Appendix 5

Abundance The total number of individuals in a population that exist within a defined area.

Acclimation An environmentally induced change in an individual’s physiology.

Acid deposition Acids deposited as rain and snow or as gases and particles that attach to the surfaces of plants, soil, and water. Also known as Acid rain.

Acid rain See Acid deposition.

Acidity The concentration of hydrogen ions in a solution.

Active transport Movement of molecules or ions through a membrane against a concentration gradient.

Adaptation A characteristic of an organism that makes it well-suited to its environment.

Adiabatic cooling The cooling effect of reduced pressure on air as it rises higher in the atmosphere and expands.

Adiabatic heating The heating effect of increased pressure on air as it sinks toward the surface of Earth and decreases in volume.

Aestivation The shutting down of metabolic processes during the summer in response to hot or dry conditions.

Afrotropical region The biogeographic of the Southern Hemisphere that corresponds to most of Africa. Also known as Ethiopian region.

Age structure In a population, the proportion of individuals that occurs in different age classes.

Albedo The fraction of solar energy reflected by an object.

Algal bloom A rapid increase in the growth of algae in aquatic habitats, typically due to an influx of nutrients.

Allee effect See Positive density dependence.

Alleles Different forms of a particular gene.

Allochthonous Inputs of organic matter, such as leaves, that come from outside of an ecosystem.

Alpha diversity See Local diversity.

Alternative stable state When a community is disturbed so much that the species composition and relative abundance of populations in the community change, and the new community structure is resistant to further change.

Altruism A social interaction that increases the fitness of the recipient and decreases the fitness of the donor.

Anaerobic Without oxygen. Also known as Anoxic.

Annual An organism that has a life span of one year.

Anoxic See Anaerobic.

Aphotic zone The area of the neritic and oceanic zones where the water is so deep that sunlight cannot penetrate.

Aposematism See Warning coloration.

Area- and volume-based surveys Surveys that define the boundaries of an area or volume and then count all of the individuals in the space.

Artificial selection Selection in which humans decide which individuals will breed and the breeding is done with a preconceived goal for the traits of the population.

Asexual reproduction A reproduction mechanism in which progeny inherit DNA from a single parent.

Assimilated energy The portion of energy that a consumer digests and absorbs.

Assimilation efficiency The percentage of consumed energy that is assimilated.

Atmospheric convection currents The circulations of air between the surface of Earth and the atmosphere.

Australasian region The biogeographic of the Southern Hemisphere that corresponds to Australia, New Zealand, and New Guinea.

Autochthonous Inputs of organic matter that are produced by algae and aquatic plants inside an ecosystem.

Autotroph See Producer.

Basic metapopulation model A model that describes a scenario in which there are patches of suitable habitat embedded within a matrix of unsuitable habitat.

Batesian mimicry When palatable species evolve warning coloration that resembles unpalatable species.

Benthic zone The area consisting of the sediments at the bottoms of lakes, ponds, and oceans.

Beta diversity The number of species that differ in occurrence between two habitats.

Bicarbonate ion ( ) An anion formed by the dissociation of carbonic acid.

Binary fission Reproduction through duplication of genes followed by division of the cell into two identical cells.

Biomagnification The process by which the concentration of a contaminant increases as it moves up the food chain.

Biomass residence time The length of time that biomass spends in a given trophic level.

Biome A geographic region that contains communities composed of organisms with similar adaptations.

Biosphere All of the ecosystems on Earth.

Biosphere approach An approach to ecology concerned with the largest scale in the hierarchy of ecological systems, including movements of air and water—and the energy and chemical elements they contain—over Earth’s surface.

Biotic homogenization The process by which unique species compositions originally found in different regions slowly become more similar due to the movement of people, cargo, and species.

Blood shunting An adaptation that allows specific blood vessels to shut off so less of an animal’s warm blood flows to the cold extremities.

Boreal forest A biome densely populated by evergreen needle-leaved trees, with a short growing season and severe winters. Also known as Taiga.

Bottleneck effect A reduction of genetic diversity in a population due to a large reduction in population size.

Bottom-up control When the abundances of trophic groups in nature are determined by the amount of energy available from the producers in a community.

Boundary layer A region of unstirred air or water that surrounds the surface of an object.

C₃ photosynthesis The most common photosynthetic pathway, in which CO₂ is initially assimilated into a three- carbon compound, glyceraldehyde 3-phosphate (G3P).

C₄ photosynthesis A photosynthetic pathway in which CO₂ is initially assimilated into a four-carbon compound, oxaloacetic acid (OAA).

Carbonate ion (CO₃²⁻) An anion formed by the dissociation of carbonic acid.

Carrying capacity (K) The maximum population size that can be supported by the environment.

Caste Individuals within a social group sharing a specialized form of behavior.

Categorical variable A variable that falls into a distinct category or grouping. Also known as Nominal variable.

Cation exchange capacity The ability of a soil to retain cations.

Census Counting every individual in a population.

Central place foraging Foraging behavior in which acquired food is brought to a central place, such as a nest with young.

Chloroplasts Specialized cell organelles found in photosynthetic organisms.

Chromosomes Compact structures consisting of long strands of DNA that are wound around proteins.

Chronosequence A sequence of communities that exist over time at a given location.

Climate The typical atmospheric conditions that occur throughout the year, measured over many years.

Climate diagram A graph that plots the average monthly temperature and precipitation of a specific location on Earth.

Climax community The final seral stage in the process of succession.

Clones Individuals that descend asexually from the same parent and bear the same genotype.

Clustered dispersion A pattern of population dispersion in which individuals are aggregated in discrete groups.

