Human skin color is a polygenic trait, which means that multiple gene loci (with different alleles) are involved in its expression. It has been shown that there more than 350 genetic loci involved in determining skin color. Because of that, there is the enormous number of possible genotypes for the skin color and as a result, the phenotypes vary from the darkest brown to the lightest hues. Different populations have different allele frequencies of genes for human skin color, and the combination of these allele variations brings about complex and continuous variation in skin coloration. Natural skin color can change due to exposure to sunlight (becomes darker) and that is the way it adapts to intense sunlight irradiation (protection against the UV exposure).
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This type of classification used to be used when classifying the protostome organisms.
In this type of organism, the oral cavity develops from the blastophore, the initial cavity in the gastrula, an early stage of the development of the embryo.
Answer:
b) and c)
Explanation:
Greenhouse gases are gases found in the atmosphere that absorb infrared radiation and trap the sun’s heat, thereby producing an effect known as <em>greenhouse effect.</em> By this natural way, the earth is able to be kept warm at an optimal temperature, to make it habitable for humans and other organisms. These gases referred to as <em>greenhouse gases</em> include, carbon dioxide, methane, water vapour and other trace gases found in the atmosphere. Greenhouse gases could be likened to the glass in a greenhouse that helps in trapping heat to keep the greenhouse warm at optimal temperature necessary for plant growth and development.
Without this natural greenhouse effect caused by greenhouse gases, life on earth would be almost impossible as the earth would almost be covered with ice below 0 degrees Fahrenheit.
The increased level of greenhouse gases we now find in the earth’s atmosphere is responsible for the additional warming of the earth’s surface, causing an enhanced greenhouse effect which results in global warming.
Statement a) cannot be used as an explanation because it is false. Greenhouse effect makes the earth habitable.
Statement d) cannot be used as an explanation because carbon dioxide is not the only greenhouse gas that matters. Water vapour, CFC and methane also have impacts.
<em>Statement b) and c) are the best statements to use in explaining the true nature of greenhouse effect.
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