Answer:
Ozone layer... pollution
Explanation:
The ozone layer is a layer in the atmosphere which provides a barrier between harmful UV rays and the Earth. However, pollution is quickly depleting the layer which in turn creates a higher risk of skin cancers and other conditions caused by harmful UV rays.
There was no life on Earth for the first billion years because the atmosphere was not suitable for life. Earth's first atmosphere had lots of water vapor but had almost no oxygen. Later, frequent volcanic eruptions put several different gases into the air.
The system of classification relates to the diversity of species because the system of classification is how we organize the diversity of species. With out it we would have a hard time trying to determine which animals belong with which group. There would be no order, just chaos of trying to determine animal likeness of one another.
To cut this answer short, it helps them organize organisms.
The right answer is B and C.
For proposal C, I will give you an example, that of an autosomal recessive disease. If a parent is heterozygous for an allele causing an autosomal recessive disease (due to a mutation), it may be that it transmits the allele to its descendence, as it may not be able to transmit it (since in one heterozygous subject, not all of its gametes carry the mutated allele) and thus the mutation will no longer be copied through the generaitons.
Each individual is genetically unique. Its genes are distributed along chromosomes contained in the nucleus. Mutations can lead to the appearance of different versions of genes: alleles. A diploid individual has two copies of each gene, which may be identical or different alleles. Mixing during sexual reproduction partly explains the genetic diversity of individuals.
Explanation:
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