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What drove circadian rhythms to evolve has been an enigmatic question. Previous hypotheses emphasized that photosensitive proteins and circadian rhythms may have originated together in the earliest cells, with the purpose of protecting replicating DNA from high levels of damaging ultraviolet radiation during the daytime. As a result, replication was relegated to the dark. However, evidence for this is lacking, since the simplest organisms with a circadian rhythm, the cyanobacteria, do the opposite of this - they divide more in the daytime. Recent studies instead highlight the importance of co-evolution of redox proteins with circadian oscillators in all three kingdoms of life following the Great Oxidation Event approximately 2.3 billion years ago. The current view is that circadian changes in environmental oxygen levels and the production of reactive oxygen species (ROS) in the presence of daylight are likely to have driven a need to evolve circadian rhythms to preempt, and therefore counteract, damaging redox reactions on a daily basis.
What is theorized to have evolved with circadian rhythms?
A: photosensitive proteins

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The state is among the best in pre-kindergarten education, and the National Institute for Early Education Research rated it first in the United States with regard to standards, quality, and access to pre-kindergarten education in 2004, calling it a model for early childhood schooling. High school dropout rate decreased from 3.1 to 2.5 percent between 2007 and 2008 with Oklahoma ranked among 18 other states with 3 percent or less dropout rate. In 2004, the state ranked 36th in the nation for the relative number of adults with high school diplomas, though at 85.2 percent, it had the highest rate among southern states.
Who said Oklahoma's pre-K program is the best in the US?
A: National Institute for Early Education Research

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A number of events in 2006 pushed renewable energy up the political agenda, including the US mid-term elections in November, which confirmed clean energy as a mainstream issue. Also in 2006, the Stern Review made a strong economic case for investing in low carbon technologies now, and argued that economic growth need not be incompatible with cutting energy consumption. According to a trend analysis from the United Nations Environment Programme, climate change concerns coupled with recent high oil prices and increasing government support are driving increasing rates of investment in the renewable energy and energy efficiency industries.
In what year did a number of events push renewable energy up the political agenda?
A: 2006

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Because of Oklahoma's position between zones of differing prevailing temperature and winds, weather patterns within the state can vary widely over relatively short distances and can change drastically in a short time. As an example, on November 11, 1911, the temperature at Oklahoma City reached 83 °F (28 °C) in the afternoon (the record high for that date), then an Arctic cold front of unprecedented intensity slammed across the state, causing the temperature to crash 66 degrees, down to 17 °F (−8 °C) at midnight (the record low for that date); thus, both the record high and record low for November 11 were set on the same date. This type of phenomenon is also responsible for many of the tornadoes in the area, such as the 1912 Oklahoma tornado outbreak, when a warm front traveled along a stalled cold front, resulting in an average of about one tornado per hour over the course of a day.
How fast did the 1912 tornado outbreak make tornadoes?
A:
one tornado per hour