Ecology & Ecosystems
43 mechanisms in this category
10% Rule
~90% of energy is lost at each trophic level. When herbivores eat plants, only ~10% of the plant's energy converts to herbivore biomass - the rest is...
Allee Effect
Below critical density, populations can't find mates, cooperate for predator defense, or maintain social structures. This creates positive feedback to...
Alternative Stable States
Alternative stable states represent modern ecology's recognition that succession doesn't always converge on a single climax but can progress toward di...
Climax Community
A climax community is a stable, self-sustaining assemblage of species where composition changes slowly. Climax communities aren't 'better' than pionee...
Competitive Exclusion Principle
When two species compete for identical resources in identical ways, the superior competitor eventually drives the inferior one to extinction locally....
Decomposition
Decomposition is biological warfare and collaborative feast happening simultaneously. A fallen tree becomes battleground where thousands of species co...
Demographic Stochasticity
Random fluctuations in birth/death rates can crash small populations. If a population of 50 individuals happens to produce no offspring in one bad yea...
Ecological Redundancy
At the ecosystem level, redundancy manifests as functional redundancy - multiple species performing similar ecological roles. Multiple pollinator spec...
Ecological Succession
In 2015, a volcanic island named Hunga Tonga emerged from the Pacific. Scientists watched succession unfold in real time: Year 1, bare rock. Year 2, p...
Ecosystem Engineer
Ecosystem engineers are organisms that modify physical habitats, creating conditions that other species depend on. The beaver is the canonical example...
Ecosystem Engineering
Some species create physical structures that many other species depend on. These ecosystem engineers or keystone engineers have disproportionate impac...
Ecosystem Trophic Structure
Ecosystems exhibit modularity in their organization into trophic levels - groups of organisms occupying similar food web positions. Primary producers...
Environmental Modification
Pioneer species modify their environment in multiple ways that create conditions enabling successor species. Lichens secrete acids that weather rock,...
Facilitation
Hemlock seedlings planted on bare rock die. The same seedlings planted under alder canopy survive. The hemlocks haven't changed - the alders changed t...
Functional Response
Functional response describes how individual predator kill rates change with prey density. Three types exist: Type I (linear): Kill rate increases li...
Inbreeding Depression
The Florida panther was dying from within. By the 1990s, fewer than 30 individuals remained, isolated in South Florida for decades. The symptoms were...
Inhibition
Early species prevent later species from establishing while alive. Pioneer trees monopolize light - shade-tolerant seeds germinate but don't grow (wai...
Invasive Species
An invasive species is an organism introduced to an ecosystem where it has no natural predators, competitors, or diseases, experiencing ecological rel...
Island Biogeography
Islands represent ~1/6 of Earth's land area but contain outsized biological diversity. Two factors drive this: size and isolation. Size determines car...
Keystone Modification
Some species become keystones by modifying disturbance frequency, intensity, or extent - thereby controlling which other species can persist. Fire-ada...
Keystone Mutualism
Some species create disproportionate impact by providing services that connect or enable many other species. These keystone mutualists don't dominate...
Keystone Nutrient Provision
In nutrient-poor ecosystems, species that provide limiting nutrients become keystones. Their presence unlocks productivity for the entire community; t...
Keystone Predation
A keystone predator prevents competitive dominants from monopolizing resources, thereby maintaining diversity. Some species are superior competitors f...
Keystone Species
Remove a dominant species and the ecosystem adjusts. Remove a keystone species and the ecosystem collapses or transforms into something unrecognizable...
Keystone Species Dynamics
Keystone species have impacts far exceeding their biomass because they regulate interactions between other species. Sea otters in kelp forest ecosyste...
Mesopredator Release
In systems with top predators and smaller mesopredators (mid-level carnivores), top predators often suppress mesopredators through killing or intimida...
Metapopulation Dynamics
Metapopulations are networks of local populations connected by migration. Local populations periodically go extinct, and empty habitat patches are rec...
Niche Partitioning
Niche partitioning is specialization that allows multiple species to coexist by reducing direct competition. Species divide resources along dimensions...
Nitrogen Cycle
Nitrogen exemplifies nutrient cycling's complexity and importance. Nitrogen is essential for life - a primary constituent of amino acids, proteins, nu...
Numerical Response
Numerical response describes how predator population size changes with prey density through two mechanisms: Reproductive response: When prey are abun...
Nutrient Cycling
Nutrient cycling is the continuous movement of chemical elements through ecosystems. Elements flow from inorganic forms to organic compounds in living...
Overlapping Generations
Even short-lived species can buffer cycles if their populations contain overlapping generations - multiple age classes coexisting. Pacific salmon popu...
Phosphorus Cycle
There is no phosphorus in the atmosphere. None. Lose it, and it's gone. This stark reality makes phosphorus fundamentally different from nitrogen. Pho...
Pioneer Species
Pioneer species are the first colonizers in ecological succession. They tolerate harsh conditions - intense sun, no soil, high salinity, temperature e...
Population Cycling
The mathematical formalization of predator-prey dynamics began with Alfred Lotka and Vito Volterra in the 1920s. The Lotka-Volterra model describes ho...
Predator-Prey Dynamics
Predator-prey dynamics represent one of ecology's most fundamental regulatory mechanisms. Predators limit prey population growth, preventing overexplo...
Primary Succession
Primary succession begins on substrates never previously occupied by life - volcanic islands, glacial moraines, lava flows. No soil exists. No seeds....
Refugia
Prey populations persist despite predation partly through refugia - safe areas or times reducing predation risk: Physical refugia: Burrows, dense veg...
Secondary Succession
Mount St. Helens erupted in 1980, devastating 230 square miles of forest. The landscape looked dead - gray ash covering everything, trees flattened li...
Stoichiometric Constraints
Organisms require nutrients in specific ratios. Marine phytoplankton need carbon, nitrogen, and phosphorus (C:N:P) in approximate ratios of 106:16:1....
Trophic Cascades
Remove one species. Watch an entire ecosystem transform. Trophic cascades reveal that ecosystems - and organizations - are connected in ways that make...
Trophic Levels & Energy Flow
Ecosystems organize into trophic levels - feeding levels that define energy flow. Level 1 (Primary Producers): plants, 450 gigatons carbon. Level 2 (P...
Winner-Take-All Dynamics
The competitive exclusion principle in ecology states that when two species compete for identical resources in identical ways, the superior competitor...