Codominant When two alleles both contribute to the phenotype.

Coefficient of determination (R²) An index that tells us how well data fit to a line.

Coefficient of relatedness The numerical probability of an individual and its relatives carrying copies of the same genes from a recent common ancestor.

Coevolution When two or more species affect each other’s evolution.

Cohesion The mutual attraction among water molecules.

Cohesion–tension theory The mechanism of water movement from roots to leaves due to water cohesion and water tension.

Cohort life table A life table that follows a group of individuals born at the same time from birth to the death of the last individual.

Commensalism An interaction in which two species live in close association and one species receives a benefit while the other experiences neither a benefit nor a cost.

Community All populations of species living together in a particular area.

Community approach An approach to ecology that emphasizes the diversity and relative abundances of different kinds of organisms living together in the same place.

Community resilience The time it takes after a disturbance for a community to return to its original state.

Community resistance The amount that a community changes when acted upon by some disturbance, such as the addition or removal of a species.

Community stability The ability of a community to maintain a structure.

Competition An interaction with negative effects between two species that depend on the same limiting resource to survive, grow, and reproduce.

Concurrent circulation Movement of two fluids in the same direction on either side of a barrier through which heat or dissolved substances are exchanged.

Conduction The transfer of the kinetic energy of heat between substances that are in contact with one another.

Consumer An organism that obtains its energy from other organisms. Also known as a Heterotroph.

Consumption efficiency The percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level.

Continental drift The movement of landmasses across the surface of Earth.

Continuous variable A variable that can take on any numeric value, including values that are not whole numbers.

Control A manipulation that includes all aspects of an experiment except the factor of interest.

Convection The transfer of heat by the movement of liquids and gases.

Convergent evolution A phenomenon in which two species descended from unrelated ancestors look similar because they have evolved under similar selective forces.

Cooperation When the donor and the recipient of a social behavior both experience increased fitness from an interaction.

Coral bleaching Loss of color in corals as a result of the corals expelling their symbiotic algae.

Coral reef A marine biome found in warm, shallow waters that remain 20°C year-round.

Coriolis effect The deflection of an object’s path due to the rotation of Earth.

Correlation A statistical description of how one variable changes in relation to another variable.

Cosmopolitan Species with very large geographic ranges that can span several continents.

Cost of meiosis The 50 percent reduction in the number of a parent’s genes passed on to the next generation via sexual reproduction versus asexual reproduction.

Countercurrent circulation Movement of two fluids in opposite directions on either side of a barrier through which heat or dissolved substances are exchanged.

Crassulacean acid metabolism (CAM) A photosynthetic pathway in which the initial assimilation of carbon into a four-carbon compound occurs at night.

Creek See Stream.

Crypsis Camouflage that either allows an individual to match its environment or breaks up the outline of an individual to blend in better with the background environment.

Cultural eutrophication An increase in the productivity of aquatic ecosystems caused by human activities.

Cultural services Benefits of biodiversity that provide aesthetic, spiritual, or recreational value.

Damped oscillations A pattern of population growth in which the population initially oscillates but the magnitude of the oscillations declines over time.

Data See Observations.

Decomposer Organism that breaks down dead organic material into simpler elements and compounds that can be recycled through the ecosystem.

Delayed density dependence When density dependence occurs based on a population density at some time in the past.

Demographic stochasticity Variation in birth rates and death rates due to random differences among individuals.

Demography The study of populations.

Denitrification The process of converting nitrates into nitrogen gas.

Density In a population, the number of individuals per unit area or volume.

Density dependent Factors that affect population size in relation to the population’s density.

Density independent Factors that limit population size regardless of the population’s density.

Density-mediated indirect effect An indirect effect caused by changes in the density of an intermediate species.

Deoxyribonucleic acid (DNA) A molecule composed of two strands of nucleotides that are wound together into a shape known as a double helix.

Dependent variable A factor that is being changed.

Determinate growth A growth pattern in which an individual does not grow any more once it initiates reproduction.

Deterministic model A model that is designed to predict a result without accounting for random variation in population growth rate.

Detritivore An organism that feeds on dead organic matter and waste products that are collectively known as detritus.

Diapause A type of dormancy in insects that is associated with a period of unfavorable environmental conditions.

Die-off A substantial decline in density that typically goes well below the carrying capacity.

Dilution effect The reduced, or diluted, probability of predation to a single animal when it is in a group.

Dioecious Plants that contain either only male flowers or only female flowers on a single individual.

Direct effect An interaction between two species that does not involve other species.

Direct fitness The fitness that an individual gains by passing on copies of its genes to its offspring.

Direct selection Selection that favors direct fitness.

Directional selection When individuals with an extreme phenotype experience higher fitness than the average phenotype of the population.

Dispersal The movement of individuals from one area to another.

Dispersal limitation The absence of a population from suitable habitat because of barriers to dispersal.

Dispersion The spacing of individuals with respect to one another within the geographic range of a population.

Disruptive selection When individuals with either extreme phenotype experience higher fitness than individuals with an intermediate phenotype.

Dominance hierarchy A social ranking among individuals in a group, typically determined through contests such as fighting or other contests of strength or skill.

Dominant An allele that masks the expression of the other allele.

Donor The individual who directs a behavior toward another individual as part of a social interaction.

Dormancy A condition in which organisms dramatically reduce their metabolic processes.

Doubling time The time required for a population to double in size.

Dry climate A climate characterized by low precipitation and a wide range of temperatures, commonly found at approximately 30° N and 30° S latitudes.

Dynamic steady state When the gains and losses of ecological systems are in balance.

