Population Ecology
Number of individuals of a population per unit area or volume
Population Density
A species that exerts strong, pivotal control on community structure due to its critical ecological role—rather than because of its high abundance or biomass—is defined as a:
Keystone species
Living parts of an ecosystem like plants, animals, fungi, and bacteria that drive production, consumption, and decomposition.
Biotic Factors
When resources and space within the environment are unlimited, a population can experience this type of growth
Exponential Growth
In a food web containing phytoplankton → zooplankton → small fish → salmon → sea lions, which organism functions as a secondary consumer?
The small fish
The movement of solar energy through food chains, food webs, and trophic levels (from producers to consumers and decomposers).
Energy Flow
The maximum population size of a species that an environment can sustain indefinitely without permanently damaging or degrading its resources, usually indicated on a logistic growth curve when population growth levels out
Carrying Capacity (K)
Moderate levels of disturbance foster greater species diversity than either high or low levels of disturbance. This is known as the
Intermediate Disturbance Hypothesis
Which of the trophic groups is essential for returning chemical elements locked in dead organic matter back to abiotic reservoirs (soil, water, air)?
Decomposers
Production of numerous small offspring, early reproductive maturity, and minimal parental care are indicators of what type of species?
r-selected
Two species competing for the exact same limiting resources cannot coexist permanently in the same place. This is known as the
Competitive Exclusion Principle
The rate at which an ecosystem's producers convert solar energy into chemical energy minus the energy used for their own cellular respiration
Net Primary Production (NPP)
A severe late-spring frost kills 80% of the emerging fruit crop across an orchard, regardless of how many fruit trees are planted per acre. This mortality event is best classified as a:
Density-independent factor
The sum of a species' use of biotic (living) and abiotic (non-living) resources in its environment
This "Rule" explains why food chains are short (usually 4–5 levels) and why top carnivore populations are naturally small and vulnerable (N stays well below local K).
The 10% Rule