What are two possible fates of plant material not eaten by animals?
It can be buried or decay. The latter requires oxygen
What is a negative feedback? What is a positive feedback? Give an example of each.
A negative feedback is a consequence of some change that retards that change. A positive feedback is a consequence of some change that accelerates that change.
How can carbon isotopes in limestone provide evidence about the history of atmospheric oxygen?
High values of carbon 13 in limestones indicate that large volumes of carbon accumulated rapidly. By measuring the relative percentage of carbon 13 in limestones of various ages, we can tell when these rapid accumulations occurred. Because an increase in
Draw sketches illustrating how increased burial of carbon reduces the atmospheric reservoir of Co2 and enlarges the atmospheric reservoir of O2
Burial (as opposed to decomposition) reduces the atmospheric reservoir of CO2 because since the plant did not decompose, it did not release its carbon. Instead that carbon is buried with the plant. Conversely, since the plant does not undergo decompositio
In what kinds of marine environments can carbon be buried in large quantities?
Organic carbon can be buried in large quantities in anoxic marine environments. The lack of oxygen means an absence of bacteria that would decompose the organic material.
Draw a diagram depicting the cycle of oxidized carbon that includes limestone, atmospheric Co2, and weathering
Bicarbonate forms through weathering (carbonic acid through rain percolates into less dense rocks) and is carried to the ocean, where it can accumulate offshore or in shallow water. Metamorphism of these sediments releases CO2, which completes the cycle b
Why are pelagic carbonates more likely than shallow-water carbonates to melt and return Co2 to the atmosphere?
Pelagic carbonates are easily destroyed by subduction along trenches near their place or origin. Shallow-water carbonates release their carbon dioxide only if they are caught up in mountain building.
How do glaciers promote chemical weathering?
Glaciers grind up the underlying rock by moving over mountains, which increases the surface area of rock exposed to weathering, which then releases marine carbon sediments which remain in shallow-water carbonate sediments for many years.
Why does the influence of moist climates on vegetation accelerate weathering?
Moist climates allow forests to occupy the land, and their roots accelerate chemical weathering because they secrete acids and other compounds that break down minerals. Forests also cycle water through the soil repeatedly, which results in the rapid disso
What can the study of oxygen isotopes tell us about ancient oceans?
The study of oxygen isotopes can tell us about changes in ocean temperature, salinity, and volume of glacial ice.
summarize how burial of organic carbon, alterations of carbonates at high temperatures, and changes in rates of weathering alter greenhouse warming by Earth's atmosphere
Burial of organic carbon sequesters carbon and increases oxygen composition reducing greenhouse warming, alterations of carbonates at high temperatures releases CO2 into the atmosphere increasing greenhouse warming,and if weathering increases then greenho
What kinds of geologic evidence suggest that continental glaciers spread widely more than 2 billion years ago?
Evidence of early Proterozoic glaciation includes well-laminated mudstones composed of varves that formed in the standing water of a lake or ocean in front of glaciers; the presence within mudstones of dropstones (pebbles and cobbles that appear to have f
What is curious about the Neoproterozoic rocks known as cap carbonates (hint refer to Earth System Shift 12-1)
It's been suggested that 'snowball earth' happened 750 and 635M years ago, when the sun's radiation was 6% less powerful, and land - clustered in one mass - was at high latitudes. The formation of glaciers created a positive feedback (high albedo). Cap ca
Life underwent extraordinary changes in the course of Proterozoic time. Using visual overview on 264-265, describe these changes and explain how some may have been related to changes in chemistry of the atmosphere
the rate at which the concentration of oxygen in Earth's atmosphere rose during the proterozoic eon had important implications for animal evolution; the limiting factor is the rate of diffusion of oxygen from the exterior to the interior of the organism
A
Why do geologists know more about the life that colonizes early Paleozoic seafloors than about the life that floated and swam above these seafloors?
Because seafloor dwellers left an extensive fossil record in the seafloor sediment, both skeletal fossils and trace fossils such as burrows
What fossil evidence suggests that distinctive new kinds of predatory animals evolved during Cambrian time?
The presence of several kinds of teeth in the Tommotian fauna indicates that a variety of small predators were present in the Early Cambrian. Evidence for new predatory animals during the Cambrian has also been found in an unusually well preserved Early C
What evidence is there that the variety of animals that burrowed in marine sediments increased during early Paleozoic time?
The base of the Cambrian is defined by burrows of complex form -- an index fossil whose first occurrence has been designated as marking the base of the Cambrian system, is a branched form reflecting an increase in behavioral complexity
Treptichnus pedum
T
What evidence is there that plants may have invaded the land before the end of the Ordovician Period?
