography of the past

The fossil record contains evi-dence of how life and environ-

ments have changed and evolved throughout the earth’s history.

What are Fossils?

• Fossils are the prehistoric remains ortraces of life which have been preserved by natural causes in the Earth's crust.

• Fossils include both the remains of organisms (bones or shells), the traces of organisms (tracks, trails, and burrows -called trace fossils), and chemical traces of ancient organisms (molecular fossils).

How to become a fossil...To be preserved as a fossil, an organism must:

• Have preservable parts. Hard parts (bones, shells, teeth, wood) have a much better chance at being preserved than do soft parts

• Be buried by sediment. Burial protects the organism from decay.

• Escape physical, chemical, and biologicaldestruction after burial. The remains of organisms could be destroyed by burrowing (bioturbation), dissolution, predation, metamorphism, or erosion.

There are several ways in whichfossils are preserved...

1. Unaltered preservation (Insects or plant parts trapped in amber) 2. Petrification (Rock-like minerals seep in slowly and replace the original organic tissues) 3. Replacement (An organism's hard parts dissolve and are replaced by other minerals) 4. Carbonization=coalification (Only the carbon remains in the specimen)5 Recrystalization (hard parts revert to more stableminerals or small crystals turn into larger crystals) 6. Authigenic preservation (molds and casts of organisms that have been destroyed or dissolved).

How likely is it that an organism is preserved as a fossil...

• There are >1,7 million living species today, probably >10 million.

• There are only about 250,000 known fossil species.

• The fossil record covers many hundreds of millions of years, andthe living flora and fauna represent only one "instant" in geologic time. Maybe >100.000.000 species have occurred through Earths history.

• If fossil preservation were common, the number of fossil species should far outnumber the number of living species.

•The fact that the number of fossil species is so small suggeststhat the preservation of organisms as fossils is extremely rare.

The noted paleontologist Stephen Jay Gould estimatesthat 99% of all plant and animal species that have existed have already become extinct with most leaving no fossils.

Why is fossil preservation so rare...1. Habitat – most plants and animals live ondry land, where the probability of becoming buried in sediments is small

2. Lack of hard parts - For soft parts of organisms to be preserved, it is necessaryto isolate them from oxygen almostimmediately after death. This most likely occurs when organisms are rapidly buried in fine-grained sediment in anoxic water; this only happens in rare environments.

3. The activities of the geological engines – sea floor is constantly destroyed by subduction; weathering and erosion destroys fossiliferous sedimentary rock.

Earth History, Ch. 3 35

Completeness of the fossil record

Scaveng-ing Decay

of softtissues

100%

Continuous removal of “potential” fossils

AbrasionAnd

transportBurial

FinalPreser-vation

Decreasing probability

Death

?%The probability of preservation depends on the anatomy and habitat of theorganism—marine organisms with hard parts are most likely to be preserved

William Smith1769-1839

English engineer and geologist who is best known for his development of the science of stratigraphy. He determined the succession of Englishstrata across the whole country, fromthe Carboniferous up to theCretaceous. He also established their fossil specimens and laid the foundations for faunal successions in biostratigraphy. Smith's geologic map of England and Wales (1815) set the style for modern geologic maps.

In 1819, hepublished a workentitled Strata identified by organized fossils.

Distribution of fossils• The distribution of fossils within Earth´s history is not random - fossils occur in a consistent order. This is true at a regional, and even a global scale.

• Fossil organisms are more unique than rock types, and much more varied, offering the potential for a much more precise subdivision of the stratigraphy and events within it.

Faunal Succession- stratigraphic ordering of fossil

assemblages (William Smith), which was the basis of worldwide correlation

Principle of faunal and floral succession

Dinosaurs

Flowering plants

Plesiosaurs

Everywhere in the world, trilobites are found lower in the stratigraphy than marine reptiles. Dinosaurs occur after the first occurrence of land plants.Ferns always found before the occurrence of flowering plants...

Ferns

FishesTrilobates

Index fossils

References and good web-sitesStanley, Earth System History, chapters 3, 4 and 7.

Fortey, R. Life, a natural history of the first four billion years of life on Earth. New York, Vintage Books, 346 pp.

http://fossils.valdosta.edu/index.html

http://fossils.valdosta.edu/index.html

http://www.ucmp.berkeley.edu/alllife/threedomains.html

http://www.palaeos.com/Default.htm

http://www.pbs.org/wgbh/evolution/library/index.html

http://www.fossilmuseum.net/Time%20Machine/Geologic_Time_Machine.htm

http://www.seaworld.org/just-for-teachers/guides/diversity-of-life/

http://www.palaeos.com/Kingdoms/default.htm

http://www.earth.uni.edu/~groves/EHCh03lecture.ppt

http://www.cartage.org.lb/en/themes/Sciences/Zoology/AboutZoology/DiversityLife/DiversityLife.htm

http://www.ucmp.berkeley.edu/index.html