BIO 170 Unit 5: Population Ecology and Ecosystems Flashcards
Pre-Lecture Vocabulary and Definitions for Population Ecology
Abiotic: Refers to the non-living physical and chemical elements in the ecosystem, such as sunlight, temperature, soil, and water.
Aphotic zone: The portion of a lake or ocean where there is little or no sunlight; it is formally defined as the depths beyond which less than of sunlight penetrates.
Benthic zone: The lowest ecological region of a body of water, including the sediment surface and some sub-surface layers.
Benthos: The community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream.
Biome: A large naturally occurring community of flora and fauna occupying a major habitat, e.g., forest or tundra.
Biosphere: The global sum of all ecosystems; the zone of life on Earth.
Biotic: Relating to or resulting from living things, especially in their ecological relations.
Carrying capacity (): The maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available.
Cohort: A group of individuals of the same age, from birth until all are dead.
Climate: The long-term prevailing weather conditions in a given area.
Climograph: A plot of the annual mean temperature and precipitation in a particular region.
Community: All the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction.
Coral reef: A diverse underwater ecosystem held together by calcium carbonate structures secreted by corals.
Deep-sea hydrothermal vent: A fissure on the seafloor from which geothermally heated water issues.
Demography: The study of the vital statistics of a population and how they change over time.
Density: The number of individuals per unit area or volume.
Density-dependent: Referring to any characteristic that varies with population density.
Density-independent: Referring to any characteristic that is not affected by population density.
Dispersal: The movement of individuals or gametes away from their area of origin or from centers of high population density.
Dispersion: The pattern of spacing among individuals within the boundaries of the population.
Disturbance: An event such as a storm, fire, or human activity that changes a community, removing organisms from it and altering resource availability.
Ecology: The scientific study of the interactions between organisms and the environment.
Ecosystem: The community of organisms in an area and the physical factors with which those organisms interact.
Emigration: The movement of individuals out of a population.
Eutrophic lake: A lake that has a high rate of biological productivity supported by a high rate of nutrient cycling.
Exponential population growth: Population increase under ideal conditions ().
Immigration: The inward movement of individuals into a population.
Intertidal zone: The area that is above water at low tide and under water at high tide.
Intrinsic rate of increase (): The per capita rate at which an exponentially growing population increases in size at each instant in time.
K-selection: Selection for life history traits that are sensitive to population density; also called density-dependent selection.
Landscape: A mosaic of connected ecosystems.
Life history: The traits that affect an organism's schedule of reproduction and survival.
Life table: An age-specific summary of the survival pattern of a population.
Limnetic zone: In a lake, the well-lit, open surface waters far from shore.
Littoral zone: In a lake, the shallow, well-lit waters close to shore.
Logistic population growth: Population growth that levels off as population size approaches carrying capacity ().
Marine benthic zone: The ocean floor.
Metapopulation: A group of spatially separated populations of one species that interact through immigration and emigration.
Oceanic pelagic zone: Most of the ocean's waters far from shore, constantly mixed by ocean currents.
Oligotrophic lake: A nutrient-poor, clear lake with few phytoplankton.
Pelagic zone: All the water of the ocean that is not close to the bottom or near the shore.
Photic zone: The upper layer of ocean or lake water in which photosynthesis is possible.
Population: A group of individuals of a single species living in the same general area.
r-selection: Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection.
Survivorship curve: A plot of the number of members of a cohort that are still alive at each age.
Territoriality: A behavior in which an animal defends a bounded physical space against encroachment by other individuals.
Thermocline: A narrow layer of abrupt temperature change in the ocean and in many temperate-zone lakes.
Chapter 40: Population Ecology and Distribution
Scope of Ecology: * Organismal Ecology: Includes subdisciplines of physiological, evolutionary, and behavioral ecology; focuses on how an organism's structure, physiology, and behavior meet environmental challenges. * Population Ecology: Focuses on factors affecting population size and why it changes through time. * Community Ecology: Examines how interactions between species, such as predation and competition, affect community structure and organization. * Ecosystem Ecology: Emphasizes energy flow and chemical cycling between organisms and the environment. * Landscape Ecology: Focuses on the factors controlling exchanges of energy, materials, and organisms across multiple ecosystems. * Global Ecology: Examines how the regional exchange of energy and materials influences the functioning and distribution of organisms across the entire biosphere.
Latitudinal Variation in Sunlight Intensity: * Earth's curved shape causes latitudinal variation in the intensity of sunlight. Sunlight strikes the tropics ( North and South latitude) most directly, providing more heat and light per unit of surface area. * At higher latitudes, sunlight strikes Earth at an oblique angle, and thus the light energy is more diffuse on Earth's surface.
