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Science Fair Project Ideas, Answers, & Tools
There have been other proximate causes of our current ice age, beginning with around 40 mya, and when the land bridge formed between the Americas around three mya , and are responsible for the "wobble" of advancing and retreating ice sheets in the Northern Hemisphere during this ice age. There is always the battle of the hypotheses in scientific circles, but the nearly universal consensus is that greenhouse gases, oceanic currents (with a land mass at the South Pole, and the landlocked North Pole), and Milankovitch cycle dynamics, in that ranking of importance, have caused the current ice age. Until the rise of humanity, the primary carbon dioxide input into the carbon cycle was via volcanism, which is related to tectonic plate movements, and plate movements also affected oceanic currents. Scientists are continually surprised by the dynamics and extent of Global Warming, and usually an unpleasant surprise, such as the findings published in 2014 which show that the Antarctic ice sheets are melting faster than expected, and in unexpected ways, and the Greenland ice sheet is also yielding alarming surprises.
But the branch of the that readers might find most interesting led to humans. Humans are in the phylum, and the last common ancestor that founded the Chordata phylum is still a mystery and understandably a source of controversy. Was our ancestor a ? A ? Peter Ward made the case, as have others for a long time, that it was the sea squirt, also called a tunicate, which in its larval stage resembles a fish. The nerve cord in most bilaterally symmetric animals runs below the belly, not above it, and a sea squirt that never grew up may have been our direct ancestor. Adult tunicates are also highly adapted to extracting oxygen from water, even too much so, with only about 10% of today’s available oxygen extracted in tunicate respiration. It may mean that tunicates adapted to low oxygen conditions early on. Ward’s respiration hypothesis, which makes the case that adapting to low oxygen conditions was an evolutionary spur for animals, will repeatedly reappear in this essay, as will . Ward’s hypothesis may be proven wrong or will not have the key influence that he attributes to it, but it also has plenty going for it. The idea that fluctuating oxygen levels impacted animal evolution has been gaining support in recent years, particularly in light of recent reconstructions of oxygen levels in the eon of complex life, called and , which have yielded broadly similar results, but their variances mean that much more work needs to be performed before on the can be done, if it ever can be. Ward’s basic hypotheses is that when oxygen levels are high, ecosystems are diverse and life is an easy proposition; when oxygen levels are low, animals adapted to high oxygen levels go extinct and the survivors are adapted to low oxygen with body plan changes, and their adaptations helped them dominate after the extinctions. The has a pretty wide range of potential error, particularly in the early years, and it also tracked atmospheric carbon dioxide levels. The challenges to the validity of a model based on data with such a wide range of error are understandable. But some broad trends are unmistakable, as it is with other models, some of which are generally declining carbon dioxide levels, some huge oxygen spikes, and the generally relationship between oxygen and carbon dioxide levels, which a geochemist would expect. The high carbon dioxide level during the Cambrian, of at least 4,000 PPM (the "RCO2" in the below graphic is a ratio of the calculated CO2 levels to today's levels), is what scientists think made the times so hot. (Permission: Peter Ward, June 2014)
Lead toxicity in plants - SciELO
Golisz, A., M. Sugano, S. Hiradate, and Y. Fujii. 2011. "Microarray Analysis of Arabidopsis Plants in Response to Allelochemical L-DOPA." Planta 233: 231–240.
Ni, G. Y., P. Zhao, Q. Q. Huang, Y. P. Hou, C. M. Zhou, Q. P. Cao, and S. L. Peng. 2012. "Exploring the Novel Weapons Hypothesis with Invasive Plant Species in China." Allelopathy Journal 29: 199–213.
