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Ecology, Density dependent, Chapter 54.1:Community interactions are…

- - - - The population will increase in size with every birth and with the immigration of individuals from other populations, and it will decrease in size with every death and with the emigration of individuals out of the population
        
        N=(B+I)-(D+E)
      - exponential population growth
        
        a population that experiences such ideal conditions increases in size by a constant proportion at each instant in time
        
        N represents population size and t represents time
        
        intrinsic rate of increase (r)
        
        the per capita rate at which an exponentially growing population increases in size at each instant in time
        
        J-shaped curve of exponential growth
        
        characteristic of some populations that are introduced into a new environment or whose numbers have been drastically reduced by a catastrophic event and are rebounding
  - - - a group of individuals of a single species living in the same general area
        
        described by their boundaries and size
      - Members of a population rely on the same resources, are influenced by similar environmental factors, and are likely to interact and breed with one another
      - density
        
        the number of individuals per unit area or volume
        
        mark-recapture method
        
        used estimate the size of wildlife populations
        
        x/n = s/N
        
        Immigration
        
        the influx of new individuals from other areas
        
        emigration
        
        the movement of individuals out of a population and into other locations
      - dispersion
        
        the pattern of spacing among individuals within the boundaries of the population
        
        3 Types of dispersion
        
        Clumping
        
        individuals are aggregated in patches
        
        Plants and fungi are often clumped; may also occur in animals due to different mating behaviors
        
        Humans
        
        uniform
        
        evenly spaced, pattern of dispersion may result from direct interactions between individuals in the population
        
        Animals exhibit this behavior as a result of antagonistic social interactions (territorial)
        
        Penguin
        
        Random
        
        Individuals are placed in random patterns, some may clump, some may be spread out
        
        Dandelions; usually occurs in organisms whose embryos carried by wind/in ocean water
      - Demographics
        
        the study of these vital statistics of populations and how they change over time
        
        The biotic and abiotic factors that influence population density and dispersion patterns also influence other characteristics of populations, including birth, death, and migration rates
        
        life table
        
        summarizes the survival and reproductive rates of individuals in specific age-groups within a population
        
        cohort
        
        a group of individuals of the same age, from birth until all of the individuals are dead
      - Survivorship Curves
        
        a plot of the proportion or numbers in a cohort still alive at each age
        
        Type I curve
        
        flat at the start, reflecting low death rates during early and middle life, and then drops steeply as death rates increase among older age-groups
        
        Humans and elephants
        
        Type II curve
        
        intermediate, with a constant death rate over the organism’s life span
        
        many invertebrates, lizards, and annual plants
        
        Type III curve
        
        curve drops sharply at the start, reflecting very high death rates for the young, but flattens out as death rates decline for those few individuals that survive the early period of die-off
        
        many fishes, and most marine invertebrates
  - - - K
      - The maximum population size that a particular environment can sustain
        
        Varies over space, time, and resources
        
        Energy, shelter, refuge from predators, nutrient availability, water, and sustainable nesting sites can all be limiting resources
    - - the per capita rate of population growth approaches zero as the population size nears the carrying capacity
        
        Some of the assumptions built into the logistic model clearly do not apply to all populations
        
        important for predicting how rapidly a particular population might increase in numbers after it has been reduced to a small size
      - (K-N)/K
        
        provides a useful starting point for thinking about how populations grow and for constructing more complex models
        
        use the model to estimate the critical size below which populations of certain organisms, such as the northern subspecies of the white rhinoceros
  - - - traits of an organism are evolutionary outcomes reflected in its development, physiology, and behavior
      - three key components
        
        when reproduction begins
        
        how often the organism reproduces
        
        how many offspring are produced per reproductive episode
      - semelparity
        
        one-shot” pattern of big-bang reproduction
        
        coho salmon
      - iteroparity
        
        repeated reproduction
        
        female loggerhead turtle
      - Trade-Offs
        
        There is a trade-off between offspring number and the amount of resources a parent can devote to each offspring
        
        occur because organisms do not have access to unlimited amounts of resources
        
        Plants and animals whose young have a low change of survival often produce many small offspring
        
        K-selection
        
        election for traits that are advantageous at high densities
        
        said to operate in populations living at a density near the limit imposed by their resources (the carrying capacity, K)
        
        Mature trees growing in an old-growth forest
        
        represent two extremes in a range of actual life histories
        
        r-selection
        
        selection for traits that maximize reproductive success in uncrowded environments
        
        said to maximize r, the intrinsic rate of increase, and occurs in environments in which population densities are well below carrying capacity or individuals face little competition
        
        Weeds growing in an abandoned agricultural field
  - - - density independent
        
        Any characteristics not affected by population density
        
        A birth rate or death rate that does not change with population density
        
        cannot consistently cause a population to decrease in size when it is large or increase in size when it is small
        
        temperature and precipitation can cause dramatic changes in population size
    - - influenced by many factors and in turn affect other species
      - boom-and-bust cycles
      - metapopulation
        
        A group of specifically separated populations of one species that interact through immigration and emigration
        
        can be thought of as occupying discrete patches of suitable habitat in a sea of otherwise unsuitable habitat.
  - - - The human population has grown explosively over the last four centuries
      - demographic transition
        
        The movement from high birth and death rates toward low birth and death rates
        
        accompany industrialization and improved living conditions
        
        associated with an increase in the quality of health care and sanitation as well as improved access to education
      - age structure
        
        the relative number of individuals of each age in the population
      - Carrying Capacity
        
        population ecologists project a global population of approximately 8.1–10.6 billion people in 2050
        
        difficult to estimate, and scientists use different methods to produce their estimates
        
