Ecology: Succession, Population Dynamics, Interactions, and Biogeochemical Cycles

Comprehensive vocabulary flashcards covering ecological succession, habitat and niche definitions, species interactions, population growth models, life-history strategies, and biogeochemical cycles.

Ecological Succession

The gradual, sequential replacement of plant communities in an area over time, representing a process of change in the species that make up a community.

Primary Succession

A type of ecological succession that begins in an area where life has never existed before, such as on fresh lava flow or exposed bare rock.

Pioneer Species

The first organisms to colonize a barren habitat that modify the environment to make it suitable for other species, such as lichens and mosses breaking down bare rock to initiate soil formation.

Seral Communities

Intermediate ecological communities that sequentially replace pioneer communities, characterized by stages such as grasses replacing lichens and mosses, or shrubs replacing grasses.

Climax Community

The final, most stable stage of ecological succession that persists over time as long as the area remains undisturbed, such as a tropical rainforest or temperate forest.

Secondary Succession

A type of ecological succession that occurs when a disturbance disrupts an existing ecosystem (such as fire, timber harvesting, wind, or grazing) but leaves the underlying soil intact.

Habitat

An area characterized by a distinct combination of physical and biological environmental factors that determine which organisms can survive within it.

Microhabitat

A localized, tiny part of a much larger habitat that possesses its own distinct set of environmental conditions known as a microclimate.

Microbiome

A microscopic microbial community occupying a specific environment or microhabitat.

Tolerance

The range of external environmental conditions within which a species is capable of surviving and reproducing.

Niche

The full range of physical and biological conditions in which an organism can survive and reproduce, together with the way it obtains and uses the resources it needs.

Intraspecific Competition

Competition that occurs between individuals of the same species as they attempt to use the same limited ecological resources at the same time and place.

Interspecific Competition

Competition that occurs between members of different species attempting to utilize the same limited ecological resources in the same habitat at the same time.

Competitive Exclusion Principle

The ecological principle stating that no two distinct species can occupy exactly the same niche in exactly the same habitat at exactly the same time.

Predation

An ecological interaction where one organism hunts and feeds on another organism, driving coevolution and coupled cyclic population dynamics between predator and prey.

Keystone Species

A species that plays a critical and unique role in sustaining the overall structure, stability, and biodiversity of an entire ecosystem.

Symbiosis

A close biological relationship in which individuals from two different species live together in direct and prolonged contact.

Commensalism

A symbiotic relationship in which one organism benefits while the other is neither helped nor harmed, such as Spanish moss growing on a tree or Demodex mites residing in human eyelash follicles.

Mutualism

A symbiotic relationship in which both participating organisms derive mutual benefits, such as clownfish living with sea anemones or digestive tract bacteria in cattle helping to digest grass.

Parasitism

A symbiotic relationship in which one organism (the parasite) benefits by living inside or on another organism (the host) while harming it.

Limiting Factor

Any ecological or environmental factor that restricts the growth or holds down the overall size of a population.

Density-Dependent Limiting Factors

Limiting factors whose impact increases or decreases depending on the population density of an area, such as predation, competition, parasitism, and disease.

Density-Independent Limiting Factors

Limiting factors that affect a population's size and growth regardless of its density, such as unusual weather, natural disasters, and human activities.

Population Density

The number of individual organisms of a species living within a specifically defined spatial area.

Population Dispersion

The spatial arrangement and pattern of spacing of individual organisms across a given geographic area, categorized as clumped, uniform, or random.

Survivorship Curve

A generalized graph that illustrates the number or proportion of surviving individuals from an initial measured cohort across successive age intervals over time.

Type I Survivorship

A survivorship curve characterized by low infant mortality and high survival rates through middle age, with mortality concentrated among older age groups, common to large mammals and humans.

Type II Survivorship

A survivorship curve characterized by a relatively constant mortality rate across all life stages, typical of birds and reptiles.

Type III Survivorship

A survivorship curve characterized by very high birth rates combined with extremely high infant and juvenile mortality, typical of invertebrates and plants.

Exponential Growth

A rapid and continuous population increase that occurs under conditions of abundant resources, producing a J-shaped curve composed of an initial lag phase and an exponential growth phase.

Logistic Growth

A population growth pattern that slows and stabilizes after an exponential phase due to resource constraints, producing a characteristic S-shaped curve.

Carrying Capacity

The maximum number of individuals of a population that a specific environment can sustainably support over time.

$r$-Strategists

Species characterized by a short lifespan, small body size, rapid reproduction, production of numerous offspring, and minimal to no parental investment, such as bacteria, weeds, and cockroaches.

$K$-Strategists

Species adapted to stable environments near carrying capacity, characterized by long lifespans, large body sizes, slow reproduction, few offspring, and high levels of parental care, such as humans and elephants.

Biogeochemical Cycle

The movement and recycling of a specific chemical element or molecule through the biological (biosphere) and physical (geosphere, hydrosphere, atmosphere) components of ecosystems.

Hydrologic Cycle

The circular pathway of water across Earth involving evaporation, transpiration, condensation, precipitation, surface runoff, and groundwater seepage.

Transpiration

The physiological process by which moisture is released from plant leaves into the atmosphere as water vapor in the hydrologic cycle.

Carbon Cycle

The biogeochemical cycle that circulates carbon from the atmosphere through the food web via photosynthesis and consumer feeding, and back to the atmosphere via cellular respiration, decomposition, and combustion of fossil fuels.

Nitrogen Fixation

The chemical process primarily carried out underground by specialized bacteria—either living freely in the soil or in root nodules—that converts atmospheric nitrogen ($N_2$) into ammonia ($NH_3$) for plant uptake.

Phosphorus Cycle

The biogeochemical cycle that occurs at and below ground level without an atmospheric component, in which phosphate is released through the weathering of rocks, moves through the food web, and returns to soil and sediments via decomposition.