Answer:
The correct answer is D. Desertification can happen as a result of non-sustainable agriculture.
Explanation:
Desertification is a process of ecological degradation in which the fertile and productive soil loses all or part of the production potential. This happens as a result of deforestation and destruction of the vegetation cover, the subsequent erosion of the soils, the overexploitation of aquifers, the over-irrigation and consequent salinization of the lands or the lack of water; human beings frequently favor and increase this process as a result of activities such as excessive cultivation and grazing or deforestation. According to data from the United Nations Environment Program (UNEP), 35% of the surface area of continents can be considered as desert areas, within these territories millions of people survive in conditions of persistent drought and food shortages. Among many other factors, it is considered that the expansion of these deserts is due to human actions.
Answer:
B)
Explanation:
In order for one thing to happen another must come first and in this case, in order for secondary succession to happen the land must first go through primary succession and then be killed off by a volcano or other things.
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Answer:
The 5' end has free phosphate group while the 3' end has free OH group.
Explanation:
Each DNA strand has two ends that differ from each other with respect to the functional group. The nucleotide present at the 5' end of a DNA strand has a free phosphate group. This phosphate group of other nucleotides of the DNA strand is bonded in phosphodiester bonds. Likewise, the 3' end of a DNA has a free OH group. This makes the two ends of a DNA strand quite different from each other. A DNA new nucleotide can be added to the 3' end due to the presence of a free OH group.