Global Air Circulation and Precipitation Patterns: * Intense solar radiation at the equator initiates a global pattern of air circulation and precipitation. High temperatures in the tropics evaporate water and cause warm, wet air masses to rise and flow toward the poles. * As rising air masses cool, they release their water content, creating abundant precipitation in tropical regions. * High-altitude air masses, now dry, descend toward Earth at around North and South, absorbing moisture from the land and creating arid climates (deserts). * Air then flows toward the poles and the equator; at North and South, the air rises again and releases precipitation (though less than the tropics).
Seasonality (40.1): * Seasonality is caused by Earth's tilt on its axis () and its annual passage around the sun. * This tilt causes variation in day length, solar radiation, and temperature.
Effect of Bodies of Water on Climate: * Large bodies of water moderate the climate of nearby land due to the high specific heat of water. * During a hot day, when land is warmer than the water, air over the land heats up and rises, drawing a cool breeze from the water across the land. * Conversely, because water cools more slowly than land, at night or during winter, the air over the warmer water rises and draws cooler air from the land back over the water, replacing it with warmer air from offshore.
Effect of Mountains on Climate: * When warm, moist air approaches a mountain, the air rises and cools, releasing moisture on the windward side of the peak. * On the leeward side, cooler, dry air descends, absorbing moisture and producing a "rain shadow," which often creates desert conditions.
Major Terrestrial Biomes: * Tropical Forest: Constant high temperatures (); Tropical rain forests have constant rainfall, while tropical dry forests have seasonal rainfall. * Desert: Low precipitation (typically less than per year); temperature varies seasonally and daily (may be hot or cold). * Savanna: Seasonal rainfall; warm year-round; dominated by grasses and forbs. * Chaparral: Seasonal precipitation (rainy winters, dry summers); cool fall/winter/spring, hot summers. * Temperate Grassland: Highly seasonal precipitation; cold winters and hot summers. * Northern Coniferous Forest (Taiga): Largest terrestrial biome; periodic droughts; winters are cold, summers may be hot. * Temperate Broadleaf Forest: Significant precipitation in all seasons; winters average , summers up to ; distinct vertical layers. * Tundra: High winds and low temperatures; covers expansive areas of the Arctic; contains permafrost (permanently frozen layer of soil).
Chapter 40.2-40.6: Aquatic Biomes and Population Dynamics
Major Aquatic Biomes (40.2): * Lakes: Vary in size; stratified by light (photic/aphotic) and temperature; include oligotrophic (low nutrient/high oxygen) and eutrophic (high nutrient/low oxygen) types. * Wetlands: Inundated by water at least some of the time; support plants adapted to water-saturated soil. * Streams and Rivers: Characterized by flow; headwaters are cold/clear/turbid, while downstream is warmer and more turbid. * Estuaries: Transition area between river and sea; salinity varies spatially and temporally. * Intertidal Zones: Periodically submerged and exposed by the tides; oxygen and nutrient levels are high. * Oceanic Pelagic Zone: Vast realm of open blue water; oxygen levels are high, nutrient levels generally lower than coastal waters. * Coral Reefs: Formed from the calcium carbonate skeletons of corals; require high oxygen and solid substrate. * Marine Benthic Zone: Seafloor below surface waters; mostly soft sediments; organisms include invertebrates and fish.
Limits to Distribution (40.3): * Dispersal: Species may not be present in an area because they cannot reach it (geographic barriers) or have not had enough time. * Biotic Factors: Interactions with other species, such as predation, herbivory, competition, or the presence of parasites/pathogens. * Abiotic Factors: * Temperature: Affects biological processes; most organisms cannot maintain active metabolism at very high or low temperatures. * Water and Oxygen: Water availability affects desiccation risk; oxygen concentration can limit respiration in aquatic environments. * Salinity: Affects the water balance of organisms through osmosis. * Sunlight: Provides energy for photosynthesis; can limit the depth of aquatic plant growth. * Rocks and Soil: Physical structure, pH, and mineral composition limit the distribution of plants and the animals that feed on them.
Population Density and Dispersion (40.4): * Density Dynamics: Density is not static; it changes through birth and immigration (additions) and death and emigration (subtractions). * Patterns of Dispersion: 1. Clumped: Individuals aggregate in patches (most common; associated with resource availability or mating). 2. Uniform: Evenly spaced; often result of antagonistic social interactions like territoriality. 3. Random: Unpredictable spacing; occurs in the absence of strong attractions or repulsions. * Life Table: Summarizes age-specific survival; follows a cohort from birth to death to calculate the proportion surviving at each age. * Survivorship Curves: 1. Type I: Low death rates during early/middle life, followed by a steep increase among older age groups (e.g., humans). 2. Type II: Constant death rate over the organism's life span (e.g., some rodents). 3. Type III: Very high death rates for the young, followed by a lower death rate for those that survive to a certain age (e.g., many fish and marine invertebrates). * Reproductive Rate: Demographers look at females producing females; reproductive tables vary by age and provide data on the average number of female offspring produced by a female in a specific age group.
