31-1Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Chapter 31: Evolving earth

31-2Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

History of life on earth

• Fossils provide information about past life– preserved remains or indications of organisms

• Whole organisms or parts of organisms– shells, bones, leaves, pollen

• Tracks and traces– footprints, burrows

• Chemical fossils– organic compounds

31-3Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fossils• Organisms are preserved when they are protected

from decay– buried in sediment – encased in resin

• Compaction and chemical changes turn sediments into rock

• Depending on type of rock, fossils may – retain their shape– be flattened– be carbonised (soft parts preserved as a carbon film)– be filled in with minerals– dissolved out leaving an empty mould– replaced with other material, such as silica (opal)

31-4Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Time scales

• Rock layers (strata) contain characteristic sets (suites) of fossils

– rocks with the same suite of fossils are of the same age

• Fossils are used to divide the geological time scale into eras and periods

• Ages of rocks and fossils determined using radiometric dating

31-5Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fig. 31.5: Geologic time scale(based on the 2000 edition of the International Stratigraphic chart)

(cont.)

31-6Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fig. 31.5: Geologic time scale (cont.) (based on the 2000 edition of the International Stratigraphic chart)

Copyright © T Itoh & R M Brown Jr, Planta Journal, vol. 160, pp. 372–81. Springer-Verlag, 1984

31-7Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Eras

• Major divisions of geologic time– Precambrian ( 4 500–545 m.y.a.)– Palaeozoic (545–250 m.y.a.)– Mesozoic (250–65 m.y.a.)– Cenozoic (65–0 m.y.a.)

• Divided into periods

31-8Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Precambrian Era

• Archean eon (4 500–2 500 m.y.a.)• Proterozoic eon (2 500–545 m.y.a.)• Oldest fossils 3 500–3 300 m.y.a.

– prokaryotes: cyanobacteria (including stromatolites)

• Photosynthesis released oxygen into atmosphere– changed composition of atmosphere– 2 300–1 800 m.y.a.

31-9Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Eukaryotes

• Prokaryotes only form of life for 2 100 m.y.• Oldest eukaryote fossils 1 400 m.y.a.

– single-celled protists with chloroplasts

• Multicelled organisms– metaphytes (red algae) 1 260–950 m.y.a.– animals 680–640 m.y.a.

31-10Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Ediacaran fauna

• Fossils of soft-bodied animals– impressions– tracks and burrows– no hard exo- or endoskeletons

• Difficult to classify some fossils– do not resemble living phyla

• Fossils first recorded from Ediacara Hills, South Australia

– fauna on all continents

31-11Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Palaeozoic era

• ‘Ancient life’ (545–250 m.y.a.)• Aquatic groups

– trilobites– brachiopods– nautiloids, ammonoids (cephalopod molluscs)– jawless and jawed fish (‘Age of Fish’)

(cont.)

31-12Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Palaeozoic era (cont.)

• Life moves onto land in Silurian period– arthropods– amphibians– reptiles– land plants

• Ended with mass extinction– Permian period (250 m.y.a.)– trilobites, many invertebrate groups

31-13Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Mesozoic

• ‘Middle life’ (250—65 m.y.a.)• Plants and invertebrates

– ferns, conifers, cycads– flowering plants– bivalves, predatory gastropods– ammonoids– reef-building corals

(cont.)

31-14Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Mesozoic (cont.)

• Vertebrates– mammal-like reptiles, dinosaurs, marine reptiles, flying

reptiles (‘Age of Reptiles’)– birds– mammals

• Ended with mass extinction– K-T boundary– ammonites (shelled cephalopods), many large reptiles

31-15Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Cenozoic

• ‘Modern life’ (65—0 m.y.a.)• Major groups

– mammals diversify (‘Age of Mammals’)– hominids– modern forms of most organisms

31-16Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Biogeography

• Biogeographic regions– areas of the earth occupied by characteristic biota

Terrestrial MarinePalaearctic Arctic/Antarctic

Oriental Cool temperate

Ethiopian Warm temperate

Australian Tropical

Nearctic

Neotropical

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Fig. 31.20: Biogeographic regions

31-18Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

‘New World’• Nearctic

– North America, Greenland– examples:

kangaroo rat pronghorn turkey

• Neotropical– South America, Central America– examples:

New World monkeys sloth rhea

31-19Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

‘Old World’

• Palaearctic– Europe, Asia– examples:

desman saiga

• Ethiopian– Africa, Madagascar, Arabia– examples:

hippopotamus giraffe and okapi lemurs (Madagascar)

(cont.)

31-20Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

‘Old World’ (cont.)• Oriental

– India, South-East Asia– examples:

tree shrew gibbon leafbird

• Australian– Australia and adjacent areas– examples:

echidna, platypus kangaroo emu

31-21Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Australian region

• More than Australia– New Zealand, islands of Western Pacific, New Guinea,

eastern Indonesia archipelago– biota determined by history and proximity

• Wallace’s Line– boundary between Australian and Oriental biogeographic

regions Oriental biota dominates to west, Australian biota to east

– approximates collision zone between tectonic plates

31-22Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fig. B31.5: Wallace’s Line

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Plate tectonics

• Earth’s surface formed from mobile plates– tectonic plates

• Move relative to one another– plate tectonics – continental drift

• Configuration of land masses have changed over geologic time

– still changing

31-24Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fig. 31.6: Distribution of plates

31-25Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Sea floor spreading

• Plate movement driven by sea-floor spreading• Lava rises from mantle to surface at oceanic

ridges– forms new oceanic crust on either side

• Continents pushed away from oceanic ridges– example: Indian–Antarctic ridge in Southern Ocean

separating Australian and Antarctic plates

31-26Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Subduction zones

• Where edges of plates meet• One plate slides beneath the other into mantle

– subduction zone– deep water trenches– examples: Marianas Trench, Java Trench

• Plates slide past each other– major fault zones– example: San Andreas Fault

31-27Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Fig. 31.7: Cross-section of lithosphere

31-28Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint

Ancient earth

• Movement of continents over geologic time• Land masses accreted into different configurations

at different times– Gondwana

southern masses

– Laurasia northern masses

– Pangea southern + northern land masses