Evidence that plants might have invaded the land before the end of the Ordovician Period consists of fossilized sheets of cells similar to those that cover the surfaces of modern land plants, as well as structures that resemble the spores released by prim
10. What evidence is there of a decline in the concentration of atmospheric carbon dioxide during Devonian time? (hint refer to figure 10-9A and Earth system shift 2)
Carbon isotope analysis of the carbon 13 content of limestone sediments provides evidence that that there was an increase in the rate of carbon burial during the Devonian. This results in an increase of atmospheric oxygen and a decrease of atmospheric car
Earth System Shift 14-1 (328-329) - Plants alter landscapes and allow vertebrates to conquer the land
During the Devonian period, plants had more extensive invasion on land, causing:
Stabilization of soil against erosion - roots gripped the soil and held it in place. While precambrian and early paleozoic rocks have braided-stream deposits, reflecting rapi
Earth System Shift 14-2 (334-335) - Expansion of plants causes global climatic change, glaciation, and mass extinction
Tree roots and associated fungi release chemicals that weather rocky soil, reducing the concentration of CO2 in the atmosphere (weathering consumes atmospheric CO2), weakening the greenhouse effect and cooling global climates.
Tillites reveal that contine
5. How did the history of glacial activity in Late Carboniferous time relate to the deposition of coal?
Cycles of falling and rising sea level corresponded to cycles of glacial expansion and contraction during the Late Carboniferous. As sea level rose and fell, it created cyclothems of coal deposition. A transgression resulted in the deposition of marginal
Earth System Shift 15-1 (352-353) - Weakened greenhouse warming results in great ice age
Expansion of glaciers in the southern hemisphere during the mid-Carboniferous period caused a dramatic drop in sea level
Climates at mid and high latitudes became colder and more seasonal - more like today - as evidenced by tree rings, which vary in size
Earth System Shift 15-2 (359-361) - The most destructive of all mass extinctions ends the Paleozoic era
The terminal Permian mass extinction wiped out 80-85% of all species, though total number of taxa eliminated was smaller because of the previous mass extinction 9 million years earlier.
The first - Guadalupian - mass extinction destroyed the organic reef
Earth System Shift 16-2 (394-395) - Volcanism and mass extinction
End of the Triassic period - conodonts and placodont reptiles died out, most bivalves, ammonoids, plesiosaurs, and ichthyosaurs were also lost, though recovered in Jurassic time. Few therapsid or large amphibian species survived on land, but dinosaurs sur
What conditions may account for the formation of widespread black shales in seas that spread over continental surfaces at certain times during the Cretaceous Period?
The black shales accumulated because of unusually poor circulation within the ocean and stagnation within the water column. When these waters spilled over from oceanic areas into shallow seas, black muds were deposited in epicontinental areas.
What evidence is there that an asteroid struck Earth at the end of the Cretaceous Period?
Evidence that a meteor struck Earth at the end of the Cretaceous Period includes abnormally high concentrations of iridium at the level of the Cretaceous-Paleogene boundary; "shocked" quartz grains at the same level; microspherules at the same level; micr
Major physical and chemical events altered life during an at the very end of the Cretaceous Period. Using the Visual Overview on 404-405 and what you have learned, describe these events and their consequences
Early Events
Sea level falling -
Sea level rising -
Widespread deposition of black shale -
Gondwanaland breaks apart -
Late events
High rates of seafloor spreading elevate sea level and lower the Mg2+/Ca2+ ratio of seawater -
Widespread deposition of chal
What groups of animals that played important roles in Late Cretaceous ecosystems were absent from the Paleocene world?
Animals that played important roles in the Late Cretaceous ecosystems but were absent in the Paleocene include rudists, ammonoids, giant swimming reptiles, and dinosaurs.
Which group changed more from the beginning of the Paleogene Epoch to the end - marine or land animals? Explain your answer.
Terrestrial animals changed more than marine animals. The marine life that remained after the terminal Cretaceous extinction closely resembled marine taxa of Late Cretaceous age, with only a few new organisms (such as whales) appearing in the Paleogene. I
What seems to have prevented corals from forming massive reefs before Oligocene time?
The magnesium-calcium ratio in the oceans, which did not reach a high level until the Oligocene, apparently prevented the aragonitic corals from forming massive reefs until the Oligocene.
Which animals took the place of large Mesozoic reptiles in Paleogene oceans?
Whales and sharks replaced Mesozoic reptiles in Paleogene oceans.
How does the fossil record of flowering plants reveal climatic change during Paleogene time?
The proportion of species within an angiosperm flora that have leaves with smooth margins is higher when the mean annual temperature is higher. During cooler periods, more species have leaves with jagged margins.
What happened to the deep sea at the end of the Paleocene Epoch?
At the end of the Paleocene, the deep sea warmed several degrees. The warming ended the downward flow of cool polar waters, reducing the levels of oxygen in the deep ocean. As a result, more than 70 percent of the deep-sea foraminifera species died out.
