Answer:
The correct answer is "#2 and #3 only"
Explanation:
A and a are alleles, and R and r are alleles. Alleles of a gene are found at the same locus on homologous chromosomes. Every pair of the alleles depicts the genotype of a particular gene. Homozygous genotype occurs when two similar alleles at same locus and heterozygous in case of two nonidentical alleles. Due to the alleles there occurs a change in the appearance. An alleles create differences in gene.
Animals gives us nutrients because of the food they eat
They breathe through their skin. Air dissolves on the mucus of their skin, so they MUST stay moist to breathe.
If worms dry out, they suffocate. As fresh air is taken in through the skin, oxygen is drawn into the worm's circulatory system, and the worm's hearts pump the oxygenated blood to the head area.