Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.
Mortality, or death rate is a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of the time. In this case a factor that would result to an increased mortality rate in a population due to increased competition of water will be the density-dependent factor.
Enable members of a phylum to survive and reproduce
Light , water , temperature & nutrients
The reference point = a object used for comparison to determine if something is in motion.
An object is in motion if it changes position relative to a reference point.
You assume that the reference point is stationary, or not moving.