Populations, Communities, and Ecosystem Dynamics

Comprehensive vocabulary flashcards covering population ecology, limiting factors, human demography, ecological niches, community succession, and biodiversity conservation.

Geographic Range

The area inhabited by a population, which can vary enormously from a few cubic meters for small organisms up to many square kilometers for larger organisms.

Population Density

The number of individuals of a single species per unit area.

Population Distribution

The way individuals are spaced out across their geographic range, typically described as random, uniform, or clumped.

Age Structure

A description of a population that includes the ages of individuals and the number of males and females, helping to predict reproductive habits and future shifts.

Immigration

The movement of individuals into a new area or region.

Emigration

The movement of individuals out of an area or region, often occurring when environmental conditions change or resources become scarce.

Exponential Growth

A growth pattern in which a population increases more rapidly as more offspring are produced, occurring under ideal conditions with unlimited resources.

Invasive Species

An introduced organism whose population can grow exponentially due to a lack of natural predators, often outcompeting native wildlife and triggering population declines.

Logistic Growth

A growth pattern that occurs when a population's growth slows and then stops following a period of exponential growth.

Carrying Capacity

The maximum number of individuals of a particular species that a given environment can support, dictated by abiotic and biotic factors.

Limiting Factor

Any biotic or abiotic factor that controls the growth of a population and determines the carrying capacity of an environment.

Density-Dependent Limiting Factors

Limiting factors that operate strongly only when population density is high, including competition, parasitism, disease, stress from overcrowding, predation, and herbivory.

Density-Independent Limiting Factors

Limiting factors that affect all populations regardless of size or density, such as extreme weather events (hurricanes, droughts, floods) and natural disasters like wildfires.

Demography

The scientific study of human populations, which examines birth rates, death rates, and age structure to explain how populations change over time.

Thomas Malthus

An English economist and demographer who argued that human population growth is limited by scarce resources, postulating that only war, famine, and disease keep populations in check.

Demographic Transition

A dramatic shift in a population over time from high birth and death rates to low birth and death rates, historically driven by industrialization, healthcare, and education.

Age Structure Diagram

A graphical representation showing the distribution of a population based on age and sex, where a pyramid shape predicts future growth, a rectangle indicates stability, and an inverted pyramid signals decline.

Habitat

An area characterized by a particular combination of physical and biological environmental factors where an organism lives; considered an organism's ecological address.

Microhabitat

A very small, specialized part of a larger habitat where small organisms live under unique localized conditions.

Tolerance

The range of external environmental conditions within which a species can survive, reproduce, obtain energy, and maintain homeostasis.

Ecological Niche

The full range of physical and biological conditions in which an organism lives and the way it interacts with biotic and abiotic factors to obtain necessary resources.

Competitive Exclusion Principle

The ecological rule stating that no two species can occupy exactly the same niche in exactly the same habitat at exactly the same time without one outcompeting and excluding the other.

Keystone Species

A species that plays a vital and unique role in maintaining the structure, stability, and biodiversity of an entire ecosystem, whose removal causes disproportionate disruption.

Symbiosis

A particularly close, interdependent relationship between two distinct species that live together.

Commensalism

A symbiotic relationship in which one organism benefits while the other is neither helped nor harmed.

Mutualism

A symbiotic relationship in which both interacting species receive a benefit.

Parasitism

A symbiotic relationship where an organism lives on or inside a host organism, deriving nutrition from it while causing it harm.

Ecological Succession

A series of somewhat predictable changes that occur in an ecological community over time, especially following a disturbance.

Primary Succession

Ecological succession that begins on newly formed rock, volcanic flows, or areas with no remnants of an older community.

Pioneer Species

The first hardy species to colonize barren areas, possessing broad tolerance ranges suitable for surviving on bare rock (e.g., lichens).

Secondary Succession

Ecological succession that occurs in areas affected by a disturbance but not entirely destroyed, proceeding more quickly because soil and seed remnants are already present.

Climax Community

A specific, mature community resulting from ecological succession, which can reproduce the original ecosystem after natural disturbances but may vary or remain patchy.

Biodiversity

The total of all genetically-based variation in all organisms in an environment, encompassing ecosystem diversity, species diversity, and genetic diversity.

Ecosystem Diversity

The variety of habitats, living communities, and ecological processes in a biome or across the biosphere.

Species Diversity

The number of different species found in a biome, ecosystem, or habitat.

Genetic Diversity

The total variety of all different forms of genes and genetic information present within a particular species or population.

Ecosystem Resilience

The capacity of a natural or human system to adapt, recover, and regain functional equilibrium following an environmental disturbance.

Ecosystem Services

Vital natural benefits and processes provided by healthy, functioning ecosystems, such as water purification, crop pollination, and carbon storage.

Conservation Biology

The branch of biology dedicated to preserving and protecting natural resources, individual species, ecosystems, and ecosystem services.

Biodiversity Hotspot

A biogeographic region that is home to a significant number of endemic species found nowhere else and is in immediate danger of habitat destruction.