An ecological niche is the sum of a species’ use of its environment, including both biotic and abiotic factors. Resource partitioning is the differentiation of niches; it is impossible for two species to have the same niche and use the same resources. Resource partitioning allows for differentiation of niches between similar species so they can coexist. A fundamental niche is described in forest B, where moss 2 grows both above and below the shrubbery. It is the niche that could be potentially occupied by a species. The realized niche is the term that refers to the area of moss 2 in forest A. The realized niche is the portion of the fundamental niche that an organism actually occupies. We know that moss 2 can potentially occupy areas above and below shrubbery, but in forest A, it only occupies the area below the shrubbery (its realized niche). 

The term “abiotic” refers to the nonliving components of the environment; therefore, a rock would be characterized as an abiotic part of the environment.

Human activities can have negative impacts on the proper functioning of ecosystems and environments. One human activity that has a direct impact on marine environments is overfishing, which may critically change the delicate balance of the ecosystem.

A community includes populations of different species. The study of a community looks at interactions between species, such as competition, symbiotic relationships, or predation. 

Disease is a biotic factor, while the other choices are abiotic factors. Density-dependent factors are biotic in nature, and may involve things such as mating, food, competition, and disease. Density dependent factors will affect different populations differently depending on how many organisms are present in a given area. In the case of disease, consider that the flu will spread more easily in a densely-populated city than it will in a loosely-populated desert.

The other answer options will affect a population the same, regardless of density, because they affect large areas with the same magnitude.

Negative feedback inhibition prevents populations from continually increasing in size. Without these such factors, population sizes would not be controlled. For example, perch feed on and find shelter in kelp. Where there are too many perch, there is not enough kelp to sustain them all (for food and shelter), and the fish population decreases in size. When there are less perch, there is enough kelp for them to feed on and hide in. Because conditions are favorable, the perch numbers increase. This negative feedback inhibition is density dependent and controls population size dynamics. 

K-selection is density dependent selection, while r-selection is density independent selection; the two are opposites. While all the answer choices are related, only one displays the same (opposite) relationship: semelparous and iteroparous.  Semelparous refers to the “one shot” reproductive trend, producing many offspring only once during an organism's lifetime. Iteroparous refers to organisms that breed multiple times, producing few offspring each time. For semelparous organisms, survival is low and the environment is generally unpredictable. For iteroparous organisms, survival rates are high and the environment is stable and dependable.  

The logistic growth model shows that population size levels off as it approaches its carrying capacity. In this situation, as the population increases and resources are used, the population approaches its carrying capacity, which is the maximum population size that the environment can support. The exponential growth model is unrealistic, as it shows a population’s growth when resources are abundant, but this there is no environment where resources are always in abundance. Survivorship curves show the life patterns of species; rather than comparing the relationship between resources and population size, these types of graphs compare age and population size.  

A clumped pattern of dispersion occurs when individuals aggregate in patches. For example, a herd of cows all graze in a field together, as it is their only source of food within five miles. Uniform dispersion is when organisms are evenly spaced throughout a given area. This results from territoriality, or when organisms defend their physical space against other organisms. Random dispersion is the unpredictable spacing of organisms throughout a given area. There are no strong attractions or repulsions among individuals that would result in clumped or uniform dispersion; the animals are scattered randomly.  

Life tables are summaries of the survival patterns of a population. They are constructed using cohorts (groups of individuals of similar age). By following and observing these individuals from birth until death, researchers can make life tables and plot survivorship cures, showing the number of cohorts alive over their lifetimes.