How did changes in patterns of oceanic circulation bring about glaciation in Antarctica?
In middle Eocene time, warm currents from the southern oceans warmed Antarctica. By early Oligocene time, South America and Australia had moved far enough from Antarctica to allow waters from the southern oceans to become trapped in a current around Antar
What is the origin of the geologic features that intrigue tourists at Yellowstone NAtional Park?
Yellowstone represents a hot spot where heating and igneous activity occur within the crust. The continuing igneous activity produces the geysers and hot springs that draw tourists to the area.
What factors influenced the isotopic composition of oxygen in skeletons of marine organisms during the modern Ice Age?
Factors that caused fluctuations in the oxygen isotope ratio in skeletons of Pleistocene marine organisms include the expansion and contraction of glaciers and an increase in the salinity of ocean water to the east of the Isthmus of Panama after it was up
What changes in the geographic distribution of land animals did the uplift of the Isthmus of Panama produce?
Before the Isthmus of Panama formed, a few species of mammals had passed between North and South America, but the terrestrial faunas of the two continents had remained largely separate. After the isthmus was uplifted, creating a land bridge, there was a g
How has climate change altered the general distribution of terrestrial vegetation since early in Pliocene time?
The alternations of glacial maxima and minima since the Pliocene have caused climatic belts and the floras that occupy them to shift over distances of hundreds of kilometers. Studies of the distribution of fossil pollen has shown that whole floras have no
What evidence is there that about 7 million years ago a major change occurred in the kinds of grasses that populate the world? How did this change affect animals?
Evidence of a major change in the kind of grasses that formed grasslands about 7 million years ago comes from analyses of ancient grassland soils and the teeth of the herbivores that grazed on them. These analyses reveal that there was a pronounced shift
How did members of the genus Australopithecus differ from modern humans?
Australopithecus had a relatively small brain and its skull was more like that of an ape than like that of a human; it was much shorter than an average modern human; although it walked upright, its long arms, strong wrists, and long, curved fingers and to
How did the great lakes form?
The retreat of ice from the last glacial maximum (retreated ~10,000 years ago) carved out basins in the earth's crust that were then filled by the meltwater as the ice sheet retreated
How does fossil pollen indicate that modern plant communities are temporary associations of species?
It shows that an evergreen forest unlike any other modern flora existed in the climate to the South of ice sheets - different species (and their relative pollens) have shifted their ranges independently, showing that they do not need to evolve in tandem w
How do fossil corals record Holocene sea level changes?
The moosehorn, or acropora palmata, always grows close to sea level, and can be dated by the uranium thorium method, indicating sea level in relation to the island for various past intervals. Colonies that grew during glacial minima are now above sea leve
What kinds of large mammals disappeared from North America ~12,900 years ago?
Elephants, giant beavers, 5 species of horse, 3 deer, 2 oxen, camels, short-faced bear, giant beavers, some others - about 35 species in all
When did the Younger Dryas begin and the Clovis culture collapse relative to the time when the large mammals disappeared
Evidence favoring the idea that climate caused the extinction of large mammals includes the fact that the Younger Dryas interval began and ended suddenly and temperatures shifted abruptly; and certain habitats that had supported many large herbivores disa
How does glacial ice in Greenland that is thousands of years old provide a record of climate change?
The relative level of O18 in the ice record reflects the temperature at the time of its formation - a higher ratio reflects a greater temperature.
When the climate warmed and evaporation from warmer seas provided more moisture, snow accumulated more rapid
Why is it not surprising that agriculture spread from the Middle east to Europe, rather than in the opposite direction?
While there is no evidence that climatic changes guided the initial expansion of agriculture, it couldn't spread until the glacial and near-glacial climates of Europe before the hypsithermal interval gave way to temperate climates that could support agric
What evidence is there that at times during the last 10,000 years climates in many areas have been drier than they are today?
Growth rings of pine trees - they're larger when climate is moister, smaller when drier, and have varied over time. Oldest trees are ~3400 years.
Fossil records of pollens and certain species reflect climatic shifts
Fossils of lake-dwelling life and polle
What conditions have affected relative sea level in particular regions during the past 7000 years, since global sea level approached its present condition?
The enormous weight of glaciers depressed the continental lithosphere, which has been rebounding ever since, thus some coastlines of the North Atlantic (Scotland, Scandinavia) are still rising and seas are regressing
In some areas, earth's surface is subs
What positive feedbacks might amplify climatic change in the near future in ways that should have modern humans concerned?
Sea ice in the Arctic Ocean shrank from 1980-2000. Some predict that the sea ice produced in winter could melt entirely in the summer, as opposed to partially today. Summer melting takes up most of the heat now - if it ceased, heat would warm the Arctic o