Evolution & Adaptation
60 mechanisms in this category
Adaptive Radiation
One ancestor. Eighteen species. Same genes. Radically different beaks. When Darwin collected finches on the Galápagos Islands in 1835, he documented n...
Background Extinction
Background extinction is the norm: species arise through speciation and disappear through extinction continuously. The average species lifespan is ~1-...
Co-Development Partnerships
Mycorrhizal fungi and plants engage in continuous co-development. As environmental conditions change - drought stress, nutrient fluctuations, pathogen...
Co-evolution
Co-evolution is reciprocal evolutionary change between interacting species, where each species is a selective pressure on the other. The environment i...
Convergent Evolution
Convergent evolution occurs when independent lineages evolve similar solutions to the same environmental problem. The camera eye evolved at least twic...
Diffuse Co-evolution
Many-on-many interaction where multiple species interact without single pairwise relationships dominating. Tropical ant-plant mutualisms illustrate th...
Disturbance Adaptation
Some species don't just survive disturbance - they require it. Lodgepole pine has serotinous cones that require fire heat to open and release seeds. C...
Early Burst Pattern
Adaptive radiations show rapid initial diversification - speciation rate is initially very high, then slows as niches fill. This creates a deceleratin...
Ecological Inheritance
Ecological inheritance is the transmission of modified environments across generations, distinct from genetic inheritance. An organism inherits not on...
Ecological Opportunity
Ecological opportunity - access to resources or environments that existing species aren't exploiting - triggers adaptive radiation through two primary...
Ecological Release
Ecological release occurs when colonizers radiate to fill roles occupied by specialists elsewhere. Without competitors, selection favors generalist po...
Ecosystem Engineering
Ecosystem engineers are organisms that modify their physical environment in ways that alter resource availability and selection pressures for themselv...
Effective Population Size
The effective population size (Ne) is the size of an ideal Wright-Fisher population that would experience the same amount of drift as the actual popul...
Escape-and-Radiate Co-evolution
Termed by Ehrlich and Raven (1964): plants 'escape' herbivory by evolving novel toxins, then radiate into new ecological niches (adaptive radiation)....
Evolutionary Arms Race
Cheetahs run at 110+ km/h. Thomson's gazelles hit 80+ km/h. Neither speed is 'optimal' in isolation - both are the product of millions of years of esc...
Evolutionary Tracking
On timescales longer than individual lifespans - centennial to millennial cycles - adaptation must be genetic. Large mammals adapted to Ice Age cycles...
Evolutionary Traps
Evolutionary traps occur when niche construction becomes maladaptive - the constructed environment ultimately harms the constructor. Moths evolved nav...
Evolvability
Evolvability - the capacity to produce heritable phenotypic variation - determines whether ecological opportunity translates into radiation. Two mecha...
Extinction Vortex
Once populations decline below critical thresholds, multiple factors interact to create extinction vortices - positive feedbacks that accelerate decli...
Fitness Landscape
The large ground finch's crushing beak is perfect for cracking hard seeds during drought. It's a liability during wet years when soft seeds are abunda...
Founder Effects
The Afrikaner population of South Africa has 10× higher rates of Huntington's disease than the global average. The Amish carry Ellis-van Creveld syndr...
Gene Flow
Gene flow is the movement of genetic variants between populations through migration and interbreeding. When individuals migrate from one population to...
Gene-Culture Coevolution
Gene-culture coevolution describes genetic changes driven by cultural practices. Dairy farming created a niche where lactose-tolerant adults (who reta...
Genetic Drift
Genetic drift represents one of evolution's most counterintuitive principles: random events can drive evolutionary change as powerfully as adaptive se...
Genetic Rescue
Genetic rescue occurs when gene flow from a larger population rescues a small, isolated population from genetic deterioration. Small populations suffe...
Geographic Mosaic Co-evolution
John Thompson's theory (1999): co-evolving species experience different selection pressures in different locations, creating a mosaic of local adaptat...
Historical Contingency
Historical contingency refers to the dependence of evolutionary outcomes on prior history. Some solutions are inaccessible to certain lineages due to...
Hormesis
You're at the gym. You're lifting weight that hurts. Your muscles are literally tearing - microscopic damage to muscle fibers visible under electron m...
Key Innovations
Key innovations create ecological opportunity by evolving traits that unlock access to previously unavailable resources - not through geographic movem...
Kin Selection
W.D. Hamilton's kin selection theory explains why organisms sacrifice for relatives. An individual's alarm call protects siblings, offspring, and rela...
