Most likely to involve the amygdala.
This is called incomplete dominance. When an something is heterozygous for an incomplete dominant gene, the resulting phenotype will be somewhere between the two. For example if a plant has a tall allele and a short one, but neither shows complete dominance over the other, the plant height will be somewhere in the middle.
I'm pretty sure these include light availability, oxygen levels, water movement, salinity, density and pH. These conditions often vary from habitat to habitat and will either support or limit the life processes of the marine organisms living there.
Hopefully that's right.
I would say this is an expository text.