Saliva's buffering capacity and flow of secretion are directly related to the rate and extent of demineralization. ... Saliva can act as a replenishing source and inhibit tooth demineralization during periods of low pH, while promoting tooth remineralization when the pH returns to a neutral state.
Explanation:
Mutations on DNA create genetic variation and diversity on which natural selection acts upon. Mutation can be advantageous, disadvantageous or neutral. Those mutations that confer advantage are preserved in the population while those that are DISadvantageous are weeded out. This occurs because advantageous traits that give a particular advantage to individuals in the environment, however slightest, give them an increased chance of survival and passing their genes to subsequent generations.
An example is mutation that causes sickle cell-shaped blood cells. Individuals with sickle cell blood are less likely to contract malaria. Therefore in an environment where malaria is endemic, the population will have a higher allele frequency for sickle cell alleles that populations in non-endemic areas.
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Answer:
Iceland sits spanning the Mid-Atlantic Ridge tectonic plate boundary which separates the Eurasian and the North American plates.
Explanation:
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Answer:
Helium nuclei is emitted during alpha decay.
Explanation:
Alpha radiations are emitted as a result of radioactive decay. The atom emit the alpha particles consist of two proton and two neutrons. Which is also called helium nuclei. When atom undergoes the alpha emission the original atom convert into the atom having mass number 4 less than and atomic number 2 less than the starting atom.
Properties of alpha radiation:
Alpha radiations can travel in a short distance.
These radiations can not penetrate into the skin or clothes.
These radiations can be harmful for the human if these are inhaled.
These radiations can be stopped by a piece of paper.
Example:
₉₂U²³⁸ → ₉₀Th²³⁴ + ₂He⁴ + energy
Explanation:
A) fission: Iodine-140 (atomic number = 53)
B) fusion: 1 neutron
C) fission: Uranium-233 (atomic number = 92)
