Evaluate Population Explanations - Middle School Life Science
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What is the difference between a density-dependent and a density-independent limiting factor?
What is the difference between a density-dependent and a density-independent limiting factor?
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Density-dependent varies with density; density-independent does not. Competition/disease increase with crowding; weather/disasters affect all equally.
Density-dependent varies with density; density-independent does not. Competition/disease increase with crowding; weather/disasters affect all equally.
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What is carrying capacity (K) in an ecosystem?
What is carrying capacity (K) in an ecosystem?
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Maximum population size the environment can support long term. Limited resources prevent indefinite growth.
Maximum population size the environment can support long term. Limited resources prevent indefinite growth.
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Which option is a density-dependent factor: drought or disease?
Which option is a density-dependent factor: drought or disease?
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Disease. Spreads faster in crowded populations.
Disease. Spreads faster in crowded populations.
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Which option is a density-independent factor: hurricane or competition?
Which option is a density-independent factor: hurricane or competition?
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Hurricane. Affects populations regardless of their density.
Hurricane. Affects populations regardless of their density.
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What does a predator-prey cycle typically look like in population data over time?
What does a predator-prey cycle typically look like in population data over time?
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Prey peaks first; predator peaks later; both oscillate. Predators lag behind prey abundance changes.
Prey peaks first; predator peaks later; both oscillate. Predators lag behind prey abundance changes.
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Identify the best explanation if prey declines first and predator declines shortly after.
Identify the best explanation if prey declines first and predator declines shortly after.
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Prey limitation causing a lagged predator decline. Predators starve when prey becomes scarce.
Prey limitation causing a lagged predator decline. Predators starve when prey becomes scarce.
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What does a trophic cascade mean in an ecosystem?
What does a trophic cascade mean in an ecosystem?
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A change at one trophic level causes changes across other levels. Effects ripple through the food web.
A change at one trophic level causes changes across other levels. Effects ripple through the food web.
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Which explanation best fits: a new top predator arrives and herbivores decrease?
Which explanation best fits: a new top predator arrives and herbivores decrease?
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Increased predation pressure on herbivores. Direct predation reduces prey numbers.
Increased predation pressure on herbivores. Direct predation reduces prey numbers.
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What is the main evidence that competition is limiting a population?
What is the main evidence that competition is limiting a population?
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Reduced growth or survival as density increases due to shared resources. Competition intensifies when resources become scarce.
Reduced growth or survival as density increases due to shared resources. Competition intensifies when resources become scarce.
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Which pattern most supports resource limitation: stable habitat but gradual leveling of growth?
Which pattern most supports resource limitation: stable habitat but gradual leveling of growth?
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Population approaches carrying capacity ($K$). Growth slows as resources become limiting.
Population approaches carrying capacity ($K$). Growth slows as resources become limiting.
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What is a biotic factor that can change population size?
What is a biotic factor that can change population size?
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A living influence such as predation, disease, or competition. Living organisms affect population dynamics.
A living influence such as predation, disease, or competition. Living organisms affect population dynamics.
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What is an abiotic factor that can change population size?
What is an abiotic factor that can change population size?
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A nonliving influence such as temperature, rainfall, or fire. Physical environment affects survival.
A nonliving influence such as temperature, rainfall, or fire. Physical environment affects survival.
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Which explanation best fits: sudden crash in many species after a wildfire?
Which explanation best fits: sudden crash in many species after a wildfire?
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Density-independent disturbance affecting the ecosystem. Fire kills regardless of population density.
Density-independent disturbance affecting the ecosystem. Fire kills regardless of population density.
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Which evidence best supports migration (immigration/emigration) as the cause of change?
Which evidence best supports migration (immigration/emigration) as the cause of change?
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Population shifts without matching changes in births, deaths, or resources. Movement explains changes without birth/death rate shifts.
Population shifts without matching changes in births, deaths, or resources. Movement explains changes without birth/death rate shifts.
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Identify the best explanation if births and deaths stay similar but the count increases sharply.
Identify the best explanation if births and deaths stay similar but the count increases sharply.
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Immigration into the population. New individuals entering increases population.
Immigration into the population. New individuals entering increases population.
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What is the most direct sign that a disease outbreak caused a population decline?
What is the most direct sign that a disease outbreak caused a population decline?
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High mortality with symptoms or pathogen presence in many individuals. Disease shows specific symptoms and spreads.
High mortality with symptoms or pathogen presence in many individuals. Disease shows specific symptoms and spreads.
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Which option best supports overharvesting as the cause: more predators or increased hunting?
Which option best supports overharvesting as the cause: more predators or increased hunting?
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Increased hunting. Human harvest directly removes individuals.
Increased hunting. Human harvest directly removes individuals.
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Which explanation is best if a pollutant increases and multiple species decline together?
Which explanation is best if a pollutant increases and multiple species decline together?
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Abiotic stress from pollution reducing survival and reproduction. Toxins harm all exposed species similarly.
Abiotic stress from pollution reducing survival and reproduction. Toxins harm all exposed species similarly.
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Which relationship is shown when predator numbers rise after prey numbers rise, with a time lag?
Which relationship is shown when predator numbers rise after prey numbers rise, with a time lag?
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Predator–prey cycle with predator lag. Predators increase after prey increases because they need time to reproduce.
Predator–prey cycle with predator lag. Predators increase after prey increases because they need time to reproduce.
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Which type of evidence best supports a claim about why a population changed: long-term population counts or a single observation?
Which type of evidence best supports a claim about why a population changed: long-term population counts or a single observation?
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Long-term population counts (time-series data). Time-series data shows patterns and changes over time, not just one moment.
Long-term population counts (time-series data). Time-series data shows patterns and changes over time, not just one moment.
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What is the dependent variable when you investigate why a population size changed in an ecosystem?
What is the dependent variable when you investigate why a population size changed in an ecosystem?
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Population size (number of individuals). The dependent variable is what you measure (population) in response to changes.
Population size (number of individuals). The dependent variable is what you measure (population) in response to changes.
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What is the independent variable when testing the effect of food on a consumer population?
What is the independent variable when testing the effect of food on a consumer population?
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Food availability (resource level). The independent variable is what you manipulate or test (food) to see its effect.
Food availability (resource level). The independent variable is what you manipulate or test (food) to see its effect.
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Which option is a density-dependent limiting factor: drought or disease spread in crowded conditions?
Which option is a density-dependent limiting factor: drought or disease spread in crowded conditions?
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Disease spread in crowded conditions. Density-dependent factors affect populations more as density increases.
Disease spread in crowded conditions. Density-dependent factors affect populations more as density increases.
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Which option is a density-independent limiting factor: wildfire or competition for mates?
Which option is a density-independent limiting factor: wildfire or competition for mates?
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Wildfire. Density-independent factors affect populations regardless of their density.
Wildfire. Density-independent factors affect populations regardless of their density.
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What term describes the maximum population size an environment can support over time?
What term describes the maximum population size an environment can support over time?
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Carrying capacity. Limited by resources like food, water, and space available in the environment.
Carrying capacity. Limited by resources like food, water, and space available in the environment.
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