In the case of the gene that determines high cholesterol in the blood, the two alleles express incomplete dominance.
What this means is that the dominant allele is not completely dominant over the recessive allele. If the allele was completely dominant, even one allele would be enough to determine the individual's trait as dominant. But in the case of incomplete dominance between the alleles, the heterozygous individuals that have one dominant and one recessive allele are an ''in between'' phenotype.
When blood is in the lungs,
where oxygen is plentiful, oxygen easily binds to the first subunit and then quickly fills up the remaining ones. Then, as blood circulates through the body, the oxygen level drops while that of carbon dioxide increases. In this environment, hemoglobin releases its bound oxygen.
The right option is the second option, which states "<span>fur color that closely matches the eucalyptus bark color</span>". Change is in the fur color of Koala's to match the bark color of eucalyptus tree is a structural adaptation that fits them for their habitat as tree-dwellers.
An organism that can live in only one particular environment or that can survive on only one type of food would be called a specialist.