Populations and Communities - AP Environmental Science

By definition a population is all persons, plants, or animals inhabiting a specified area. A community is the interacting populations within an ecosystem. A gene pool is the total of all alleles of all genes in a population. The definition of an inhabitant is a person or animal that lives in or occupies a place. An organism is any living thing, plant, or animal.

Populations consist of individuals of the same species in a common area. Communities are made up of groups of populations of different species within a given geographic range. Last, a niche refers to the specialized role and position that a species has within its environment.

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.

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.

Population growth is an underlying cause of depletion and premature extinction of a wild species, but is not a direct cause. On the other hand, habitat loss is a direct cause of depletion and premature extinction of wild species due to processes like over logging, damming rivers, or urban development. Pollution is a direct cause of extinction in the wild, usually caused as streams, rivers, and oceans are polluted. The introduction of an invasive, nonnative species to an environment can create an unbalanced ecosystem, directly causing extinction of wild species. These invasive species are often harmful and fill niches previously occupied by native species. Increasing predator species in an area can significantly reduce or drive prey species to extinction. Similarly, increasing the use of pesticides and pest controls can directly cause extinction of organisms in the affected ecosystem.

A population is a collecting of individuals from the same species. Populations are a unit of organization that has measurable properties, such as population density and home range. Populations are altered by birth and death, immigration, and emigration.

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 answer is “evenness.” All the other terms describe life history traits. “Maturity” refers to the age of first reproduction. “Parity” is described as the count of reproduction events. Last, “fecundity” is defined the number of offspring at each reproduction event.

The correct response is “keystone species.” A keystone species makes up a small portion of community; however, it has a major impact on the community structure despite making up a small percentage of the ecosystem that it inhabits. "Dominant species" have large number and large impacts; thus, this answer choice does not fulfill the disproportionate part of the description. "Common species" and "rare species" both have low impacts on the community structure, so they are poor answer choices.

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.

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.

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.

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.

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.

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.