When more than one gene controls a trait it is called "<span>define polygenic inheritance".
I hope this helped!</span>
<span>The answers are visual spectrum and pupil. The visible light spectrum is a narrow band of frequencies ranging from 390 to 780 wavelengths long. These wavelengths are detectable by the eye and the different length corresponds to different colors.
The pupil determines how much light can enter the eye. It dilates and constricts depending on the amount of light available.</span>
Answer:
Salmon populations in the United States is declining due to the following factors:
1. Over-fishing and human activities have put a major influence on the population of salmon.
2. Due to industrialization, urban growth, unplanned farming, deforestation, and pollution would have imparted strains on the stocks of salmon. Apart from this chemical contamination from the industrial run-off and agricultural activities are also declining populations of salmon.
3. Genetically modified fish from hatcheries usually escape and interbreed with wild fish, thus, changing the genetic features of the populations.
4. Construction of hydropower dams is also a major cause of the salmon population declining.