Population Growth (40.5): * Increase Factors: Births and Immigration. * Decrease Factors: Deaths and Emigration. * Exponential Growth: Growth under ideal conditions with unlimited resources; results in a J-shaped curve. * Logistic Growth: Incorporates the carrying capacity (); per capita rate of increase approaches zero as the population size nears ; results in an S-shaped (sigmoidal) curve.
Life History and Selection (40.6): * Life History: Comprised of three variables: when reproduction begins, how often the organism reproduces, and how many offspring are produced per reproductive episode. * Trade-offs: Organisms have finite resources; high investment in current reproduction often reduces the chance of survival or future reproduction (e.g., large number of small seeds vs. small number of large seeds). * K-selection (Density-Dependent): Selection for traits advantageous at high densities; competitive ability is high (e.g., elephants). * r-selection (Density-Independent): Selection for traits that maximize growth at low densities; high reproductive output (e.g., bacteria, weeds). * Density-Dependent Factors: Regulation mechanisms include competition for resources, territoriality, disease, predation, and toxic waste. * Metapopulation: A network of local populations linked by immigration and emigration.
Chapter 41: Species Interactions
Interspecific Interactions (41.1): * Competition (): Individuals of different species compete for a resource that limits growth and survival. * Predation (): One species (predator) kills and eats the other (prey). * Herbivory (): An organism eats parts of a plant or alga. * Parasitism (): One organism (parasite) derives nourishment from another (host), which is harmed in the process. * Mutualism (): Both species benefit from the interaction. * Commensalism (): One species benefits while the other is neither helped nor harmed.
Ecological Niche: The sum of a species' use of the biotic and abiotic resources in its environment (its "profession").
Niche Distinction: * Fundamental Niche: The niche potentially occupied by a species. * Realized Niche: The portion of the fundamental niche the species actually occupies, regulated by competition or predation.
Character Displacement: The tendency for characteristics to be more divergent in sympatric populations (living together) than in allopatric populations (living apart). It is more likely when species are competing for similar resources.
Defensive Adaptations: * Cryptic Coloration: Camouflage that makes prey difficult to see. * Aposematic Coloration: Bright warning coloration, typically associated with chemical defenses (e.g., poison dart frogs). * Batesian Mimicry: A harmless species mimics a harmful or unpalatable one.
Parasites: * Endoparasites: Live within the body of the host (e.g., tapeworms). * Ectoparasites: Feed on the external surface of the host (e.g., ticks, lice).
Community Diversity (41.2): * Components: Species richness (number of different species) and relative abundance (proportion of each species in the community). * Stability: Diverse communities are more productive, better able to withstand environmental stress, and more resistant to invasive species. * Trophic Structure: The feeding relationships between organisms; organized into a hierarchy: primary producers -> primary consumers -> secondary consumers -> tertiary consumers -> quaternary consumers.
Species with Large Impact: * Foundation Species: Have strong effects due to their high biomass or large size (e.g., trees in a forest). * Keystone Species: Exert strong control on a community by their ecological roles (not necessarily abundant; e.g., sea stars). * Ecosystem Engineers: Species that dramatically alter their environment (e.g., beavers).
Bottom-Up vs. Top-Down Controls: * Bottom-Up: Presence or absence of mineral nutrients controls plant numbers, which control herbivore numbers, which control predator numbers (). * Top-Down: Predation mainly controls community organization; predators limit herbivores, which in turn limit plants ().
Disturbance and Succession (41.3): * Intermediate Disturbance Hypothesis: States that moderate levels of disturbance foster greater species diversity than either high or low levels of disturbance. * Ecological Succession: The sequence of community and ecosystem changes after a disturbance. * Primary Succession: Occurs in a lifeless area where no soil exists (e.g., volcanic island). * Secondary Succession: Occurs where an existing community has been cleared by a disturbance that leaves the soil intact (e.g., forest fire).
Biogeographic Factors (41.4): * Latitudinal Gradients: Species richness is generally highest in the tropics and declines toward the poles due to evolutionary history (longer growing season) and climate (high solar input and water). * Area Effects: The species-area curve states that, all other factors being equal, a larger geographic area has more species.
Pathogens (41.5): Pathogens (viruses, bacteria, protists) can significantly alter community structure by reducing the population of key species (e.g., sudden oak death).
Chapter 42: Ecosystems and Energy
Conservation Laws (42.1): * Conservation of Energy: Energy enters an ecosystem as solar radiation, is conserved, and leaves as heat. Energy cannot be recycled; it must be continuously supplied. * Conservation of Mass: Chemical elements (like carbon/nitrogen) are continually recycled within ecosystems; unlike energy, matter is NOT lost but changes form.
