Bacteria are required or needed in the nitrogen cycle because other living properties cannot use atmospheric nitrogen.
<h3>What is the nitrogen cycle?</h3>
The nitrogen cycle is the sequence of operations by which nitrogen and its mixtures are interconverted in the environment.
In living organisms, It considers nitrogen fixation and pollution.
As regards Nitrogen fixation is affected, just bacteria are competent to improve atmospheric nitrogen into structures usable by other living organisms.
In nitrogen fixation, the atomic nitrogen is converted into chemical forms functional by plants and convert atmospheric nitrogen into chemical forms functional by plants.
Therefore, option A is correct.
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The Sites pebbles is the type of sediment sample that normally has the greatest permeability rate.
<h3>What is a permeability rate?</h3>
This refers to the rate at which an applied irrigation water moves through the soil.
Hence, the sites pebbles has the greatest permeability rate because it has allows a large space which helps moves unto the beneath easily.
Therefore, the sites pebbles is the type of sediment sample that normally has the greatest permeability rate.
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The Middle East has 4 different climatic regions. East coast, mountainous region, gravel planes, and the desert region.
The explanation for the differences in wavelength observed from earth and a distant star with a shift towards the red end of the spectrum is the Redshift- Doppler effect.
<h3>What is the Doppler effect?</h3>
The Doppler effect is the difference that occur between the frequency of a wave in relation to observer from the wave source.
The wavelength changes with change in the frequency.
<h3>How does the Doppler effect explain the redshift?</h3>
As an object moves away from Earth, the waves moves to the red end of the electromagnetic spectrum and becomes elongated. This results to the increase in wavelength.
Therefore, the explanation for the differences in wavelength observed from earth and a distant star with a shift towards the red end of the spectrum is the redshift-Doppler effect.
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Answer:
An analysis of 5,000-year-old genetic material from preserved human remains found in Sweden suggests that people moving from southern to northern Europe spread agriculture across that continent long ago.
In addition to agricultural know-how, the intrepid farmers brought their genes: They interbred with hunter-gatherer communities to create modern humans living in Europe today.
"Genetic variation of today's Europeans was strongly affected by immigrant Stone Age farmers, though a number of hunter-gatherer genes remain," study researcher Anders Götherström, of Uppsala University in Sweden, said in a statement.
The results of this study, to be published in the April 27 issue of the journal Science, match up well with previous archeological evidence of farming in Europe.
Explanation:
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