History of Life from Odovician
History of Life from Ordovician
Ordovician Period 488-443 mya
End of the Ordovician was one of the coldest times in Earth history
Marine Diversification
Ordovician - Major diversification of marine organisms: more niches filled!
End of Ordovician
Mass extinction may have been caused by drop in temperature and drop in sea level
Second largest extinction
Silurian Period (444-415 mya)
Gondwana drifts N
Sea level rises and ice sheets melt
Ammonoids
Gnathostomes
Marine vertebrates with jaws and fins
The colonization of land
Plants invaded land in the late Silurian/early Devonian, 408 Ma, probably in wet, transitional habitats
Silurian into Devonian
Devonian Period (416-358 mya)
Pangea starts to form
The colonization of land
Major hurdle: water loss
Key innovations at this time: vascular tissue, support tissue (no water to hold up body); spores, then seeds (with protective covering), for reproduction without water
The colonization of land
Earliest terrestrial animals were arthropods, in Devonian, with marine ancestors
Chelicerates: spiders, scorpions
Mandibulates: millipedes, springtails
Chelicerates
Mandibulates
Herbaceous, predatory, detritivores
Colonization of land
Terrestrial vertebrates arose in late Devonian
Amphibians, fed on arthropods in swampy (transitional) habitats
Although extant tetrapods have five (or fewer) digits, recent discoveries show that early amphibians had 7 or 8 digits
End of Devonian
Mass extinction marked end of Devonian
Carboniferous Period (354-290 mya)
Paleozoic oceans between Euramerica and Gondwana began to close, forming the Appalachian and Variscan mountains
Sea levels swing widely
The first forests
Diversification of seed ferns, gymnosperms, no flowering plants yet
First winged insects, including dragonflies with 70 cm wingspans!
The Amniote Egg
Amniotes include ‘reptiles’, birds, mammals; diverged late Carboniferous
Derived from amphibians
Amniote egg allowed terrestrial reproduction: a key innovation
Amniotes
Anapsida, Synapsida, Diapsida
Refers to skull openings: none, one, or two
Anapsids are turtles
Synapsids are “mammal-like reptiles”
Diapsids gave rise to lizards, archosauromorphs (crocs, dinosaurs)
Synapsids: ancestors to mammals
Permian Period (299-250 mya)
Vast deserts covered western Pangea during the Permian as reptiles spread across the face of the super continent
Permian Period
Insects, amphibians, and early reptiles in swamp forests
Permian extinction
Largest mass extinction (96% of species)
Lowest sea levels in history
Ammonites, stalked echinoderms, brachiopods reduced
Trilobites and many corals extinct
Extinctions on land less pronounced
The Mesozoic Era
Divided into three periods
Triassic
Jurassic
Cretaceous
Major geologic event was the breakup of Pangea
Pangea allowed land animals to migrate from the South Pole to the North Pole
Life began to rediversify after the great Permian extinction and warm-water faunas spread across TethysSea
Period of warm, mild climate
Mesozoic: the age of reptiles
Both marine and terrestrial forms
Land plants dominated by cycads and gymnosperms
Anatomically ‘advanced’ insect orders, including hymenoptera
Triassic Period (251-199 mya)
Seas repopulated after Permian extinction
First dinosaurs and mammals
Marine reptiles: Lepidosaurs
The Amazing Archosaurs
Pterosaurs: evolved true flight
Quetzalcoatlus
Wingspan 12 m
The Amazing Archosaurs
Ornithischia:
Hadrosaurs
Stegosaurs
The Amazing Archosaurs
Saurischia:
Tyrannosaurus rex
Apatosaurus
The Amazing Archosaurs
Birds: living archosaurs
End of Triassic
Mass extinction
Ammonoids and bivalves decimated
Jurassic Period (200-144 mya)
A wide Tethys ocean separated the northern continents from Gondwana
Continents break up by end of period
Jurassic Period
Radiation of the dinosaurs
Mesozoic marine revolution
Crabs
Bony fishes – telosts appear
Gastropods, bivalves and bryozoans rose to dominance
Mammals
Morganudoconts
Cretaceous Period (145-65 mya)
More continental movement
Cretaceous Period
Surviving dinosaurs diversify
Seedless plants and gymnosperms begin to decline
Rise of Flowering Plants
Radiation of the Angiosperms (125 Mya)
Early angiosperms (flowering plants) were non-woody, had a competitive advantage over gymnosperms (conifers, ginkgo)
Sauropods with long necks may have fed on tall conifers in Jurassic
Shorter Hadrosaurs in Cretaceous may have provided selection pressure that favored rapidly growing angiosperms
End of Cretaceous
Mass extinction
Only one surviving lineage of dinosaurs
K-T Asteroid Impact
Asteroid
Present Cenozoic Era
Two Periods
Tertiary Period
Quaternary Period
Seven Epochs
Tertiary Period (65 mya – 5 mya)
More continental movement
The adaptive radiation of the mammals
First appeared in Triassic, placental mammals and marsupials in late Creteceous, big radiation in the Tertiary
First mammals insectivorous or omnivorous; carnivory associated with diversification
Homeothermy, hair, milk = shared traits; most are viviparous
Mammal radiation
Three subclasses:
Prototheria (platypus, echidna: NOT viviparous)
Mammal radiation
Three subclasses:
Metatheria (marsupials)
Mammal radiation
Three subclasses:
Eutheria (placentals)
Mammal radiation
Sinapsids to therapsids to cynodonts to mammals
Mammal radiation
Major changes over time:
Cranial characters, probably for mobility and speed
Jaw characters, probably for subduing prey
All skeletal characters modified from those existing in ancestors
Mammal radiation
Phylogenetic relationships were difficult to resolve: radiation was fast
Mammal radiation
Angiosperm coevolution with insects
The flower as a key innovation
Synchronicity between adaptive radiation of hymenoptera and lepidoptera, and adaptive radiation of angiosperms, in Tertiary
Insect pollination more efficient than wind pollination
Angiosperm coevolution with insects
Coevolution between plants and insect herbivores also important
Resin canals, a defense, has evolved multiple times
Oligocene
Adaptive radiation of Poaceae
Quaternary Period (5 mya-present)
•The world has taken on a "modern" look, but note that Florida and parts of Asia were flooded by the sea
Pleistocene
The last expansion of the polar ice sheets took place about 18,000 years ago
Ice age
Sea levels dropped
70% of mollusc species became extinct
Global climate generally drier
Later Cenozoic
Climates became cooler and drier
Grasslands and woodlands dominated
Grazing and browsing animals thrived
Earth in ice age
Extinctions in Pleistocene
Shallow water marine invertebrates
Large bodied mammals and birds
Ground sloth
Giant bison
Saber tooth tiger
Current extinction
We are perhaps in the midst of another mass extinction
Earth today