eco q&a
•
Abiotic: Non-living factors in the environment1.
•
Abundance: The total number of individuals within a defined population2....
•
Adaptation: A trait that enhances survival and reproduction of an organism in its environment1....
•
Adhesion-adapted: A seed dispersal strategy6....
•
Age distribution: The proportion of individuals in a population belonging to different age groups3....
•
Allele: A variant form of a gene1.
•
Allele frequencies: The proportion of different alleles in a population1.
•
Allozyme: Variant forms of an enzyme that are produced by different alleles at a single locus6.
•
Aril: A seed dispersal strategy involving vertebrate consumption6....
•
Artificial selection: The process by which humans consciously select for or against particular features in organisms1.
•
Birthrate: The number of offspring produced per female within a given time interval3....
•
Biosphere: The regions of the surface, atmosphere, and hydrosphere of the earth occupied by living organisms1....
•
Biotic: Living factors in the environment1.
•
Carrying capacity (K): The maximum population size of a species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment15.
•
Citizen scientist: A volunteer who collects and analyzes data relating to the natural world, typically as part of a collaborative project with professional scientists5.
•
Climbers: Climbing plants and vines12.
•
Clumped distribution: A distribution pattern where individuals in a population are clustered together in groups2....
•
Clutch size: The number of eggs produced by a female during a single reproductive event3....
•
Cohort: A group of individuals in a population born during the same time interval (often within a single year)3....
•
Cohort life table: A life table that tracks a single cohort of individuals from birth until the last one dies10....
•
Colonization cycle: The interplay between upstream and downstream dispersal, particularly in stream ecosystems4....
•
Community: An assemblage of populations of different species that live and interact in the same area5....
•
Competitive plant: A plant strategy that is adapted to low disturbance and low stress conditions6....
•
Conceptual models: Terms or ideas in pictures or diagrams5....
•
Density: The number of individuals per unit area or volume within a defined population2....
•
Density-dependent factor: A factor that affects population size or growth depending on the population density15.
•
Density-independent factor: A factor that affects population size or growth regardless of the population density15.
•
Directional selection: A form of natural selection that favors one extreme phenotype, causing a shift in the population’s mean phenotype over time1....
•
Dispersal: The movement of individuals away from their birth site or existing populations4....
•
Disruptive selection: A form of natural selection that favors both extreme phenotypes and selects against intermediate ones1....
•
Distribution: The size, shape, and location of the area a population occupies2....
•
Drift: Refers to the random fluctuations in allele frequencies within a population (see Genetic Drift)10.
•
Ecology: Study of relationships between organisms and the environment5....
•
Ecosystem: A community of living organisms (biotic) in conjunction with the nonliving components of their environment (abiotic), interacting as a system5....
•
Elaiosome: A structure on some seeds that attracts ants, which then disperse the seeds6....
•
Endemic: A species that is found exclusively in a particular geographic area2....
•
Epiphyte: A plant that grows on another plant but is not parasitic, such as many orchids and bromeliads that grow on tropical trees5....
•
Evolution: Change in the heritable characteristics of biological populations over successive generations5....
•
Ex situ: Refers to conservation methods involving the removal of organisms from their original habitat (e.g., zoos, seed banks)5.
•
Experiments: A scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact5....
•
Exponential population growth: Population increase under idealized conditions15.
•
Fecundity: The number of offspring produced by an organism6....
•
Fecundity schedule: A table showing the average number of offspring produced by females of different ages in a population10....
•
Forb: A herbaceous, non-graminoid plant6....
•
Founder effect: A form of genetic drift that occurs when a new population is established by a small subset of the original population7....
•
Fundamental niche: The full range of environmental conditions in which a species could live and reproduce2....
•
Generation time (T): The average age of parents in a population8....
•
Genetic drift: Random changes in gene frequencies within a population, particularly significant in small populations1....
•
Geometric population growth: Population increase described with discrete time intervals15.
•
Geometric rate of increase (λ): The finite rate of population change over a given time interval (usually a year), often applied to populations with discrete breeding seasons8....
•
Germination: The process by which a plant emerges from a seed or spore and begins to grow6.
•
Gonadosomatic index (GSI): The ratio of gonad weight to body weight, used as a measure of reproductive effort6....
•
Graminoid: Grass and grass-like plants6....
•
Growth form: The characteristic structure and life cycle of a plant, such as tree, shrub, or herb6....