Ecological efficiency The percentage of net production from one trophic level compared to the next lower trophic level. Also known as Food chain efficiency.

Ecological envelope The range of ecological conditions that are predicted to be suitable for a species.

Ecological niche modeling The process of determining the suitable habitat conditions for a species.

Ecological stoichiometry The study of the balance of nutrients in ecological interactions, such as between an herbivore and a plant.

Ecological systems Biological entities that have their own internal processes and interact with their external surroundings.

Ecology The scientific study of the abundance and distribution of organisms in relation to other organisms and environmental conditions.

Ecosystem One or more communities of living organisms interacting with their nonliving physical and chemical environments.

Ecosystem approach An approach to ecology that emphasizes the storage and transfer of energy and matter, including the various chemical elements essential to life.

Ecotone A boundary created by sharp changes in environmental conditions over a relatively short distance, accompanied by a major change in the composition of species.

Ectoparasite A parasite that lives on the outside of an organism.

Ectotherm An organism with a body temperature that is largely determined by its external environment.

Egested energy The portion of consumed energy that is excreted or regurgitated.

El Niño–Southern Oscillation (ENSO) The periodic changes in winds and ocean currents in the South Pacific, causing weather changes throughout much of the world.

Electromagnetic radiation Energy from the Sun, packaged in small particle-like units called photons.

Emerging infectious disease A disease that is newly discovered, or has been rare and then suddenly increases in occurrence.

Endemic Species that live in a single, often isolated, location.

Endoparasite A parasite that lives inside an organism.

Endotherm An organism that can generate sufficient metabolic heat to raise body temperature higher than the external environment.

Energy residence time The length of time that energy spends in a given trophic level.

Energy-diversity hypothesis A hypothesis that sites with higher amounts of energy are able to support more species.

Environmental sex determination A process in which sex is determined largely by the environment.

Environmental stochasticity Variation in birth rates and death rates due to random changes in the environmental conditions.

Epilimnion The surface layer of the water in a lake or pond.

Epistasis When the expression of one gene is controlled by another gene.

Equilibrium isocline The population size of one species that causes the population of another species to be stable. Also known as Zero growth isocline.

Equilibrium theory of island biogeography A theory stating that the number of species on an island reflects a balance between the colonization of new species and the extinction of existing species.

Ethiopian region See Afrotropical region.

Eusocial A type of social animal in which individuals live in large groups with overlapping generations, cooperation in nest building and brood care, and reproductive dominance by one or a few individuals.

Eutrophication An increase in the productivity of aquatic ecosystems.

Evaporation The transformation of water from a liquid to a gaseous state with the input of heat energy.

Evenly spaced dispersion A pattern of dispersion of a population in which each individual maintains a uniform distance between itself and its neighbors.

Evolution Change in the genetic composition of a population over time.

Experimental unit The object to which we apply an experimental manipulation.

Exponential growth model A model of population growth in which the population increases continuously at an exponential rate.

Extra-pair copulations When an individual that has a social bond with a mate also breeds with other individuals.

Facilitation A mechanism of succession in which the presence of one species increases the probability that a second species can become established.

Fall bloom A rapid increase in the population of phytoplankton in fall that occurs with the infusion of nutrients from fall overturn.

Fall overturn The vertical mixing of lake water that occurs in fall, assisted by winds that drive the surface currents.

Fecundity The number of offspring produced by an organism per reproductive episode.

Field capacity The maximum amount of water held by soil particles against the force of gravity.

Fire-maintained climax community A successional stage that persists as the final seral stage due to periodic fires.

First law of thermodynamics Energy cannot be created or destroyed; it can only change form. Also known as the Law of conservation of energy.

Fitness The survival and reproduction of an individual.

Food chain A linear representation of how different species in a community feed on each other.

Food chain efficiency See Ecological efficiency.

Food web A complex and realistic representation of how species feed on each other in a community.

Founder effect When a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation.

Frequency-dependent selection When the rarer phenotype in a population is favored by natural selection.

Freshwater wetland An aquatic biome that contains standing fresh water, or soils saturated with fresh water for at least part of the year, and which is shallow enough to have emergent vegetation throughout all depths.

Functional response The relationship between the density of prey and an individual predator’s rate of food consumption.

Fundamental niche The range of abiotic conditions under which species can persist.

Gamma diversity See Regional diversity.

Gene pool The collection of alleles from all individuals in a population.

Generation time (T) The average time between the birth of an individual and the birth of its offspring.

Genetic drift A process that occurs when genetic variation is lost because of random variation in mating, mortality, fecundity, and inheritance.

Genotype The set of genes an organism carries.

Geographic range A measure of the total area covered by a population.

Geometric growth model A model of population growth that compares population sizes at regular time intervals.

Global climate change A phenomenon that refers to changes in Earth’s climates including global warming, changes in the global distribution of precipitation and temperature, changes in the intensity of storms, and altered ocean circulation.

Glycerol A chemical that prevents the hydrogen bonds of water from coming together to form ice unless the temperatures are well below freezing.

Glycoproteins A group of compounds that can be used to lower the freezing temperature of water.

Gonads The primary sexual organs in animals.

Gondwana The southern landmass that separated from Pangaea about 150 Mya and subsequently split into South America, Africa, Antarctica, Australia, and India.

Good genes hypothesis The hypothesis that an individual chooses a mate that possesses a superior genotype.

Good health hypothesis The hypothesis that an individual chooses the healthiest mates.

Grazer-maintained climax community When a successional stage persists as the final seral stage due to intense grazing.

