Ecology: Populations, Communities, and Ecosystems

Vocabulary flashcards covering ecological hierarchy, population dynamics, community interactions, biogeochemical cycles, aquatic ecosystems, and biomes.

Ecology

The study of how organisms interact with each other and their environment, and the distribution and abundance of organisms.

Biosphere

The collection of all biomes collectively, or all ecosystems on Earth.

Biomes

Major groupings of plants and animals that possess specific physical characteristics (e.g., deserts, tundras).

Ecosystem

A biological community together with the nonliving (abiotic) factors with which it interacts, driven by the flow of energy and cycling of elements.

Community

Populations of different species that live together in the same place.

Individualistic Concept

The view that a community is nothing more than an aggregation of species that happen to coexist in one place.

Holistic Concept

The view that communities function as an integrated unit.

Population

Individuals of the same species living together in a specific area.

Population Growth Rate

The difference between birth rate and death rate, corrected for any movement of individuals immigrating or emigrating from the population.

Exponential Growth

Innate, unchecked population growth occurring in unlimited environments, characterized by a J-shaped curve.

Logistic Growth

Population growth that slows and levels off as it approaches carrying capacity ($K$), producing an S-shaped (sigmoid) curve.

Carrying Capacity ($K$)

The maximum population size that a particular environment can support sustainably.

Density-Dependent Factors

Factors whose limiting impact increases as population density rises, such as competition, predation, disease, and hormones.

Density-Independent Factors

Environmental influences, such as weather and natural disasters, that limit populations regardless of their density.

$r$-Selected Adaptations

Life history traits favoring a high rate of increase ($r$), characterized by early reproduction, high offspring count, minimal parental care, and Type III survivorship (e.g., dandelions, insects, oysters).

k-selected adaptions

Life history traits favoring reproduction near carrying capacity ($K$), characterized by delayed reproduction, few offspring, extensive parental care, and Type I survivorship (e.g., whales, humans, elephants).

Demography

The statistical study of how big populations are and their structural characteristics.

Cohort

A group of individuals in a population that are of the same age.

Habitat

The physical place where an organism lives.

Niche

An organism's biological role, resource use, and pattern of living within a community.

Fundamental Niche

The entire potential range and biological role an organism could occupy in the absence of competition.

Realized Niche

The actual niche and range occupied by an organism when limited by interspecific interactions and competition.

Principle of Competitive Exclusion

The rule stating that if two species compete for the exact same limited resource, the species that uses it more efficiently will eventually eliminate the other locally.

Coevolution

Long-term, mutual evolutionary adjustments between interacting species over time.

Mutualism

A symbiotic relationship in which both participating species benefit ($+/+$), such as endosymbiosis.

Commensalism

A symbiotic relationship in which one species benefits while the other is unaffected ($+/0$).

Parasitism

A symbiotic relationship in which one organism benefits while harming the other ($+/-$).

Ecological Succession

The orderly, sequential replacement of one community by another from simple to complex structures over time.

Primary Succession

Ecological succession that initiates on bare rock or glacial deposits where no soil exists.

Secondary Succession

Ecological succession that follows a disturbance in an area where established soil is already present.

Net Primary Productivity

The total energy captured by photosynthesis minus energy lost to respiration ($NPP = GPP - R$), measured as biomass.

Biomass

The total weight of all organisms present in an ecosystem.

10% Rule

The thermodynamic principle stating that approximately $90\%$ of energy is lost as heat/metabolism at each trophic level, leaving only approximately $10\%$ to pass to the next level (with only $0.1\%$ reaching top carnivores from the sun).

Environmental Water Cycle

The physical portion of the water cycle where atmospheric water vapor undergoes condensation and evaporates without directly entering living organisms.

Organismic Water Cycle

The biological portion of the water cycle where water is absorbed by plants and released back to the atmosphere via sun-driven transpiration.

Aquifers

Underground rock or sediment layers containing groundwater, holding over $96\%$ of freshwater in the United States.

Nitrogen Fixation

The process whereby specialized bacteria convert stable atmospheric nitrogen gas ($N_2$), which comprises about $80\%$ of the atmosphere, into usable ammonia ($NH_3$).

Eutrophication

The process where excess nitrogen or phosphorus runoff triggers algal blooms, resulting in oxygen depletion and aquatic organism die-offs.

Elevation impact on Climate

The climatic pattern where temperature drops approximately $6^\circ\text{C}$ for every $1{,}000\,\text{m}$ gained in elevation, creating vertical ecological zonation.

Rain Shadow

A dry area on the leeward mountain side formed when moist air cools and precipitates on the windward side, leaving descending warm, dry air to produce desert conditions.

Tropical Rain Forest

The richest biome on Earth, displaying the highest species richness and biodiversity.

Savanna

A tropical grassland biome with sparse trees and seasonal rain where organism activity is concentrated during the rainy season.

Taiga

A northern conifer forest biome with dense evergreen trees, long cold winters, and minimal rainfall that occurs primarily in summer.

Tundra

An open, windswept, cold, and boggy northern biome characterized by permafrost (permanently frozen subsoil).

Chaparral

A Mediterranean-climate biome (e.g., California and Chile) dominated by evergreen shrubs that utilize fires to germinate seeds.

Desert

An inland terrestrial biome characterized by severe dryness, receiving less than $25\,\text{cm}$ of rain per year.

Littoral Zone

The shallow, edge region of a freshwater lake near the shore.

Limnetic Zone

The open-water surface area of a freshwater lake where light penetrates.

Profundal Zone

The deep-water zone of a freshwater lake beyond the reach of effective light penetration.

Oligotrophic Lake

A deep lake with scarce nutrients and organic matter, characterized by high dissolved oxygen ($O_2$) levels.

Eutrophic Lake

A shallow lake possessing an abundant supply of nutrients and organic matter, characterized by low dissolved oxygen ($O_2$).

Thermal Stratification

The division of a lake into distinct temperature layers, typically featuring warmer surface water and cooler deep water.

Estuary

A fertile coastal marine area where freshwater mixes with seawater, yielding intermediate salinity.

Open-Sea Surface

The upper pelagic layer of the ocean inhabited by plankton and fish, responsible for $40\%$ of all photosynthesis on Earth.