ISP 203A Geological Times and Evolution Feb 28th – Flashcards

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First conclusive and successful (ie with modern living descendants today) form of complex life appear in the oceans at 540 Ma (millions of years) ago, and shortly thereafter

Common point between all groups described so far: they are invertebrates Many other complex forms of invertebrate sea life appear during the Cambrian: MOLLUSCA, ECHINODERMS (starfish, sea urchins, crinoids - sea lilies - among echinoderms still existing today) Animals also known as VERTEBRATES also first appear during the Cambrian; they have (like all vertebrates) a central nervous system in a brain, and a spinal cord that branches out from the brain. These remain relatively scarce and with relatively few species until later. Overall, a relatively short period, that lasts until ~490 Ma (will last for 50 Ma starting at 540 Ma)

all animals with a back bone, including fish, amphibians, reptiles, birds, mammals, will appear 'soon'

~490 million years ago. This major change in life diversity defines a new period: the Ordovician. Fish from that period are now extinct. Invertebrates that appeared in the Cambrian are still present but there is increased competition from fish (ancient placoderma fish) extinct

Quite abruptly, about 444 Ma ago In the fossil record, we observe a great loss of diversity in invertebrates, particularly these forms of life that are fixed to the bottom and do not move (fish who could swim appear to survive relatively well) This type of event named MASS EXTINCTION New species will gradually appear as the surviving ones diversify, this defines a new period Life still restricted to the oceans

Throughout the Silurian, fish has become very diverse, and very abundant throughout the ocean. This will continue throughout a new period, the Devonian We now have life on continents! Plants have appeared on land (until then, they would only restricted to sea) and so did invertebrates (notably arthropods, incl. insects) First abundant and diverse complex life on land. Major landmark Despite this, the Devonian period is also nicknamed the AGE OF FISH Important period as some fish started to have fins developing into 4 limbs, which will eventually form legs (nine fish, Australia)

some fish will acquire a more complex skeleton, with 4 legs they have the ability to walk, and eventually, they will venture out of the water

(or four-legged vertebrates) are everywhere today (all amphibians, reptiles, birds, mammals) This takes place during the DEVONIAN

Yet all amphibians need to live near water: they do not breather through lungs, they lay eggs in water, their young (larvae) live in water

The Devonian was possibly one of the most important period for history of modern forms of life (plants, fish, tetrapods) This will come to an end 359 Ma ago: abrupt changes are observed in the fossil record of sea life (not so much on land), again with loss of diversity of species A second MASS EXTINCTION just happened

Appears to have had a warm and wet climate, as suggested by evidence for marshes and tall dense forests during this period. These forests now preserved as fossils, and COAL Nicknamed the 'age of the amphibians' as these vertebrates had survived the Devonian mass extinction quite well will get very diverse and now will dominate land animal life lasts until ~299 Ma ago Some criteria allow to subdivide it further into the Mississippian and Pennsylvania (let's not worry about this and why) Most of our coal originates from remains from Carboniferous plants

The last period of the Paleozoic Amphibians now face some competition from other rapidly diversifying groups of land vertebrates: the AMNIOTES. These, unlike amphibians, can live and lay eggs totally outside of water Amniotes includes all mammals and all reptilians (reptilians currently living today: birds, lizards, snakes, crocodiles, turtles) The advantage that amniotes have over amphibians to not depend on water to lay eggs leads to a rapid loss of amphibians' population and diversity (although amphibians will never get extinct, some indeed still exist today, eg, frogs)

Very large amniote vertebrates replace once-reigning large amphibians (now extinct) Dimetrodon is the most common, most famous of these large animals from that period It is not a reptilian (therefore not a dinosaur), rather it is related to present-day mammals

Plate tectonics are known to have been operating during all of the Paleozoic and even before during the proterozoic, with uninterrupted continent break-ups, ocean spreading at mid-ocean ridges, subduction, collision, etc... During the Permian, 2 large continents just collided, forming a very long mountain range (the Appalachians are one part of that mountain range) all continents are assembled into one, called Pangaea This unlikely situation with all continents assembled into one leads into very harsh, arid, climate on this giant mass of land, where influence of ocean is minimal. This is a struggle for many forms of land life. Land life in the Permian overall does not perform very well, but the fossil record does who some mammals and reptilians, the descendants of which will later reign over continents

several continents and oceans

one continent (Pangaea) and one ocean (Panthalassa)

The LARGEST KNOWN FLOOD BASALTS (in Siberia) over rapid geological timescales (<1 million of years) Major climate change with severe global cooling The third and largest mass extinction, that affects both sea and land species. Many of the invertebrate groups that appeared during the Cambrian get completely extinct

After much life is "wiped out" the Earth is a whole new territory to be settled by the few forms of life that survived (in oceans and continents) A new 'explosion' of life, during a long time period called the Triassic (the first period of the Mesozoic) In oceans, a group of mollusks that survived the mass extinction will dominate and become very diverse: the AMMONITES

Many amniotes survive the mass extinction (most do not, including Dimetrodon) Among amniotes, reptilians will become the most abundant, diverse of these new land animals Today reptilians include all turtles, lizards, snakes, crocodilians and birds Reptiles will diversify during the Triassic: modern turtles ancestors, crocodilians, modern lizards' ancestors all appeared during this period of time

one new frontier for life, never explored before, the air (flight) -Some reptilians will achieve this as their fore limbs get long and light weighted, holding large membranes capable of supporting them in the air, i.e, flying : the PTEROSAURS (group now extinct)

Will become very successful and diverse, will rapidly dominate over other forms of reptilians and other vertebrates in general A 4th mass extinction marks the end of the Triassic and the beginning of new period: the Jurassic On land, many groups disappear and leave unoccupied niche for dinosaurs to thrive and diversify

Dinosaurs did dominate land animal life during the Jurassic, yet most dinosaurs portrayed in the Jurassic Park movies lives more recently, during the next period: the Cretaceous

Ceratopians: large herbivores. Triceratops and many others...