Greenhouse effect The process of solar radiation striking Earth, being converted to infrared radiation and being absorbed and re-emitted by atmospheric gases.

Greenhouse gases Compounds in the atmosphere that absorb the infrared heat energy emitted by Earth and then emit some of the energy back toward Earth.

Gross primary productivity (GPP) The rate at which energy is captured and assimilated by producers in an area.

Growing season The months in a location that are warm enough to allow plant growth.

Growth rate In a population, the number of new individuals that are produced in a given amount of time minus the number of individuals that die.

Guild Within a given trophic level, a group of species that feeds on similar items.

Gyre A large-scale water circulation pattern between continents.

Habitat The place, or physical setting, in which an organism lives.

Habitat corridor A strip of favorable habitat located between two large patches of habitat that facilitates dispersal.

Habitat fragmentation The process of breaking up large habitats into a number of smaller habitats.

Hadley cells The two circulation cells of air between the equator and 30° N and 30° S latitudes.

Half-life The time required for a chemical to break down to half of its original concentration.

Handling time The amount of time that a predator takes to consume a captured prey.

Haplodiploid A sex-determination system in which one sex is haploid and the other sex is diploid.

Herbivore An organism that consumes producers such as plants and algae.

Heritability The proportion of the total phenotypic variation that is caused by genetic variation.

Hermaphrodite An individual that produces both male and female gametes.

Heterotroph See Consumer.

Heterozygous When an individual has two different alleles of a particular gene.

Hibernation A type of dormancy that occurs in mammals in which individuals reduce the energetic costs of being active by lowering their heart rate and decreasing their body temperature.

Homeostasis An organism’s ability to maintain constant internal conditions in the face of a varying external environment.

Homeotherm An organism that maintains constant temperature conditions within its cells.

Homozygous When an individual has two identical alleles of a particular gene.

Horizon A distinct layer of soil.

Horizontal transmission When a parasite moves between individuals other than parents and their offspring.

Hydrologic cycle The movement of water through ecosystems and atmosphere.

Hyperosmotic When an organism has a higher solute concentration in its tissues than the surrounding water.

Hypolimnion The deeper layer of water in a lake or pond.

Hyposmotic When an organism has a lower solute concentration in its tissues than the surrounding water.

Hypothesis An idea that potentially explains a repeated observation.

Ideal free distribution When individuals distribute themselves among different habitats in a way that allows them to have the same per capita benefit.

Inbreeding depression The decrease in fitness caused by matings between close relatives due to offspring inheriting deleterious alleles from both the egg and the sperm.

Inclusive fitness The sum of direct fitness and indirect fitness.

Independent communities Communities in which species do not depend on each other to exist.

Independent variable A factor that causes other variables to change.

Indeterminate growth A growth pattern in which an individual continues to grow after it initiates reproduction.

Indirect effect An interaction between two species that involves one or more intermediate species.

Indirect fitness The fitness that an individual gains by helping relatives pass on copies of their genes.

Indirect selection Selection that favors indirect fitness. Also known as Kin selection.

Individual A living being; the most fundamental unit of ecology.

Individual approach An approach to ecology that emphasizes the way in which an individual’s morphology, physiology, and behavior enable it to survive in its environment.

Indomalayan region The biogeographic of the Southern Hemisphere that corresponds to India and Southeast Asia. Also known as Oriental region.

Industrial melanism A phenomenon in which industrial activities cause habitats to become darker due to pollution and, as a result, individuals possessing darker phenotypes are favored by selection.

Infection resistance The ability of a host to prevent an infection from occurring.

Infection tolerance The ability of a host to minimize the harm that an infection can cause.

Inflection point The point on a sigmoidal growth curve at which the population achieves its highest growth rate.

Inhibition A mechanism of succession in which one species decreases the probability that a second species will become established.

Instrumental value of biodiversity A focus on the economic value a species can provide.

Interdependent communities Communities in which species depend on each other to exist.

Intermediate disturbance hypothesis The hypothesis that more species are present in a community that occasionally experiences disturbances than in a community that experiences frequent or rare disturbances.

Intertidal zone A biome consisting of the narrow band of coastline between the levels of high tide and low tide.

Intertropical convergence zone (ITCZ) The area where the two Hadley cells converge and cause large amounts of precipitation.

Intrinsic growth rate (r) The highest possible per capita growth rate for a population.

Intrinsic value of biodiversity A focus on the inherent value of a species, not tied to any economic benefit.

Inverse density dependence See Positive density dependence.

Ions Atoms or groups of atoms that are electrically charged.

Isozymes Different forms of an enzyme that catalyze a given reaction.

Iteroparity When organisms reproduce multiple times during their life.

Joint equilibrium point The point at which the equilibrium isoclines for predator and prey populations cross.

Joint population trajectory The simultaneous trajectory of predator and prey populations.

J-shaped curve The shape of exponential growth when graphed.

Keystone species A species that substantially affects the structure of communities despite the fact that individuals of that species might not be particularly numerous.

Kin selection See Indirect selection.

Lake An aquatic biome that is larger than a pond and is characterized by nonflowing fresh water with some area of water that is too deep for plants to rise above the water’s surface.

Landscape ecology The field of study that considers the spatial arrangement of habitats at different scales and examines how they influence individuals, populations, communities, and ecosystems.

Landscape metapopulation model A population model that considers both differences in the quality of the suitable patches and the quality of the surrounding matrix.

Latent heat release When water vapor is converted back to liquid, water releases energy in the form of heat.

Laterization The breakdown of clay particles, which results in the leaching of silicon from the soil, leaving oxides of iron and aluminum to predominate throughout the soil profile.

