Comprehensive University Study Notes on Evolutionary Biology, Ecology, and Global Biogeochemical Systems

A comprehensive vocabulary review deck spanning evolutionary selection mechanisms, speciation, phylogenetics, global climate drivers, biome characteristics, interspecific interactions, energy flow, and global biogeochemical cycles.

Directional Selection

A mode of natural selection where individuals at one phenotypic extreme have higher fitness, causing the mean phenotype to shift while phenotypic variation stays the same or decreases.

Stabilizing Selection

A mode of natural selection where individuals with intermediate traits (such as midsize beaks) have the highest fitness, reducing phenotypic variation in the population.

Disruptive Selection

A mode of natural selection where individuals with intermediate phenotypes have the lowest fitness and individuals at both opposite phenotypic extremes are favored, increasing overall phenotypic variation.

Phenotypic Plasticity

Changes that occur in an individual organism over the course of its lifespan in response to environmental conditions, which does not constitute evolution.

Fundamental Asymmetry of Sex

The evolutionary principle that females invest more energy into caring for and producing offspring than males (making eggs is more energetically costly than making sperm), resulting in distinct selection pressures between sexes.

Sexual Selection

A form of natural selection for traits that increase an individual's mating opportunities, typically acting strongly on males whose access to females is limited.

Sex-Reversed Mating System

A mating system in which males invest more energy into caring for offspring than females, as observed in male seahorses.

Intersexual Selection

A type of sexual selection where individuals of one sex choose mates of the opposite sex, often driving the evolution of showy traits in the chosen sex (female mate choice).

Sexual Dimorphism

A condition in which males and females of the same species exhibit distinctly different physical appearances and characteristics.

Honest Signals

Showy phenotypic traits exhibited by males that reliably communicate good physiological health and genetic quality to prospective female mates.

Runaway Selection

An evolutionary mechanism in which arbitrary male traits are reinforced and passed on to offspring purely due to female attraction rather than any inherent survival benefit.

Intrasexual Selection

A form of sexual selection involving direct competition between individuals of the same sex for access to mates, favoring traits that improve fighting or territorial competitive ability.

Species

A group of organisms that exchange genes with members of their own group and do not exchange genes with other groups.

Biological Species Concept

A species concept identifying species based on reproductive isolation; individuals belonging to distinct biological species cannot interbreed to produce viable, fertile offspring.

Morphological Species Concept

A species concept that identifies evolutionarily distinct lineages based entirely on differences in observable phenotypic traits, applicable to fossils and asexual organisms.

Polymorphic Species

A species containing individuals that look physically different from one another despite belonging to the same interbreeding gene pool.

Cryptic Species

Distinct species that share nearly identical physical morphology but cannot interbreed and are genetically differentiated.

Phylogenetic Species Concept

A species concept that identifies species based on their evolutionary history, defining a species as the smallest monophyletic group on a phylogenetic tree.

Hybrid

An individual organism resulting from interbreeding between parents of two different species.

Prezygotic Mechanisms

Reproductive isolating mechanisms that prevent mating or egg fertilization from ever taking place between different species.

Temporal Isolation

A prezygotic barrier where closely related species do not interbreed because they mate at different times of the day or seasons of the year.

Behavioral Isolation

A prezygotic barrier in which mating fails to occur because populations possess distinct courtship displays, songs, or dances.

Mechanical Isolation

A prezygotic barrier where mating is attempted but fails because the male and female reproductive structures are physically incompatible.

Gametic Isolation

A prezygotic barrier where gametes are exchanged or come into contact, but egg and sperm are chemically incompatible and fail to fertilize.

Postzygotic Mechanisms

Reproductive isolating barriers that occur after fertilization, resulting either in zygote developmental failure or in sterile adult offspring.

Hybrid Inviability

A postzygotic barrier where hybrid offspring do not develop properly in the embryonic or juvenile stages and die young.

Hybrid Sterility

A postzygotic barrier where hybrid offspring survive and mature successfully into adulthood but are completely sterile and unable to produce gametes.

Speciation

The evolutionary formation of new species, which occurs when gene flow between populations is reduced and populations differentiate via mutations, genetic drift, and natural selection.

Allopatric Speciation

Speciation that occurs when populations become geographically isolated from one another due to dispersal or physical vicariance events.

Vicariance

A physical splitting of a species' habitat by a geographical barrier (such as a river dividing a population) that prevents gene flow between isolated groups.

Sympatric Speciation

Speciation that occurs between populations inhabiting the same overlapping geographic area, driven by disruptive selection or changes in chromosome number.

Polyploidy

A condition involving changes in the number of chromosome sets, highly common in plants, leading to instant speciation because polyploids cannot successfully interbreed with diploid progenitors.

Macroevolution

Broad-scale evolutionary patterns and processes of speciation and diversification that shape global biodiversity over deep time.

Sister Taxa

Two or more taxa on a phylogenetic tree that share an immediate common ancestor and are each other's closest evolutionary relatives.

Outgroup

A taxon on a phylogenetic tree that diverged prior to the lineage containing the taxa of interest, used to establish the ancestral state and direction of evolutionary change.

Synapomorphy

A shared derived evolutionary trait present in an ancestral lineage and all its descendants, but not seen in more distant ancestors.

Monophyletic Group

A phylogenetic grouping (identified by 'one snip') consisting of a common ancestor and all of its evolutionary descendants.