Control of Red Algae in the Freshwater Aquarium
Canfield’s original hypothesis, which seems largely valid today, is that the deep oceans were not oxygenated until the Ediacaran Period, which followed the Cryogenian; the process did not begin until about 580 mya and first completed about 560 mya. The wildest swing in Earth’s entire geological record begins about 575 mya and ends about 550 mya, and is called the Shuram excursion. Explaining the Shuram excursion is one of the most controversial areas of geology today, with numerous proposed hypotheses. When the controversies are finally resolved, if they resolved, the Shuram and excursions, even though they go in opposite directions, I suspect will likely be both related to the dynamics of ice ages and the rise of oxygen levels. Ediacaran fauna, the first large, complex organisms to ever appear on Earth, also first appeared about 575 mya, when the Shuram excursion began. I strongly doubt that Earth’s first appearance of large complex life at the exact geological timescale moment of the wildest carbon-isotope swing in Earth’s history will prove to be a coincidence. The numerous competing hypotheses regarding the Shuram excursion include:
are created by undisturbed organism remains that become saturated with various chemicals, which gradually replace the organic material with rock by . Few life forms ever become fossils but are instead consumed by other life. Rare dynamics lead to fossil formation, usually by anoxic conditions leading to undisturbed sediments that protect the evidence and fossilize it. Scientists estimate that only about 1%-2% of all species that ever existed have left behind fossils that have been recovered. Geological processes are continually creating new land, both on the continents and under the ocean. Seafloor strata do not provide much insight into life’s ancient past, particularly fossils, because the process in “mere” . The basic process is that, in the Atlantic and Pacific sea floors in particular, oceanic volcanic ridges spew out basalt and the plates flow toward the surrounding continents. When oceanic plates reach continental plates, the heavier (basaltic) oceanic plates are subducted below the lighter (granitic) continental plates. Parts of an oceanic plate were more than 100 mya and left behind plate fragments. On the continents, however, as they have floated on the heavier rocks, tectonic and erosional processes have not obliterated all ancient rocks and fossils. The oldest “indigenous” rocks yet found on Earth are . have been dated to 3.5 bya, and fossils of individual cyanobacteria have been dated to 1.5 bya. There are recent claims of finding . The oldest eukaryote fossils found so far are of . The first amoeba-like vase-shaped fossils date from about 750 mya, and there are recent claims of finding the first animal fossils in Namibia, of sponge-like creatures which are . Fossils from might be the first animal fossils, and some scientists think that animals may have first appeared about one bya. The first animals, or , probably descended from . The is a tail-like appendage that protists primarily used to move and it could also be used to create a current to capture food. Flagella were used to draw food into the first animals, which would have been sponge-like. When the first colonies developed in which unicellular organisms began to specialize and act in concert, animals were born, and it is currently thought that the evolution of animals probably only happened . In interpreting the fossil record, there are four general levels of confidence: inevitable conclusions (such as ichthyosaurs were marine reptiles), likely interpretations (ichthyosaurs appeared to give live birth instead of laying eggs), speculations (were ichthyosaurs warm-blooded?), and guesses (what color was an ichthyosaur?).
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Dangers Of Milk And Dairy Products - The Facts
In all of these cases, theinsoluble iron from the soil or from mineralized detritus can be chemicallymodified (reduced) in the oxygen free, anaerobic areas of the substrateand become accessible to the plants through their roots.
How to Write Guide: Sections of the Paper - Bates College
Acopper test kit is needed to be sure the needed concentration levels are upand more copper may be needed after the first day because plants and otherorganics will absorb or bind with the chemical.
Food Antioxidants are Superior to Isolated Antioxidants
Allelopathy refers to the beneficial or harmful effects of one plant on another plant, both crop and weed species, from the release of biochemicals, known as allelochemicals, from plant parts by leaching, root exudation, volatilization, residue decomposition, and other processes in both natural and agricultural systems. Allelochemicals are a subset of secondary metabolites not required for metabolism (growth and development) of the allelopathic organism. Allelochemicals with negative allelopathic effects are an important part of plant defense against herbivory (i.e., animals eating plants as their primary food) (Fraenkel 1959; Stamp 2003).
16/01/2018 · Susan Roberts-Cooper
Allelopathic inhibition is complex and can involve the interaction of different classes of chemicals, such as phenolic compounds, flavonoids, terpenoids, alkaloids, steroids, carbohydrates, and amino acids, with mixtures of different compounds sometimes having a greater allelopathic effect than individual compounds alone. Furthermore, physiological and environmental stresses, pests and diseases, solar radiation, herbicides, and less than optimal nutrient, moisture, and temperature levels can also affect allelopathic weed suppression. Different plant parts, including flowers, leaves, leaf litter and leaf mulch, stems, bark, roots, soil, and soil leachates and their derived compounds, can have allelopathic activity that varies over a growing season. Allelopathic chemicals or allelochemicals can also persist in soil, affecting both neighboring plants as well as those planted in succession. Although derived from plants, allelochemicals may be more biodegradable than traditional herbicides, but allelochemicals may also have undesirable effects on non-target species, necessitating ecological studies before widespread use.
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