Laurasia The northern landmass that separated from Pangaea about 150 Mya and subsequently split into North America, Europe, and Asia.

Law of conservation of energy See First law of thermodynamics.

Law of conservation of matter Matter cannot be created or destroyed; it can only change form.

Leaching A process in which groundwater removes some substances by dissolving them and moving them down through the soil to lower layers.

Legacy effect A long-lasting influence of historical processes on the current ecology of an area.

Lek The location of an animal aggregation to put on a display to attract the opposite sex.

Life expectancy See Longevity.

Life history The schedule of an organism’s growth, development, reproduction, and survival.

Life tables Tables that contain class-specific survival and fecundity data.

Lifetime dispersal distance The average distance an individual moves from where it was hatched or born to where it reproduces.

Limnetic zone The open water beyond the littoral zone, where the dominant photosynthetic organisms are floating algae. Also known as the Pelagic zone.

Line-transect surveys Surveys that count the number of individuals observed as one moves along a line.

Littoral zone The shallow area around the edge of a lake or pond containing rooted vegetation.

Local diversity The number of species in a relatively small area of homogeneous habitat, such as a stream. Also known as Alpha diversity.

Local mate competition When competition for mates occurs in a very limited area and only a few males are required to fertilize all of the females.

Logistic growth model A growth model that describes slowing growth of populations at high densities.

Log-normal distribution A normal, or bell-shaped, distribution that uses a logarithmic scale on the x-axis.

Longevity The life span of an organism. Also known as Life expectancy.

Lotic Characterized by flowing fresh water.

Lotka-Volterra model A model of predator–prey interactions that incorporates oscillations in the abundances of predator and prey populations and shows predator numbers lagging behind those of their prey.

Macroevolution Evolution at higher levels of organization including species, genera, families, orders, and phyla.

Mangrove swamp A biome that occurs along tropical and subtropical coasts, and contains salt-tolerant trees with roots submerged in water.

Manipulation The factor that we want to vary in an experiment. Also known as a Treatment.

Manipulative experiment A process by which a hypothesis is tested by altering a factor that is hypothesized to be an underlying cause of the phenomenon.

Mark-recapture survey A method of population estimation in which researchers capture and mark a subset of a population from an area, return it to the area, and then capture a second sample of the population after some time has passed.

Mass extinction events Events in which at least 75% of the existing species go extinct within a 2 million-year period.

Mate guarding A behavior in which one partner prevents the other partner from participating in extra-pair copulations.

Mathematical model A representation of a system with a set of equations that correspond to hypothesized relationships among the system’s components.

Mating system The number of mates each individual has and the permanence of the relationship with those mates.

Matric potential The potential energy generated by the attractive forces between water molecules and soil particles. Also known as Matrix potential.

Matrix potential See Matric potential.

Mesopredators Relatively small carnivores that consume herbivores.

Microcosm A simplified ecological system that attempts to replicate the essential features of an ecological system in a laboratory or field setting.

Microevolution The evolution of populations.

Microhabitat A specific location within a habitat that typically differs in environmental conditions from other parts of the habitat.

Mineralization The process of breaking down organic compounds into inorganic compounds.

Minimum viable population (MVP) The smallest population size of a species that can persist in the face of environmental variation.

Mixotroph An organism that obtains its energy from more than one source.

Moist continental mid-latitude climate A climate that exists at the interior of continents and is typically characterized by warm summers, cold winters, and moderate amounts of precipitation.

Moist subtropical mid-latitude climate A climate characterized by warm, dry summers and cold, wet winters.

Monoecious Plants that have separate male and female flowers on the same individual.

Monogamy A mating system in which a social bond between one male and one female persists through the period that is required for them to rear their offspring.

Müllerian mimicry When several unpalatable species evolve a similar pattern of warning coloration.

Mutation A random change in the sequence of nucleotides in regions of DNA that either comprise a gene or control the expression of a gene.

Mutualism An interaction between two species in which each species receives benefits from the other.

Natural experiment An approach to hypothesis testing that relies on natural variation in the environment.

Natural selection Change in the frequency of genes in a population through differential survival and reproduction of individuals that possess certain phenotypes.

Nearctic region The biogeographic of the Northern Hemisphere that roughly corresponds to North America.

Negative density dependence When the rate of population growth decreases as population density increases.

Negative feedbacks The action of internal response mechanisms that restores a system to a desired state, or set point, when the system deviates from that state.

Neotropical region The biogeographic of the Southern Hemisphere that corresponds to South America.

Neritic zone The ocean zone beyond the range of the lowest tidal level, and which extends to depths of about 200 m.

Net primary productivity (NPP) The rate of energy that is assimilated by producers and converted into producer biomass in an area.

Net production efficiency The percentage of assimilated energy that is used for growth and reproduction.

Net reproductive rate The total number of female offspring that we expect an average female to produce over the course of her life.

Net secondary productivity The rate of consumer biomass accumulation in a given area.

Niche The range of abiotic and biotic conditions that an organism can tolerate.

Nitrification The final process in the nitrogen cycle, which converts ammonium to nitrite (NO₂) and then from nitrite to nitrate (NO₃⁻).

Nitrogen fixation The process of converting atmospheric nitrogen into forms producers can use.

Nominal variable See Categorical variable.

Numerical response A change in the number of predators through population growth or population movement due to immigration or emigration.

Observations Information, including measurements, that is collected from organisms or the environment. Also known as Data.

Oceanic zone The ocean zone beyond the neritic zone.

Omnivore A species that feeds at several trophic levels.

Optimum The narrow range of environmental conditions to which an organism is best suited.