Mass Extinction
Mass extinction is catastrophic: extinction rates spike to 10-100x background rates, and large fractions (>50-75%) of species disappear within geologi...
Metabolic Flexibility
Organisms can switch between metabolic pathways depending on circumstances. Sprinting? Use glycolysis. Resting? Use oxidative phosphorylation. Starvin...
Migration-Selection Balance
When populations inhabit different environments, local adaptation creates genetic differentiation. Migration between populations introduces maladaptiv...
Molecular Convergence
Convergence occurs not only at morphological and behavioral levels but also at molecular levels - different genetic mutations producing the same funct...
Muller's Ratchet
Species with small populations accumulate slightly deleterious mutations because drift overpowers the weak selection against them. This is called Mull...
Mutational Meltdown
The optimal mutation rate maximizes evolvability: high enough to generate useful variation, low enough to avoid mutational meltdown. Models suggest op...
Mutator Phenotype
In some contexts, natural selection favors mutators - organisms with higher-than-normal mutation rates due to defects in DNA repair or replication fid...
Mutualistic Co-evolution
Reciprocal adaptations that benefit both parties. Flowering plants and pollinators co-evolved: plants evolved nectar, bright colors, and floral shapes...
Natural Selection
Natural selection isn't a theory. It's mathematics. When four conditions exist simultaneously - variation, heritability, differential survival, and se...
Neutral Theory
Motoo Kimura's neutral theory (1968) proposed that most mutations at the molecular level are selectively neutral - they have no effect on fitness. The...
Niche Construction
Niche construction theory, formalized by evolutionary biologists Odling-Smee, Laland, and Feldman (2003), describes how organisms actively modify thei...
Outcome-Based Contracting
Legume plants don't pay nitrogen-fixing bacteria for showing up - they pay for nitrogen delivered. Plants monitor nodule performance with ruthless pre...
Pairwise Co-evolution
One-on-one reciprocal adaptation between two species. The yucca moth and yucca plant exemplify extreme pairwise co-evolution: yucca plants are pollina...
Parallel Evolution
Parallel evolution occurs when closely related lineages independently evolve similar traits from shared ancestral potential, as distinguished from con...
Phenotypic Plasticity
Same genes. Different body. Triggered by environmental cues. Phenotypic plasticity is adaptation within a lifetime - without waiting for genetic evolu...
Predation-Driven Life History
David Reznick's Trinidad guppy experiments (1990) demonstrated that energy allocation strategy evolves based on predation environment. High-predation...
Punctuated Equilibrium
Punctuated equilibrium is evolution's reminder that the future doesn't arrive gradually. For millions of years, nothing changes. Then everything chang...
Reciprocal Altruism
In species with long-term social relationships, individuals who call when they detect threats build reputations as vigilant, and others preferentially...
Red Queen Dynamics
Evolutionary arms races create 'Red Queen' dynamics (from Alice in Wonderland: 'it takes all the running you can do to stay in the same place'). Neith...
Red Queen Hypothesis
Imagine running at full sprint. Your muscles burn. Your lungs scream. You push harder, faster, desperate. But you're not gaining ground - you're just...
Reproductive Isolation
Adaptive radiation requires diverging populations to remain reproductively isolated - if they interbreed freely, gene flow homogenizes them, preventin...
Runaway Co-evolution
Arms races that escalate to extremes, producing traits far beyond what's optimal in isolation. Sexual selection creates runaway dynamics: female mate...
Selection Pressure
Selection pressures are environmental forces that favor some traits over others: predation, resource scarcity, temperature extremes. Strong selection...
Small-Population Vortex
Population declines due to extrinsic threat → small population causes inbreeding depression → reduced fitness causes further decline → stronger demogr...
Speciation
Speciation is the process by which populations diverge into separate species. Gene flow opposes speciation by homogenizing populations. Three modes ex...
Stem Cells
Stem cells are undifferentiated cells - they haven't committed to becoming a specific type yet. They're flexible, uncommitted, capable of becoming wha...
Stress-Induced Mutagenesis
Stress-induced mutagenesis demonstrates that mutation rates can increase dynamically in response to environmental stress. Under starvation or other st...
Sympatric Speciation
Sympatric speciation is the evolution of new species without geographic separation. In African cichlids, behavioral isolation via mate choice accelera...
TetrodotoxinResistance
Garter snakes evolved TTX resistance through specific mutations in voltage-gated sodium channels - the molecular target of TTX. These mutations involv...
The Dinosaur's Dilemma
Specialists are more extinction-prone than generalists because specialists depend on specific resources (food, habitat, climate). If those resources d...