Answer:
protected; increase
Explanation:
Ozone is composed of trioxygen which is highly reactive gas compared to dioxygen. Ozone layer is present in stratosphere and troposphere and protect the humans from ultraviolet radiations but it may be toxic if inhaled. Ozone can be broken down into molecular oxygen by chlorine and bromine atoms.
A hole was discovered in ozone layer in 1982 and scientist believed that it could be dangerous for human health. The compounds involved in depletion of ozone are mainly Chlorofluorocarbons (CFS) and (HFCS). Then a global agreement was signed in 1987 which leads to prohibition of use of all chemicals that are involved in depletion of ozone layer. The problem of ozone depletion is solved by the agreement and ozone hole started to recover it from 2000.
But recent reports showed that the alternative chemicals used to protect the depletion of ozone layer began to trap the heat inside the earth like greenhouse effect. Now scientists are in search of chemical that can prevent both ozone depletion as well as global warming.
A) <u>Mutation</u> is the original source of variations for plants and other organisms which develops differences among their respective species
Explanation:
Genetic variation leads to the natural differences between each individual and among individuals of a species. The main cause for this variation is due to alleles that cause variations in the composition of genes or the DNA sequences.
A mutation is a genetic variation which leads to the creation of a new allele in a species population. Each variation in the DNA sequence leads to an allele formation and each allele leads to a difference in character or trait between individuals since they are the alternate version of the original genes.
Although genetic variations could be brought about by crossing over, random fertilization, or independent assortment; mutation is the original source because it provides the basic raw material for all the evolutionary changes.
This is known as double helix. Nucleotides each have three parts: phosphate, sugar molecule<span>, and one of four </span>bases<span>. The </span>bases<span> include: A, (adenine), g (guanine), t (thymine), c (cytosine). ... </span>Explain why complementary base pairing is necessary to maintain the double helix shape of the DNA molecule<span>.</span>