•
Hardy-Weinberg principle: A principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors1.
•
Heritability: The proportion of total phenotypic variation attributable to genetic variation1....
•
In situ: Refers to conservation methods conducted within the natural habitat of an organism5.
•
Inbreeding: The mating of individuals or organisms that are closely related through common ancestry1....
•
Intrinsic rate of increase: The rate at which a population increases in size if there are no density-dependent forces regulating the population15.
•
Iteroparity: A life history strategy in which organisms reproduce multiple times throughout their life6.
•
K selection: Refers to the carrying capacity in the logistic growth equation and is envisioned as a form of natural selection favoring more efficient utilization of resources, such as food and nutrients6....
•
Life expectancy (ex): The average number of time intervals a member of a given age is expected to live beyond its present age51.
•
Life history: The adaptations of an organism that influence aspects of its biology, such as the number of offspring it produces, its survival, and its size and age at reproductive maturity6....
•
Life table: A summary of the age-specific survival and reproductive rates of individuals in a population8....
•
Loci: The plural form of locus, referring to multiple locations on a chromosome6.
•
Locus: The specific location or position of a gene, DNA sequence, or position on a chromosome1.
•
Logistic equation: Mathematical equation that describes the S-shaped curve of logistic population growth15.
•
Logistic population growth: A pattern of population growth in which the population size increases rapidly at first, but then slows down as the population becomes more crowded15.
•
Large-scale phenomena: Ecological processes and patterns occurring over broad areas where substantial environmental change is present2....
•
Metapopulation: A population consisting of several subpopulations living in spatially separated patches linked by dispersal8....
•
Microsatellite DNA: Regions of DNA comprised of short, repeating sequences that are used for genetic markers1.
•
Modeling: The process of producing a simplified representation of a real-world system or phenomenon5....
•
Natural experiment: An observational study in which an event or situation that allows for the random or seemingly random assignment of study subjects to different groups is exploited to answer a particular question5....
•
Natural selection: Differential survival and reproduction among phenotypes1....
•
Net reproductive rate (R0): The average number of offspring a female produces in her lifetime, adjusted for survival7....
•
Niche: Summarizes environmental factors that influence growth, survival, and reproduction of a species2....
•
Numerical response: A change in predator population size as a response to a change in prey density10....
•
Observation: The active acquisition of information from a primary source5....
•
Opportunistic: Shares some features with r selected and ruderal species72.
•
Patchy population: Metapopulations where dispersal between patches or populations is high7....
•
Per capita rate of increase (r): The intrinsic rate of increase of a population, representing the rate of population change per individual over a given time8....
•
Phenotype: The observable characteristics of an organism, which are the result of gene-environment interactions1....
•
Phenotypic plasticity: The capacity of an organism to alter its phenotype in response to changes in its environment1.
•
Pheromone: A chemical substance produced and released into the environment by an animal, especially a mammal or an insect, affecting the behavior or physiology of others of its species2....
•
Phenology: The study of periodic events in biological life cycles and how these are influenced by environmental variations, especially seasonal changes in temperature and rainfall6.
•
Polygenic traits: Traits that are controlled by multiple genes1.
•
Population: A group of individuals of a single species inhabiting a specific area1....
•
Population bottleneck: A form of genetic drift that occurs when a large portion of a population is randomly killed7....
•
Population dynamics: Concerned with factors influencing expansion, decline, and maintenance of populations10....
•
Population genetics: The study of genetic variation within populations, and how this variation changes over time1....
•
Quantitative genetics: The study of continuously measured traits and their underlying genetic basis1.
•
Quantitative Models: Mathematical and use equations to understand and predict relationships5....
•
r selection: Refers to the per capita rate of increase, r, and is thought to favor higher population growth rate6....
•
Random distribution: A distribution pattern where individuals are spaced independently of each other2....
•
Realized niche: The restricted set of environmental conditions where a species actually lives, due to interactions with other species2....
•
Regular distribution: A distribution pattern where individuals in a population are evenly spaced2....
•
Reproductive effort: The proportion of its resources an organism expends on reproduction6....
•
Ruderal: A plant strategy adapted to high disturbance and low stress conditions25....
•
Scatterhoarded: Seeds gathered and stored in caches6....
•
Semelparity: A life history strategy in which organisms reproduce only once in their life6.
•
Sigmoidal population growth curve: S-shaped curve illustrating logistic growth, where population size stabilizes at carrying capacity15.
