The decay of uranium isotopes is used to provide information about the age of Earth.
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Explanation:</h3>
Isotopes of Uranium U-232, U-233 , U-234 , U-235 , U-236 , U-238 are used as fuel in nuclear reactors or as explosives for nuclear weapons. Uranium 238 is not very radioactive and it constitutes for nearly 99.3% of natural uranium on Earth and has the longest lifetime: its period is 4.5 billion years, about the age of Earth.
Use of radiometric dating techniques help in defining the age of substances (natural or man-made) using the known decay rates of radioactive elements. Each element has an individual decay rate and half life time.
Two Uranium isotopes (U-238 and U-235) are used for radiometric dating. Both the isotopes have different decay rates and half life period. Both are unstable and radioactive. Since two different isotopes produce two different decay clocks (one as a reference to other), it is beneficial in accurately determining the age of samples. The age of earth (rocks or other natural elements) can be easily determined using Uranium isotopes.
Answer:
The correct answer is "the S layer may play a role in protecting cells from viruses and predatory bacteria found in nature but not in laboratory cultures".
Explanation:
The S-layer (surface layer) is a part of the cell's envelope comprised of of identical proteins or glycoproteins that could be found in archaes and some bacterias in nature. The function of the S-layer is unknown, however the fact that is only seen in nature suggest that it may play a role in protecting cells from viruses and predatory bacteria found in nature but not in laboratory cultures. It is likely that archaes and bacteria synthesize the S-layer when they recognize viruses and predatory bacteria in nature, the S-layer is not synthesized in laboratory cultures because these pathogens are not present.
Explanation:
To calculate the pH of an aqueous solution you need to know the concentration of the hydronium ion in moles per liter (molarity). The pH is then calculated using the expression: pH = - log [H3O+].
Explanation:
Generation time is the time taken for a cell population to double in numbers and thus equivalent to the average length of the cell cycle.
(Assuming that this is about chromosomes)
A male has an XY combination in his chromosomes.
