The ribosomal RNA studies that led to the division of prokaryotic organisms into the bacteria and the archaea were begun by Woese.
Ribosomal RNA makes the maximum portion of RNA in the cells. However, it is not translated into proteins. But it plays a major role in the translation of m-RNA. They are responsible for deducing the order of the amino acid sequence and linking the amino acids together to form the polypeptide.
Archaea are a group of organisms that are similar to bacteria, yet have evolutionary differences. They are found in extreme locations like hot spring, salty water bodies, or areas where methane if formed. Therefore, they are also known as extremophiles.
To know more about archaea, here
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Answer:
The correct answer is: geography and UV radiation.
Explanation:
Skin variation occurred thanks to evolution, and was driven as a consequence of the geographical location of different populations of humans.
The humans that lived in hot and sunny places, closer to the equator, where much more exposed to the sun's ultraviolet radiation. In order to survive the amount of UV lights that they were exposed to, new humans in those regions were being born with a darker skin tone, which was rich in melanin (a brown pigment that protects us from the sun radiation).
Contrary to these humans that lived in the tropical areas, the humans that populated the areas that were closer to the poles, developed much lighter skin as a result of lower amounts of melanin in their skin. Since sun exposure in the poles is very limited, humans needed to receive as much as they could for the production of Vitamin D, and thus, their skins got lighter and less protected.
Dispositional traits are personality traits that remain stable and relatively unchanging from about age. They refer to the tendency of an individual to behave in stable and predicted ways. It is similar with the concept of moods. Costa and McCrae believed that personality traits remain the same by the age of 30.
This is an example of negative feedback.
After a big meal, glucose levels in the bloodstream increases. The body recognises this change and goes through homeostasis, or the regulation of bodily state or internal environment.
The pancreas secretes insulin, which then binds to insulin receptors. This will result in the uptake of excess glucose from the bloodstream into cells and converted into glycogen to be stored in cells as energy storage molecules.
Since there is the counter effect of body (i.e. when blood-glucose concentration increases, the body sends a signal to decrease the blood-glucose concentration, this is called a negative feedback (instead of a positive feedback, which occurs if for e.g. the body signals cells to increase blood-glucose concentration even after blood-glucose concentration increased after a heavy meal).
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