Oriental region See Indomalayan region.

Osmoregulation The mechanisms that organisms use to maintain proper solute balance.

Osmosis The movement of water across a semipermeable membrane.

Osmotic potential The force with which an aqueous solution attracts water by osmosis.

Overshoot When a population grows beyond its carrying capacity.

Palearctic region The biogeographic of the Northern Hemisphere that corresponds to Eurasia.

Pangaea The single landmass that existed on Earth about 250 Mya and subsequently split into Laurasia and Gondwana.

Parasite An organism that lives in or on another organism, but rarely kills it.

Parasite load The number of parasites of a given species that an individual host can harbor.

Parasitoid An organism that lives within and consumes the tissues of a living host, eventually killing the host.

Parent material The layer of bedrock that underlies soil and plays a major role in determining the type of soil that will form above it.

Parental investment The amount of time and energy given to an offspring by its parents.

Parity The number of reproductive episodes an organism experiences.

Parthenogenesis A form of asexual reproduction in which an embryo is produced without fertilization.

Pathogen A parasite that causes disease in its host.

Pelagic zone See Limnetic zone.

Perennial An organism that has a life span of more than one year.

Perfect flowers Flowers that contain both male and female parts.

Permafrost A phenomenon where layers of soil are permanently frozen.

pH A measure of acidity or alkalinity; defined as pH = –log (H+ concentration).

Phenotype An attribute of an organism, such as its behavior, morphology, or physiology.

Phenotypic plasticity The ability of a single genotype to produce multiple phenotypes.

Phenotypic trade-off A situation in which a given phenotype experiences higher fitness in one environment whereas other phenotypes experience higher fitness in other environments.

Photic zone The area of the neritic and oceanic zones that contains sufficient light for photosynthesis by algae.

Photoperiod The amount of light that occurs each day.

Photorespiration The oxidation of carbohydrates to CO₂ and H₂O by Rubisco, which reverses the light reactions of photosynthesis.

Photosynthetically active region Wavelengths of light that are suitable for photosynthesis.

Phylogenetic trees Hypothesized patterns of relatedness among different groups such as populations, species, or genera.

Pioneer species The earliest species to arrive at a site.

Pleiotropy When a single gene affects multiple traits.

Podsolization A process occurring in acidic soils typical of cool, moist regions, where clay particles break down in the E horizon, and their soluble ions are transported down to the lower B horizon.

Poikilotherm An organism that does not have constant body temperatures.

Polar cells The atmospheric convection currents that move air between 60° and 90° latitudes in the Northern and Southern Hemispheres.

Polar climate A climate that experiences very cold temperatures and relatively little precipitation.

Polyandry A mating system in which a female mates with more than one male.

Polygamy A mating system in which a single individual of one sex forms long-term social bonds with more than one individual of the opposite sex.

Polygenic When a single trait is affected by several genes.

Polygyny A mating system in which a male mates with more than one female.

Polyploid A species that contains three or more sets of chromosomes.

Pond An aquatic biome that is smaller than a lake and is characterized by nonflowing fresh water with some area of water that is too deep for plants to rise above the water’s surface.

Population The individuals of the same species living in a particular area.

Population approach An approach to ecology that emphasizes variation over time and space in the number of individuals, the density of individuals, and the composition of individuals.

Population cycles Regular oscillation of a population over a longer period of time.

Positive density dependence When the rate of population growth increases as population density increases. Also known as Inverse density dependence or the Allee effect.

Potential evapotranspiration (PET) The amount of water that could be evaporated from the soil and transpired by plants, given the average temperature and humidity.

Predator An organism that kills and partially or entirely consumes another individual.

Prediction A logical consequence of a hypothesis.

Primary consumer A species that eats producers.

Primary productivity The rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis.

Primary sexual characteristics Traits related to fertilization.

Primary succession The development of communities in habitats that are initially devoid of plants and organic soil, such as sand dunes, lava flows, and bare rock.

Principle of allocation The observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another.

Priority effect When the arrival of one species at a site affects the subsequent colonization of other species.

Producer An organism that uses photosynthesis to convert solar energy into organic compounds or uses chemosynthesis to convert chemical energy into organic compounds. Also known as an Autotroph.

Profundal zone The area in a lake that is too deep to receive sunlight.

Promiscuity A mating system in which males mate with multiple females and females mate with multiple males and do not create a lasting social bond.

Provisioning services Benefits of biodiversity that humans use, including lumber, fur, meat, crops, water, and fiber.

Proximate hypothesis A hypothesis that addresses the immediate changes in an organism’s hormones, physiology, nervous system, or muscular system.

Pyramid of biomass A trophic pyramid that represents the standing crop of organisms present in different trophic groups.

Pyramid of energy A trophic pyramid that displays the total energy existing at each trophic level.

Q₁₀ The ratio of the rate of a physiological process at one temperature to its rate at a temperature 10°C cooler.

Queen The dominant, egg-laying female in eusocial insect societies.

Radiation The emission of electromagnetic energy by a surface.

Rain shadow A region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation on the windward side.

Random assortment The process of making haploid gametes in which the combination of alleles that are placed into a given gamete could be any combination of those possessed by the diploid parent.

Random dispersion A pattern of dispersion of a population in which the position of each individual is independent of the position of other individuals in the population.

Randomization An aspect of experiment design in which every experimental unit has an equal chance of being assigned to a particular manipulation.

Rank-abundance curve A curve that plots the relative abundance of each species in a community in rank order from the most abundant species to the least abundant species.

Realized niche The range of abiotic and biotic conditions under which a species persists.