•
Small-scale phenomena: Ecological processes and patterns occurring within a limited or localized area2.
•
Stable age distribution: A population in which the proportion of individuals in each age class remains constant over time10....
•
Stabilizing selection: A form of natural selection that favors intermediate phenotypes1....
•
Static life table: A life table based on data collected at a single point in time9....
•
Stress: Environmental conditions that limit plant growth or survival6.
•
Stress-tolerant plant: A plant strategy adapted to low disturbance and high stress conditions6....
•
Subpopulation: A smaller group of individuals within a larger metapopulation8....
•
Survivorship curve: A graph showing the pattern of survival in a population, where the x-axis shows the age and the y-axis shows the probability of survival7....
•
Type I survivorship curve: A survivorship curve characterized by high survival throughout life until old age7....
•
Type II survivorship curve: A survivorship curve characterized by a constant mortality rate throughout the lifespan7....
•
Type III survivorship curve: A survivorship curve characterized by high mortality early in life, with low mortality for individuals who survive to older ages7....
•
Urban ecology: The study of the interactions of organisms and their environment within an urban context, including how urbanization affects biodiversity, habitat fragmentation, and ecosystem services.
What does the equation 1t tN N B I D E-= + + - - represent in population dynamics?
How can dispersal affect local population densities, and provide one real-world example?
What are the key differences between the three types of survivorship curves (Type I, II, III)?
Explain how the principle of allocation leads to a trade-off between the number and size of offspring.
How does genetic drift differ from natural selection in its effect on gene frequencies?
What factors determine the geographic range of a species?
Distinguish between a population's distribution and its abundance.
What are the differences between the geometric rate of increase (λ), net reproductive rate (R0) and per capita rate of increase (r) and under what conditions are they the same?
Describe how stable photosymbiosis is established and maintained by some sea slugs of the Cladobranchia.
How do r selected and K selected species differ, and in what type of environment is each favored?
Quiz Answer Key
The equation 1t tN N B I D E-= + + - - describes population change over time, where Nt is the population size at time t, B is the number of births, I is the number of immigrants, D is the number of deaths, and E is the number of emigrants during a specific time interval. It's a fundamental expression of the processes that influence population size.
Dispersal can increase local population densities through immigration, which brings new individuals into an area. Conversely, emigration decreases local densities as individuals leave. For instance, Africanized honeybees in the Americas have increased local densities in new areas through dispersal.
Type I curves show high survivorship early and middle life, followed by a sharp decline in old age. Type II curves exhibit a constant mortality rate throughout life. Type III curves display high mortality early in life, with few individuals surviving to older ages.
The principle of allocation means that an organism's energy resources are limited. If an organism invests a lot of energy in producing many offspring, it has less energy for each individual offspring, leading to smaller sizes. The opposite is also true.
Genetic drift is a random process that alters gene frequencies due to chance events, especially in small populations. Natural selection is a non-random process where differential survival and reproduction of individuals based on heritable traits leads to changes in gene frequencies.
The geographic range of a species is determined by a variety of factors, including climate, food availability, habitat suitability, and the presence of competitors or predators. Abiotic factors such as temperature and moisture can also indirectly limit distributions through effects on food, water, and habitat.
A population's distribution describes the spatial arrangement or location of individuals of a species within an area, including the size and shape of their range. Abundance refers to the total number of individuals within that population, describing the quantity rather than location of individuals.
The geometric rate of increase (λ) is the finite rate of population change over a given time interval. The net reproductive rate (R0) is the number of offspring produced by a female over her lifetime. The per capita rate of increase (r) is the instantaneous rate of population growth per individual. If a species breeds once a year and lives only one year, then R0 = λ, otherwise they are different, and r is usually derived from R0 and generation time (T).
Some sea slugs within the Cladobranchia establish stable photosymbiosis by obtaining photobionts from their cnidarian prey or the water column. These photobionts are stored in the digestive gland system where they continue to photosynthesize, providing the slug with nutrition. The mechanisms of recognition, uptake, and maintenance are not well understood.
r-selected species favor higher rates of population growth and are typically found in disturbed habitats. K-selected species favor more efficient utilization of resources and are found in stable environments. In r-selected environments, disturbance keeps densities low, whereas in K-selected environments, populations often reach carrying capacity.
Essay Questions
Using examples from the provided texts, discuss how both abiotic and biotic factors interact to limit the geographic distribution of species.
