I would go with the first option
Answer:
I, II, III
Explanation:
A threshold stimulus is a stimulus that is capable to produce a response in excitable tissues such as neurons and muscle fibers. At threshold potential, the outward movement of K+ and inward movement of Na+ become equal to each other. When the potential exceeds the threshold potential, more and more Na+ enter the cell to depolarize it and to allow the opening of Na+ channels. Therefore, to fire an action potential, the threshold must be exceeded.
Conduction of action potential is all or none phenomenon which means that either it occurs or it does not occur. As an impulse is passed by each successive part of an exon, it enters the refractory period during which there is no conduction of nerve impulse. It ensures the one-way conduction of impulse from the cell body to the axon terminal only.
Answer:
Testing positive for HIV means a high chance of death and a good chance of lower reproduction rates. But some people are immune to HIV, which makes them more evolutionarily fit, likely to live longer, likely to reproduce more, which would increase the frequency of the immune allele in the population. Over time, this increase in frequency of the gene that causes immunity could spread across the human race and cause it to evolve.
Answer:
Dominant
Explanation:
The dominant allele will always be shown in the phenotype if it's present, because the other allele would be dominant or recessive. If both alleles are dominant, then the dominant one shows, if one of the alleles is recessive, then the dominant allele would show over the recessive one.
I think of recessive alleles as "weak" where, they just follow behind whichever other allele exists there. If the other one is dominant, then the recessive one is behind it, and no one can see it. If it other allele is recessive, a recessive allele will be in front.
Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring
