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General Biology: Population, Community, Ecosystems, and Evolution

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  • Population

    A group of individuals of the same species living in the same geographic area.

  • Population density

    Number of individuals per unit area or volume.

  • Population distribution (dispersion) patterns

    Three types: Clumped (groups, most common), Uniform (evenly spaced), Random (unpredictable).

  • Birth Rate (Natality)

    Number of individuals produced per unit time.

  • Death Rate (Mortality)

    Number of individuals dying per unit time.

  • Population Growth Equation (Exponential Growth)

    \(G = rN\), where G = individuals added, r = per capita growth rate, N = population size; produces a J-shaped curve.

  • Carrying Capacity (K)

    The maximum population size an environment can support; produces a logistic (S-shaped) growth curve.

  • Density-Dependent Factors

    Factors whose effects increase as population density increases, e.g., disease, predation, competition, parasitism.

  • Density-Independent Factors

    Factors affecting populations regardless of size, e.g., frost, fires, floods, hurricanes, droughts.

  • Type I Survivorship Curve

    Low juvenile mortality, high mortality late in life; examples: humans, elephants.

  • Type II Survivorship Curve

    Equal chance of dying at any age; example: songbirds.

  • Type III Survivorship Curve

    Very high juvenile mortality, few survive to adulthood; examples: insects, many plants.

  • r-Selected Species

    Produce many offspring, little parental care, reproduce early, short lifespan; examples: insects, weeds.

  • K-Selected Species

    Few offspring, extensive parental care, longer lifespan; examples: humans, elephants.

  • Community

    All populations of different species living together in an area.

  • Niche

    The role of a species in its environment, including food sources, habitat, resource use, and reproductive strategies.

  • Symbiosis: Mutualism

    Both organisms benefit (+/+); example: bees and flowers.

  • Symbiosis: Commensalism

    One benefits, other unaffected (+/0); example: barnacles on whales.

  • Symbiosis: Parasitism

    One benefits while harming the host (+/-); examples: ticks, tapeworms.

  • Keystone Species

    Species whose removal greatly changes an ecosystem; example: sea otters.

  • Ecosystem Components

    Includes biotic (living) and abiotic (nonliving) components like plants, animals, water, soil, and sunlight.

  • Producers (Autotrophs)

    Organisms that make their own organic molecules; examples: plants, algae.

  • Consumers (Heterotrophs)

    Obtain energy by eating other organisms.

  • Decomposers

    Break down dead organisms and return nutrients; examples: bacteria, fungi.

  • Eutrophication

    Caused by excess nitrogen and phosphorus, leading to algal blooms, oxygen depletion, and fish kills.

  • Biomes Determined By

    Primarily temperature and precipitation.

  • Primary Succession

    Occurs where no previous community existed; pioneer species colonize first; examples: new volcanic rock.

  • Secondary Succession

    Occurs where a community existed previously; examples: after forest fire or abandoned farmland.

  • Darwin's Main Idea of Natural Selection

    Individuals produce more offspring than survive, compete for resources, and those with advantageous traits survive and reproduce.

  • Hardy-Weinberg Equation

    \(p^2 + 2pq + q^2 = 1\), where p² = homozygous dominant, 2pq = heterozygous, q² = homozygous recessive.