Recessive An allele whose expression is masked by the presence of another allele.

Recipient The individual who receives the behavior of a donor in a social interaction.

Recombination The reshuffling of genes that can occur as DNA is copied during meiosis and chromosomes exchange genetic material.

Red Queen hypothesis The hypothesis that sexual selection allows hosts to evolve at a rate that can counter the rapid evolution of parasites.

Regional diversity The number of species in all of the habitats that comprise a large geographic area. Also known as Gamma diversity.

Regional species pool The collection of species that occurs within a region.

Regression A statistical tool that determines whether there is a relationship between two variables and that also describes the nature of that relationship.

Regulating services Benefits of biodiversity that include climate regulation, flood control, and water purification.

Relative abundance The proportion of individuals in a community represented by each species.

Remote sensing A technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.

Replication Being able to produce a similar outcome multiple times.

Rescue effect When dispersers supplement a declining subpopulation and thereby prevent the subpopulation from going extinct.

Reservoir species Species that can carry a parasite but do not succumb to the disease that the parasite causes in other species.

Respired energy The portion of assimilated energy a consumer uses for respiration.

Riparian zone A band of terrestrial vegetation alongside rivers and streams that is influenced by seasonal flooding and elevated water tables.

Risk-sensitive foraging Foraging behavior that is influenced by the presence of predators.

River A wide channel of slow flowing fresh water.

Root pressure When osmotic potential in the roots of a plant draws in water from the soil and forces it into the xylem elements.

Rubisco See RuBP carboxylase-oxidase.

RuBP carboxylase-oxidase An enzyme involved in photosynthesis that catalyzes the reaction of RuBP and CO₂ to form two molecules of glyceraldehyde 3-phosphate (G3P). Also known as Rubisco.

Runaway sexual selection When selection for preference of a sexual trait and selection for that trait continue to reinforce each other.

Salinization The process of repeated irrigation, which causes increased soil salinity.

Salt marsh A saltwater biome that contains nonwoody emergent vegetation.

Sample standard deviation A statistic that provides a standardized way of measuring how widely data are spread from the mean.

Sample variance A measurement that indicates the spread of the data around the mean of a population when only a sample of the population has been measured.

Saturation The upper limit of solubility in water.

Saturation point The limit of the amount of water vapor the air can contain.

Scavenger An organism that consumes dead animals.

Sclerophyllous Vegetation that has small, durable leaves.

Search image A learned mental image that helps the predator locate and capture food.

Secondary consumer A species that eats primary consumers.

Secondary sexual characteristics Traits related to differences between the sexes in terms of body size, ornaments, color, and courtship.

Secondary succession The development of communities in habitats that have been disturbed and contain no plants but still contain an organic soil.

Selection The process by which certain phenotypes are favored to survive and reproduce over other phenotypes.

Selfishness When the donor of a social behavior experiences increased fitness and the recipient experiences decreased fitness.

Self-thinning curve A graphical relationship that shows how decreases in population density over time lead to increases in the size of each individual in the population.

Semelparity When organisms reproduce only once during their life.

Semipermeable membrane A membrane that allows only particular molecules to pass through.

Senescence A gradual decrease in fecundity and an increase in the probability of mortality.

Sequential hermaphrodites Individuals that possess male or female reproductive function and then switch to possess the other function.

Seral stage Each stage of community change during the process of succession.

Sexual dimorphism The difference in the phenotype between males and females of the same species.

Sexual reproduction A reproduction mechanism in which progeny inherit DNA from two parents.

Sexual selection Natural selection for sex-specific traits that are related to reproduction.

Shannon’s index (H′) A measurement of species diversity, given by the following formula:

Also known as Shannon-Wiener index.

Shannon-Wiener index See Shannon’s index.

Simpson’s index A measurement of species diversity, given by the following formula:

Simultaneous hermaphrodites Individuals that possess male and female reproductive functions at the same time.

Sink subpopulations In low-quality habitats, subpopulations that rely on outside dispersers to maintain the subpopulation within a metapopulation.

Social behaviors Interactions with members of one’s own species, including mates, offspring, other relatives, and unrelated individuals.

Soil The layer of chemically and biologically altered material that overlies bedrock or other unaltered material at Earth’s surface.

Solar equator The latitude receiving the most direct rays of the Sun.

Solute A dissolved substance.

Source subpopulations In high-quality habitats, subpopulations that serve as a source of dispersers within a metapopulation.

Source–sink metapopulation model A population model that builds upon the basic metapopulation model and accounts for the fact that not all patches of suitable habitat are of equal quality.

Spatial structure The pattern of density and spacing of individuals in a population.

Speciation The evolution of new species.

Species Historically defined as a group of organisms that naturally interbreed with each other and produce fertile offspring. Current research demonstrates that no single definition can be applied to all organisms.

Species accumulation curve A graph of the number of species observed in relation to the number of individuals sampled.

Species evenness A comparison of the relative abundance of each species in a community.

Species richness The number of species in a community.

Species sorting The process of sorting species in the regional pool among localities according to their adaptations and interactions.

Species-area curve A graphical relationship in which increases in area (A) are associated with increases in the number of species (S).

Spitefulness When a social interaction reduces the fitness of both donor and recipient.

Spring overturn The vertical mixing of lake water that occurs in early spring, assisted by winds that drive the surface currents.

S-shaped curve The shape of the curve when a population is graphed over time using the logistic growth model.

Stabilizing selection When individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes.

Stable age distribution When the age structure of a population does not change over time.

Stable limit cycle A pattern of population growth in which the population continues to exhibit large oscillations over time.

