<span>A polygenic trait is contributed by two or more genes one gene two alleles multiple alleles. True!</span>
Answer:
Phosphorus is essential for growth of plants and other organisms. When concentration of phosphorus mostly from high breeding rate e.g., pigs, cattle etc. rise in water it causes severe growth of plants and algae as well as phytoplanktons. As a results layers of phosphorus start to release phosphorus as well due to positive gradient. These reactions in water are iron-redox reactions that are crucial for the release of phosphorus.
When too much phosphorus accumulates, it produces a degrading growth feedback in plants, algae and phytoplanktons that then shift toward excessive nitrogen available from fertilizers and cause a flip from P to N. Cynobacteria now dominates and denitrification as well as nitrification takes place simultaneously.
Severe eutrophication induces hypoxia in water that cause a major damage to plants biodiversity in the environment.
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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It would be the endocrine system.
The route sperm take through the human male reproduction by C. Vas deference, epididymis then the Urethra.