Paraphyletic Group

A phylogenetic grouping that includes an ancestral taxon and some, but not all, of its evolutionary descendants.

Polyphyletic Group

A phylogenetic grouping comprising organisms that share similar physical or ecological traits but do not share an immediate common ancestor.

Greenhouse Gases

Molecules containing at least 3 atoms (such as $CO_2$ and methane) that absorb and emit solar radiation, making up less than $1\%$ of Earth's atmosphere.

Hadley Cell

A major global atmospheric circulation pattern where warm, moist air rises at the equator, drops heavy rain, and travels to $30^\circ$ latitude where it cools, sinks, warms up, and creates arid desert bands.

Ferrel Cell

A mid-latitude atmospheric circulation cell located around $60^\circ$ latitude, defined by trade winds and producing regions of low precipitation.

Polar Cell

An atmospheric circulation cell located around $90^\circ$ latitude where cold, dense air descends, generating very high atmospheric pressure and extremely dry conditions.

Seasonality

The degree of difference between summer and winter temperatures in a geographic region, which increases with higher latitudes and is produced by Earth's orbital tilt.

Rain Shadow

A dry geographic zone formed on the leeward side of a mountain range after moist onshore winds rise, cool, and release precipitation on the windward slopes.

Biome

A large-scale terrestrial ecological region characterized and defined by its dominant vegetation, which varies predictably based on temperature and precipitation across latitudes.

Arctic Tundra

A northern, high-latitude biome characterized by permanently frozen soils, very low temperatures, and low plant and animal diversity.

Boreal Forest

A high-latitude, cold biome dominated by conifer pine trees and snow, exhibiting lower species diversity than temperate zones.

Ecological Niche

The complete suite of environmental limits, resources, and conditions where a species can survive, grow, and reproduce; formalized by G. Evelyn Hutchinson as an $n$-dimensional hypervolume.

Fundamental Niche

The entire range of environmental conditions and physical resources an organism could theoretically occupy and tolerate in the complete absence of biotic limits or competition.

Realized Niche

The actual space, resources, and environmental conditions an organism occupies in the wild in the presence of biotic interactions; it can equal the fundamental niche but never exceed it.

Mutualism

An ecological interaction between two species where both participating species receive a fitness or survival benefit ($+, +$).

Commensalism

An ecological interaction where one species benefits from the relationship while the other species is neither harmed nor helped ($+, 0$).

Parasitism

A symbiotic interaction in which one organism (the parasite) feeds off of, harms, and reduces the fitness of a host organism ($+, -$).

Symbiosis

A close and prolonged physical association between organisms of two different species, which can encompass mutualisms, commensalisms, or obligatory parasitisms.

Competitive Exclusion

An ecological outcome stating that two species competing for the exact same limiting resources cannot stably coexist indefinitely, resulting in one species being eliminated.

Niche Partitioning

An evolutionary or behavioral shift where competing species divide limited resources or shift spatial and temporal usage, lowering competition and permitting stable coexistence.

Character Displacement

An evolutionary divergence in morphological traits between competing sympatric species that occurs to minimize niche overlap and resource competition.

Coevolution

A reciprocal evolutionary process where two interacting species mutually influence each other's adaptations; it occurs only in consumptive ($+, -$) or mutualistic ($+, +$) relationships, not commensalism.

Evolutionary Arms Race

A mechanism of coevolution occurring in consumptive ($+, -$) interactions characterized by continuous reciprocal adaptations between predators and prey just to maintain their relative fitness.

Keystone Species

A species that exerts a disproportionately strong structuring effect on its ecological community relative to its actual physical abundance or biomass.

Dominant Species

The most abundant species with the highest biomass in an ecological community that significantly impacts the community through its physical prevalence.

Ecosystem Engineers

Organisms (such as beavers or ants) that mechanically create, modify, or maintain physical habitats for other community members, often functioning as keystone species.

Gross Primary Productivity (GPP)

The total amount of chemical energy and glucose generated by primary producers via photosynthesis from solar energy.

Net Primary Productivity (NPP)

The fraction of gross primary productivity that remains after primary producers expend energy for cellular respiration ($55\%$), representing the biomass ($45\%$) available to primary consumers.

Biomagnification

The progressive ten-fold ($10\times$) increase in concentration of non-excretable environmental toxins and pollutants at each successively higher trophic level.

Bioaccumulation

The progressive build-up and retention of pollutants within the tissues of a single organism over the course of its lifespan because the toxins cannot be excreted.

Bottom-Up Control

An ecological community regulation model where abiotic variables, nutrient availability, and primary producers dictate the population abundance of all higher trophic levels.

Top-Down Control

An ecological community regulation model where top consumers and apex predators control the population size and diversity of lower trophic levels, frequently causing trophic cascades.

Biogeochemical Cycle

The continuous cyclical pathway that chemical elements follow as they move between abiotic environmental reservoirs, through living trophic levels, and back to abiotic systems.

Nitrogen Fixation

The chemical conversion of inert atmospheric dinitrogen ($N_2$) into bioavailable ammonium ($NH_4^+$) or aqueous forms ($NH_3$) that plants can assimilate into organic tissues.

Eutrophication

The influx of excess nitrogen and phosphorus into aquatic ecosystems, stimulating explosive algal and plant blooms that deplete dissolved oxygen ($O_2$) upon decomposition.