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28 Cards in this Set
- Front
- Back
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most common ions dissolved in ocean
-sources? |
+ve: from weathering
magnesium, calcium, potassium, sodium -ve: from volcanoes (mid-oceanic ridge, subduction zones) chloride, sulfate, carbonate |
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two factors that control density of water
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salinity & ocean temperature
higher salinity, lower temperature --> denser water (bottom of the ocean: water is denser (has sunk/pressure of all the water above it), colder (--> density), saltier) |
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upwelling
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- upward flow of water in ocean
- brings cold, nutrient-rich water from ocean depths - occurs along western coasts of continents, in trade winds belts |
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thermohaline circulation
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- deep-sea currents driven by differences in water density
- cooler temperatures and rising salinity cause water to become dense and sink - as tropical surface water moves poleward and cools, it sinks - as surface water evaporates or freezes, seawater becomes saltier (salt doesn't evaporate, nor does it freeze in with the water) --> arctic, antarctic water is dense (sinks) |
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diversity in life
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result of reproduction with mistakes (mutations), natural selection favors certain mutations
machines imitate life in that they can evolve with mistakes as programs are copied |
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advent of life
oldest fossils |
4 bya
3.5 bya fossils of 1-cell (no nucleus) bacteria, algae ("prokaryotes") |
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eukaryotic cells
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1.5 bya
cells with nuclei, organelles (created by endosymbiossis - cell engulfs bacteria in surrounding environment) |
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soft bodied organisms
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1.0 bya
burrows of worms in mudstone but b/c they are soft-bodied, they decay easily and so don't leave good fossil records |
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hard bodied organisms
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540 mya
calcium carbonate shells developed as a mutation: too much calcium carbonate in bloodstream, precipitated outside body, natural selection favored more protected organism hard bodies evolved quickly |
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first fish
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500 mya
primitive vertebrate mutation prevented larvar from maturing 450 mya gill support bones in jawless fish fuse to form jawbone |
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first amphibians
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350 mya
- fish move to land - fins of stumpy-finned fish (who live on bottom of ocean and use stumpfins as "legs") --> legs - process of evolution takes 25 my |
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first reptiles
what was happening at the same time? sail back reptiles |
300 mya
- first organism totally free from the water: lay waterproof eggs (amniote eggs) that seal embryo at the same time: pangaea forming. continents colliding - land in middle of supercontinent previously uninhabited 275 mya mammal-like: chew food, generate body heat, fur (probably) - seal in body heat (adaptation!) |
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first mammals
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200 mya
warmblooded, fur (--> can exist in colder climates) mammals get increasingly smaller, which allows them to hide/escape from dinosaurs |
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dinosaurs
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dominant 225 mya - 65 mya
get larger and larger (while mammals get smaller and smaller, forced into nocturnality to protect themselves) some small dinosaurs evolve into birds - feather, bony tail, claws |
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early tree dwellers
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grasping hands, stereoscopic vision, larger brains
evolve during radiation of mammals - these are our ancestors |
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mass extinction at the KT boundary
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65 mya
KT boundary: calcium carbonate-producing fossils in K --> rocks are white. distinct boundary where rocks turn dark (no photosynthesizing organisms) |
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cause of KT extinction
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asteroid impact
asteroid: 10km diameter, crater: 100mi diameter clay layer between KT boundary - iridium rich (as are asteroids) chicxulub crater in yucatan peninsula |
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evidence of KT impact
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- iridium layer
- shocked quartz (criscrossing lines produced by high pressure impact/shock) - glass microspheres |
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causes of extinction
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firestorms: things coming back into atmosphere burst into flames upon entering atmosphere
"impact winter": dark and cold --> no photosynthesis |
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other mass extinctions
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mass extinctions occur about every 30 million years
250 mya: permian/triassic boundary - cause unknown (impact? volcanism?) - killed 96% of marine species, 75%-80% of all species |
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carbon cycle
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1. volcanoes emit CO2
2. rock weathering takes CO2 from atmosphere, erosion washes CO2 into ocean 3. marine organisms form shells, remove CO2 from ocean/atmosphere, shells and skeletons collect to form limestone 4. oceanic crust subducted - limestone that has accumulated heats up, releases CO2 in volcanic eruptions |
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negative feedback in the carbon cycle
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increased weathering when CO2 content is high, temperatures are warm
when CO2 ^ --> temp ^ --> faster weathering --> more CO2 in ocean --> more limestone (which subducts and is released by volcanism --> CO2 ^ |
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nitrogen and phosphorus
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1. nitrogen as it exists in the atmosphere cannot be used by plants; fixed into NO3 by nitrogen-fixing bacteria in soil
2. washed into ocean by erosion 3. phytoplankton in ocean feed on nitrates (nutrient) 4. dead phytoplankton/phytoplankton waste on floor accumulates, is subduction 5. ocean floor subducted, nitrogen comes out volcano phosphates do the same thing except they don't need to be fixed |
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long-term climate change
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10 degrees C variation from greenhouse periods (no glaciers) to icehouse periods (glaciers)
1. CO2 comes from volcanoes sooo PLATE TECTONICS DRIVES LT CLIMATE CHANGE 2. high sea levels -- deep sea currents transport heat 3. volume of volcanic rock 4. pulses of mantle convection |
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medium-term climate change
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5 degrees C variation between glacials and interglacials
100k years between. last glacial max 18k years ago; present interglacial 11k years caused by orbital cycles: eccentricity (100k years), precession - earth wobbles (23k years), tilt - changes a few degrees, affects solar radiation (41k years) |
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the importance of cool summers
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at high northern latitudes
cool summers --> snow does not melt, forms ice under pressure --> glaciers --> albedo ^ --> solar radiation reflected --> colder |
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short-term climate change
- solar activity - volcanic eruptions |
1-2 degrees variation
solar activity: sun gives off variant amounts of energy. every 11 years, there is an increase/decrease of sunspots volcanic eruptions: dust, aerosols are put into the atmosphere and reflect solar radiation CO2 levels rising from burning of fossil fuels (within last 30 years) 285 ppm - before industrial revolution 385 ppm - today 600 ppm - next 30 years |
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volcanic eruptions and global warming/cooling
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long-term: release CO2 (which is a greenhouse gas so it warms up the atmosphere)
short-term: release dust, aerosols, ash, which reflect solar radiation and cool the atmosphere |
