The electrons are used to generate ATP and its equivalent forms.
I believe the answer you are looking for is they are all body systems found in the human body, or organ systems.
If a dihybrid F1 plant, self-fertilizes, the F2 progeny will have two types of phenotypes. One would be the dominant trait phenotype for both the alleles, which would be possessed by 3/4th of the population.
Other would be recessive trait phenotype for both the alleles, which would be possessed by 1/4th of the population.
One fourth of the population would be true-breeding for the dominant traits.
Half of the population would be heterozygous for both traits and would have dominant phenotype
Rest one-fourth population would be homozygous for both recessive traits