Explain how life table data can be used to calculate net reproductive rate (R0), generation time (T), and the per capita rate of increase (r) and how these values can help predict population growth or decline, referencing real species data in the text.
Discuss the various types of selection (stabilizing, directional, and disruptive) using examples from the provided materials, with special emphasis on heritability.
Analyze the differences between stable and unstable photosymbiosis within the Cladobranchia, including the mechanisms of photobiont acquisition and the potential benefits for the sea slugs.
Compare and contrast the concepts of r-selection and K-selection and discuss how these life history strategies are associated with different environmental conditions and with the "ruderal, competitive, and stress-tolerant" strategies of plant life histories.
Glossary of Key Terms
Abundance: The total number of individuals within a defined population.
Age Distribution: The proportion of individuals in a population belonging to different age groups.
Birthrate: The number of offspring produced per female within a given time interval.
Clumped Distribution: A distribution pattern where individuals in a population are clustered together in groups.
Cohort: A group of individuals in a population born during the same time interval (often within a single year).
Colonization Cycle: The interplay between downstream and upstream dispersal, especially in stream organisms, contributing to population dynamics.
Density: The number of individuals per unit area or volume.
Directional Selection: A type of natural selection that favors one extreme phenotype, causing a shift in the population's traits.
Dispersal: The movement of individuals from their birth site to other locations.
Disruptive Selection: A form of natural selection that favors both extreme phenotypes and selects against intermediate ones.
Distribution: The size, shape, and location of the area a population occupies.
Endemic: A species that is found exclusively in a particular geographic area.
Fecundity Schedule: A table showing the average number of offspring produced by females of different ages in a population.
Founder Effect: A form of genetic drift that occurs when a new population is established by a small subset of the original population.
Fundamental Niche: The total range of environmental conditions under which a species could survive and reproduce.
Generation Time (T): The average age of parents in a population, also the average time between the birth of a parent and the birth of its offspring.
Geometric Rate of Increase (λ): The finite rate of population change over a given time interval.
Genetic Drift: Random changes in gene frequencies in a population due to chance events.
Life Table: A table summarizing the survival and reproduction rates of a cohort in a population.
Metapopulation: A group of spatially separated subpopulations of the same species that interact through dispersal.
Net Reproductive Rate (R0): The average number of offspring produced by a female during her lifetime.
Niche: The ecological role and requirements of a species, including all factors that influence its growth, survival, and reproduction.
Numerical Response: A change in predator population size as a response to a change in prey density.
Patchy Population: Metapopulations where dispersal between patches or populations is high.
Per Capita Rate of Increase (r): The intrinsic rate of increase of a population, representing the rate of population change per individual over a given time.
Phenotype: Observable characteristics of an organism, resulting from the interaction of its genotype and environment.
Pheromone: A chemical substance produced and released into the environment by an animal, especially a mammal or an insect, affecting the behavior or physiology of others of its species.
Population: A group of individuals of the same species inhabiting a specific area.
Population Bottleneck: A sharp reduction in the size of a population due to a random event, which can alter gene frequencies.
Principle of Allocation: The concept that organisms have limited energy resources, leading to trade-offs between different functions.
Random Distribution: A distribution pattern where individuals in a population are spaced unpredictably.
Realized Niche: The actual range of environmental conditions under which a species lives, often due to interactions with other species.
Regular Distribution: A distribution pattern where individuals in a population are spaced uniformly.
r -selection: A life history strategy that prioritizes high reproductive rates in disturbed or unstable environments.
K -selection: A life history strategy that prioritizes efficient resource use in stable environments, often near carrying capacity.
Small-scale phenomena: Ecological phenomena that occur over areas with little environmental change.
Stable Age Distribution: A population where the proportions of individuals in each age class remain constant over time.
Stabilizing Selection: A form of natural selection that favors intermediate phenotypes and selects against extreme ones.
Static Life Table: A life table that summarizes survival and reproduction of all individuals alive during a certain time interval.
Subpopulation: A group of individuals within a population that are spatially separated but still have some interaction with other subpopulations.
Survivorship Curve: A graph showing the pattern of survival within a population over time.
Type I Survivorship Curve: A survivorship curve characterized by high survival rates early in life, followed by a sharp decrease in older age groups.
Type II Survivorship Curve: A survivorship curve characterized by a constant mortality rate throughout life.
Type III Survivorship Curve: A survivorship curve characterized by high mortality rates in early life, with relatively few individuals surviving to older age groups.