Standard error of the mean A measurement of variation in data that takes into account the number of replicates that were used to measure the standard deviation.

Standing crop The biomass of producers present in a given area of an ecosystem at a particular moment in time.

Static life table A life table that quantifies the survival and fecundity of all individuals in a population during a single time interval.

Stepping stones Small intervening habitat patches that dispersing organisms can use to move between large favorable habitats.

Stochastic model A model that incorporates random variation in population growth rate.

Stomata Small openings on the surface of leaves, which serve as the points of entry for CO₂ and exit points for water vapor.

Stratification The condition of a lake or pond when the warmer, less dense surface water floats on the cooler, denser water below.

Stream A narrow channel of fast flowing fresh water. Also known as a Creek.

Strength of selection The difference between the mean of the phenotypic distribution before selection and the mean after selection, measured in units of standard deviations.

Subpopulations When a larger population is broken up into smaller groups that live in isolated patches.

Subtropical desert A biome characterized by hot temperatures, scarce rainfall, long growing seasons, and sparse vegetation.

Succession The process by which the species composition of a community changes over time.

Supercooling A process in which glycoproteins in the blood impede ice formation by coating any ice crystals that begin to form.

Supporting services Functions that allow ecosystems to exist.

Survey Counting a subset of the population.

Susceptible-Infected-Resistant (S-I-R) model The simplest model of infectious disease transmission that incorporates immunity.

Symbiotic relationship When two different types of organisms live in a close physical relationship.

Taiga See Boreal forest.

Temperate grassland/cold desert A biome characterized by hot, dry summers and cold, harsh winters and dominated by grasses, nonwoody flowering plants, and drought-adapted shrubs.

Temperate rainforest A biome known for mild temperatures and abundant precipitation, and dominated by evergreen forests.

Temperate seasonal forest A biome with moderate temperature and precipitation conditions, dominated by deciduous trees.

Territory Any area defended by one or more individuals against the intrusion of others.

Tertiary consumer A species that eats secondary consumers.

The handicap principle The principle that the greater the handicap an individual carries, the greater its ability must be to offset that handicap.

Thermal inertia The resistance to a change in temperature due to a large body volume.

Thermal optimum The range of temperatures within which organisms perform best.

Thermal pollution Discharging water that is too hot to sustain aquatic species.

Thermocline A middle depth of water in a lake or pond that experiences a rapid change in temperature over a relatively short distance in depth.

Thermohaline circulation A global pattern of surface- and deepwater currents that flow as a result of variations in temperature and salinity that change the density of water.

Thermophilic Heat-loving.

Thermoregulation The ability of an organism to control the temperature of its body.

Tolerance A mechanism of succession in which the probability that a species can become established depends on its dispersal ability and its ability to persist under the physical conditions of the environment.

Top predators Predators that typically consume both herbivores and mesopredators.

Top-down control When the abundance of trophic groups is determined by the existence of predators at the top of the food web.

Torpor A brief period of dormancy that occurs in birds and mammals in which individuals reduce their activity and their body temperature.

Trait-mediated indirect effect An indirect effect caused by changes in the traits of an intermediate species.

Transient climax community A climax community that is not persistent.

Transpiration The process by which leaves can generate water potential as water evaporates from the surfaces of leaf cells into the air spaces within the leaves.

Treatment See Manipulation.

Trophic cascade Indirect effects in a community that are initiated by a predator.

Trophic level A level in a food chain or food web of an ecosystem.

Trophic pyramid A chart composed of stacked rectangles representing the amount of energy or biomass in each trophic group.

Tropical climate A climate characterized by warm temperatures and high precipitation, occurring in regions near the equator.

Tropical rainforest A warm and rainy biome, characterized by multiple layers of lush vegetation.

Tropical seasonal forest A biome with warm temperatures and pronounced wet and dry seasons, dominated by deciduous trees that shed their leaves during the dry season.

Tundra The coldest biome, characterized by a treeless expanse above permanently frozen soil.

Type I functional response A functional response in which a predator’s rate of prey consumption increases in a linear fashion with an increase in prey density until satiation occurs.

Type II functional response A functional response in which a predator’s rate of prey consumption begins to slow down as prey density increases and then plateaus when satiation occurs.

Type III functional response A functional response in which a predator exhibits low prey consumption under low prey densities, rapid consumption under moderate prey densities, and slowing prey consumption under high prey densities.

Ultimate hypothesis A hypothesis that addresses why an organism responds in a certain way to its environment in terms of the fitness costs and benefits of the response.

Upwelling An upward movement of ocean water.

Variance of the mean A measurement that indicates the spread of the data around the mean of a population when every member of the population has been measured.

Vector An organism that a parasite uses to disperse from one host to another.

Vegetative reproduction A form of asexual reproduction in which an individual is produced from the nonsexual tissues of a parent.

Vertical transmission When a parasite is transmitted from a parent to its offspring.

Visible light Wavelengths in between infrared and ultraviolet radiation that are visible to the human eye.

Warning coloration A strategy in which distastefulness evolves in association with very conspicuous colors and patterns. Also known as Aposematism.

Water potential A measure of the water’s potential energy.

Watershed An area of land that drains into a single stream or river.

Weather The variation in temperature and precipitation over periods of hours or days.

Weathering The physical and chemical alteration of rock material near Earth’s surface.

Wilting point The water potential at which most plants can no longer retrieve water from the soil, which is about –1.5 MPa.

Woodland/shrubland A biome characterized by hot, dry summers and mild, wet winters, a combination that favors the growth of drought-tolerant grasses and shrubs.

Zero growth isocline See Equilibrium isocline.