In fruit flies, white eyes (r) are recessive to red eyes (R) on the X-chromosome. A heterozygous red-eyed female fruit fly is crossed with a red-eyed male fruit fly and
What are the possible phenotypes with ratios for the offspring fruit flies?
What are the possible genotypes with ratios for the offspring fruit flies?

the offspring would all be white. if the parents are both white flowers then they have the genotype rr, which when crossed results in an all white punnet square.

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).

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.