        1.7 gha
      - Ecological Footprint
        
        summarizes the aggregate land and water area required by each person, city, or nation to produce all the resources it consumes and to absorb all the waste it generates
- - - - the variety of different kinds of organisms that make up the community
        
        2 components
        
        species richness
        
        the number of different species in the community
        
        relative abundance
        
        the proportion each species represents of all individuals in the community
      - Higher-diversity communities are often more resistant to invasive species
        
        invasive species
        
        organisms that become established outside their native range
      - trophic structure
        
        the structure and dynamics of a community also depend on the feeding relationships between organisms
        
        Trophic level
        
        The position an organism occupies in a food chain
        
        food chain
        
        The transfer of food energy upward from its source in plants and other autotrophs (primary producers) through herbivores (primary consumers) to carnivores (secondary, tertiary, and quaternary consumers) and eventually to decomposers
        
        energetic hypothesis
        
        suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain (10%)
        
        Food web
        
        a group of food chains are linked together
    - - (the total mass of all organisms in a habitat) than the single species plots each year.
      - Keystone species
        
        not usually abundant in a community
      - ecosystem engineers
        
        Species that dramatically alter their environment
    - - Top down Control
        
        Predation mainly controls community organization because predators limit herbivores, herbivores limit plants, and plants limit nutrient levels through nutrient uptake
        
        N<V<H<P
      - postulates a unidirectional influence from lower to higher trophic levels
        
        V > H
  - - - an event, such as a storm, fire, flood, drought, or human activity, that changes a community by removing organisms from it or altering resource availability
      - nonequilibrium model
        
        describes most communities as constantly changing after disturbance
    - - intermediate disturbance hypothesis
        
        moderate levels of disturbance foster greater species diversity than do high or low levels of disturbance.
        
        Humane Distrubance
        
        Agricultural development
        
        clear-cutting
        
        cattle grazing
      - High levels of disturbance reduce diversity by creating environmental stresses that exceed the tolerances of many species
        
        low levels of disturbance can reduce species diversity by allowing competitively dominant species to exclude less competitive ones
    - - The disturbed area may be colonized by a variety of species, which are gradually replaced by other species, which are in turn replaced by still other species
    - - begins in a virtually lifeless area where soil has not yet formed, such as on a new volcanic island or on the rubble (moraine) left by a retreating glacier
        
        secondary succession
        
        occurs when an existing community has been cleared by a disturbance that leaves the soil intact
        
        Yellowstone following the 1988 fires
  - - - Charles Darwin and Alfred Wallace found that plant and animal life was generally more abundant and diverse in the tropics than in other parts of the globe
      - Two key factors that can affect latitudinal gradients of species richness
        
        Evolutionary History
        
        Climate
        
        evapotranspiration
        
        the evaporation of water from soil and plants
        
        a function of solar radiation, temperature, and water availability
        
        much higher in hot areas with abundant rainfall than in areas with low temperatures or low precipitation
      - species-area curve
        
        All other factors being equal, the larger the geographic area of a community, the more species it has
        
        S=cA^z
    - - islands provide excellent opportunities for studying the biogeographic factors that affect the species diversity of communities
        
        immigration rate decreases as the number of species on the island gets larger
        
        extinction rate increases
  - - - disease-causing microorganisms, viruses, viroids, or prions
        
        produce especially clear effects when they are introduced into new habitats, as in the case of the fungus that causes chestnut blight
        
        White-band disease, caused by an unknown pathogen, has resulted in dramatic changes in the structure and composition of Caribbean reefs
        
        influence community structure in terrestrial ecosystems (SOD)
      - zoonotic pathogens
        
        transferred to humans from other animals, either through direct contact with an infected animal or by means of an intermediate species, called a vector
        
        vector
        
        An organism that transmits pathogens from one hose to another
        
        The vectors that spread zoonotic diseases are often parasites, including ticks, lice, and mosquitoes.
        
        Lyme disease
        
        avian flu
        
        Human activities are transporting pathogens around the world at unprecedented rates
        
        P. ramorum
    - - The programs that quarantine domestic birds or monitor their transport may be ineffective if avian flu spreads naturally through the movements of wild birds
- - - - one species, the predator, kills and eats the other, the prey
        
        ion attacking and eating an antelope
      - aposematic coloration
        
        Cryptic coloration
        
        camouflage, makes prey difficult to see
        
        warning coloration, such as that of poison dart frogs
      - Batesian mimicry
        
        a palatable or harmless species mimics an unpalatable or harmful species to which it is not closely related
      - Müllerian mimicry
        
        the more unpalatable prey there are, the faster predators learn to avoid prey with that particular appearance
    - - interspecific interaction that benefits both species
    - - commensalism (+/0)
        
        interaction between species that benefits one of the species but neither harms nor helps the other
    - - occurs when individuals of different species compete for a resource that limits the survival and reproduction of each species
      - Lynx and foxes
      - Competitive Exclusion
        
        2 similar species compete for the same limited resources, one will have a reproductive advantage and the other will be eliminated
    - - an herbivore eats parts of a plant or alga, thereby harming it
    - - the parasite, derives its nourishment from another organism, its host, which is harmed in the process
      - Endoparasites: feed externally
        
        Ectoparasites: feed internally
  - - - Ecologists can identify the fundamental niche of a species by testing the range of conditions in which it grows and reproduces in the absence of competitors
      - Species can partition their niches not just in space, as lizards and barnacles do, but in time as well
  - - - include predation, herbivory, and parasitism