The correct response is "ecosystem engineer." An ecosystem engineer manipulates and engineers the habitat to benefit them in a significant way. If an ecosystem engineer like the beaver is removed from the environment, it can have detrimental effects on other species and the community structure. 

Because the organisms are genetically, behaviorally, and evolutionarily the same, they are the same species. However, their difference in location means that they cannot be in the same population. Additionally, to be in the same community, they must be in the same population. Hence, they are only related to each other by species and nothing else listed.  

The Biosphere is the collection of all biomes on Earth and the interactions between them. A species is representative of a group of organisms, while a population is a specific subset of a species. A community is the collection of all the populations that interact with each other within a given geographic area. An ecosystem is the interactions between a community and the abiotic factors within their geographic proximity. A biome is the overall interplay between similar ecosystems. Only the Biosphere contains all other answer choices within itself. 

Obviously, the smallest level of organization is the individual. This is followed by the same-species population, then the complete community of all species in a given area. Finally, the ecosystem is the largest level, including abiotic elements of the habitat.

Mutualism is when both species benefit. Commensalism is when one species benefits and the other is neither harmed nor helped. Parasitism is when one species is negatively affected by the other. 

The correct response is carrying capacity. This is threshold or limit that restricts population growth when resources are limited. Carrying capacity is the reason that we don't have billions of elephants in the world - there is only so much space and resources. The concept of carrying capacity is true for all populations in the world - including humans. 

The I=PAT equation was developed in the 1970s and it describes the impact of human population, affluence and technology on the environment. The equation is used as an aid in understanding how the size of a population, its affluence (i.e., the average consumption of each person), and the efficiency level of the population’s technology will affect the population’s general impact on the environment. The equation is simplistic and should not be seen as an accurate assessment of a population. Rather, it is a thought-provoking tool.

When graphed, the human population shows a J-shaped curve. The human population grew very slowly at first. However, its growth is exponential, so the human population doubles in a shorter time period every time. An S-shaped curve, by comparison, would show a leveling off or decrease in population.

A subspecies is the taxonomic rank below species, meaning subspecies are members of the same species, but have some characteristics that set them apart. As a result, two different subspecies of the same species are usually physically capable of interbreeding, but generally do not, due to either selection or geographic isolation.

 A niche is a habitat and way of life to which a particular organism is adapted. It is the role of a particular species within an ecosystem, including all aspects of its interaction with the living and nonliving environments.  Habituation is a common form of simple learning, defined as a decline in response to a repeated stimulus. The ability to habituate is adaptive. Humans habituate to many stimuli: city dwellers to traffic sounds, and country dwellers to the sounds of nature. A biome is a terrestrial ecosystem that occupies an extensive geographical area and is characterized by a specfic type of plant community. A community is all the interacting populations within an ecosystem. Terrioriality is the defense of an area in which important resources are located.