A stable population is described as one in which birth rate equals to death rate, and the number of children is about equal to the number of reproducing adults.

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.

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.

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.

A species is "endemic" when it is found only in one particular location. The flightless cormorant, marine iguana, and Galapagos penguin are all examples of species that are endemic to the Galapagos Islands.

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.

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.

Least concerned refers to the lowest risk where species members are abundant. Near threatened means the species is likely to become endangered at some point. Vulnerable means that, in the wild, the species are at high risk for becoming endangered. Endangered is similar to vulnerable, but has a high risk of extinction, not just endangerment. Extinct means there are no more members of the individuals in a species remaining. The correct ranking is as follows: least concerned, near threatened, vulnerable, endangered, and extinct.

The correct answer is “metapopulation model.” It describes multiple sub-populations that are connected together in a larger, metapopulation. This is typically shown as patches within a larger landscape. The patches represent sub-populations. Individuals can migrate from one patch to another, but they are all part of the same population.

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.