Stegosaurians: large herbivores. Will disappear during the Cretaceous. Stegosaurus is their most famous representative.

Theropods: some were meat eaters, other herbivores. Bipedal Also a very diverse group Include Allosaurus and Tyrannosaurus (T. rex)

some were meat eaters, other herbivores. Bipedal Also a very diverse group Include allosaurus and tyrannosaurus (T. rex)

some were meat eaters, other herbivores. Bipedal Include the AVIAN DINOSAURS, a group of small bipedal meat-eater dinosaurs Some of them had feathers (notably Velociraptor) Avian dinosaurs are the ancestors of present BIRDS

The 5th mass extinction: end of the Mesozoic, end of the 'age of dinosaurs' -Geological history is somewhat repetitive -Like other dominating forms of life before them, dinosaurs eventually will become extinct during A MASS EXTINCTION -Dinosaurs were so dominant that their extinction dramatically changes life on Earth; a new era is defined -This is our era: THE CENOZOIC, OR TERTIARY -mass extinction happens 65.5 million years ago -Again,evidence for FLOOD BASALTS (see the Deccan traps in India from last week lecture) -Coupled with a large meteor impacting the Earth (in what is the present-day Yucatan peninsula, on the Caribbean coast of Mexico) -In oceans, rate of extinction is also massive: AMMONITES get extinct also

Cenozoic nicknamed the 'age of mammals' Mammals are known to have existed since the late Paleozoic (Permian, and maybe earlier) They are known as sparse fossils throughout the whole Mesozoic -At all times, they were small animals (rodent-sized at the most), with little diversity, mammals would typically be living near and under the ground -Competition for food and living spaces with dinosaurs at all times is fierce and never turns at the advantage of mammals -Until dinosaurs get extinct...at which stage, competition is eliminated, and mammals take over the niches left by now-extinct dinosaurs -Rapidly evolving with large herbivores, large predators, etc... -Groups of modern mammals appear gradually throughout the Cenozoic. Some get extinct and other groups take over

Meanwhile... A group of small flying dinosaurs (the avian dinosaurs), that appeared gradually during the Cretaceous period had a few species surviving the 5th mass extinction As mammals will expand and diversify on land, birds will expand and diversity in air. Their diversity and abundance throughout the Cenozoic rivals that of mammals Without that small number of surviving avian dinosaurs surviving the mass extinction 65.5 million years ago, birds would not exist today

65.5 million years ago was bad for life on Earth... a mass extinction event. The last major one Cenozoic animal life (on land) mostly diversified from 2 small groups --> MAMMALS --> Some very small flying avian dinosaurs, also known as BIRDS --> MAMMALS and BIRDS will rapidly dominate the Cenozoic habitats Cenozoic also known as the "AGE OF MAMMALS" Cenozoic lasts until today: we are still in the Cenozoic

For most of its duration, it is a warm era (so were the Creaceous and Jurassic beforehand) During the Eocene (one of the periods that subdivide the Cenozoic), there is a thermal maximum. ~ 50 million years ago During the Cenozoic, most of today's tallest mountain ranges form: Rocky Mountains. Alps - Balkans - Himalayas. (action of plate tectonics)

Long E-W collision mountain ranges form, and N of the Himalayas, the Tibetan plateau is uplifted Climate through the Cenozoic progressively gets cooler This may be a consequence of the Tibetan plateau uplift, diverting westerlies wind trajectories

Late Cenozoic, very recently in the geological times: ~ 2 million years ago: major climate change events will take place, the Earth will get cooler The ICE AGES Succession of cold periods with large continental ice caps and warm periods with few ice caps Cold periods called GLACIATIONS. Warm periods are INTERGLACIAL

end of the ordovician period: 444 million years (Ma) ago end of the Devonian period: 394 Ma ago END OF THE PERMIAN PERIOD (AND OF THE PALEOZOIC ERA): 250 MA AGO (the main one _see the Siberian flood basalts) End of the Triassic period: 208 Ma ago END OF THE CRETACEOUS PERIOD (AND OF THE CENOZOIC ERA): 65.5 MA AGO (the most famous one_ causes: flood basalts and a meteorite_)

vertical axis, the eras and periods (abbreviated, Cmb= cambrian, Crb =carboniferous, otherwise the first 3 letters of the periods) horizontal axis shows the evolution of different vertebrate classes, and the period during which they branched out from a common ancestor Example: amphibians and amniotes branch out from a common ancestor at the beginning of the carboniferous Thickness of the vertical bar (that may change over time) represent the known number of species in one group relative to another

these jawed fish classes are now extinct fish left side tetrapods right side (frog, salamander, bird, rodents) amphibians (frogs) amniotes (salamander, bird, rodents) Note that it is correct to say that (for instance) mammals are also amniotes, are also tetrapods, and are also vertebrates