Energy Flow and Nutrient Cycling: Energy flows through ecosystems (unidirectional), while chemicals/nutrients cycle within them.
Primary Production (42.2): * Gross Primary Production (GPP): The total primary production in an ecosystem; the amount of energy from light converted to chemical energy per unit time. * Net Primary Production (NPP): Equal to GPP minus the energy used by primary producers for autotrophic respiration (); represents the storage of chemical energy available to consumers (). * Net Ecosystem Production (NEP): Measure of the total biomass accumulation during a given period; ( is total respiration of all organisms).
Limits to Primary Production: * Aquatic: Light (depth) and Nutrients (nitrogen and phosphorus are often limiting). Eutrophication is the rapid growth of algae due to excess nutrients, leading to oxygen depletion. * Terrestrial: Temperature and Moisture. Nitrogen and phosphorus are also common limiting nutrients in soils.
Trophic Efficiency (42.3): * The percentage of production transferred from one trophic level to the next; typically only . * Pyramids: Pyramids of energy always show a sharp decrease with higher levels. Pyramids of biomass usually narrow at the top, but can be inverted in certain aquatic systems (where phytoplankton reproduce fast but have low standing crop).
Biogeochemical Cycles (42.4): * Water Cycle: Driven by solar energy (evaporation, condensation, precipitation). * Carbon Cycle: Balance between photosynthesis (removes ) and respiration (adds ); burning fossil fuels and wood adds excess . * Nitrogen Cycle: Involves nitrogen fixation (converting to forms plants can use) by bacteria; crucial for proteins and nucleic acids. * Phosphorus Cycle: Primarily localized in rocks/sediments; weathering adds phosphate to soil; crucial for ATP and DNA.
Restoration Ecology (42.5): * Goal: To initiate or speed up the recovery of degraded ecosystems. * Bioremediation: The use of organisms (prokaryotes, fungi, plants) to detoxify polluted ecosystems. * Biological Augmentation: Uses organisms to add essential materials to a degraded ecosystem (e.g., nitrogen-fixing plants).
Chapter 43: Global Ecology and Conservation Biology
Three Levels of Biodiversity (43.1): 1. Genetic Diversity: Genetic variation within a population and between populations. 2. Species Diversity: The variety of species in an ecosystem or across the biosphere. 3. Ecosystem Diversity: The variety of the biosphere's ecosystems.
Threatened vs. Endangered: * Endangered: A species that is in danger of extinction throughout all or a significant portion of its range. * Threatened: A species that is considered likely to become endangered in the foreseeable future.
Biodiversity Benefits: Provides food, medicine (e.g., Rosy Periwinkle for leukemia), and ecosystem services (water purification, pollination, waste decomposition).
Human Threats: * Habitat Loss: The single greatest threat to biodiversity. * Introduced Species: Non-native species that disrupt their new community. * Overharvesting: Harvesting wild organisms at rates exceeding their ability to rebound. * Global Change: Alterations in climate, atmospheric chemistry, and ecological systems (e.g., acid rain).
Conservation Approaches (43.2): * Extinction Vortex: A downward population spiral in which inbreeding and genetic drift combine to cause a small population to shrink and, unless the trend is reversed, become extinct. * Minimum Viable Population (MVP): The minimum population size at which a species can sustain its numbers. * Effective Population Size (): The estimate of the size of a population based on the numbers of females and males that successfully breed; calculated as .
Landscape and Regional Conservation (43.3): * Boundaries/Edges: Transition zones between ecosystems; some species thrive here, but edge effects can decrease interior habitat quality. * Movement Corridors: Narrow strips or clumps of habitat connecting isolated patches; promote dispersal and reduce inbreeding. * Hotspots: Small areas with numerous endemic species (found nowhere else) and many endangered species.
Human Impacts on the Environment (43.4): * Nutrient Enrichment: Human activity (fertilizers) often removes nutrients from one area and adds them to another, leading to a critical load (the amount of added nutrient that can be absorbed without damaging ecosystem integrity). * Biological Magnification: Toxins become more concentrated in successive trophic levels of a food web. * Plastics: Microplastics (particles less than ) and larger plastics persist in the environment, leaching toxins and harming wildlife. * Climate Change: Caused by the greenhouse effect where greenhouse gases (like and methane) trap heat. Consequences include rising sea levels, loss of habitat, and shifting geographic ranges.
Human Population (43.5): The human population is no longer growing exponentially but is still increasing; current estimates suggest it will stabilize between and billion by 2050.
Sustainable Development (43.6): Development that meets the needs of people today without limiting the ability of future generations to meet their needs.