Why are most factors held constant in a scientific experiment?

Larry goes to the doctor complaining that he can't see the right side of the visual field with either eye. where in the visual signal-processing pathway is larry's problem occurring?

Gene expression is the activation of a gent that results in a question 1 options: protein dna mitochondria

In a population that is in hardy-weinberg equilibrium, there are two possible alleles for a certain gene, a and a. if the frequency of allele a is 0.4, what fraction of the population is heterozygous? a. 0.40 b. 0.60 c. 0.16 d. 0.48