Disturbances Change Populations - Middle School Life Science
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Which statement best describes how a disturbance can change carrying capacity ($K$)?
Which statement best describes how a disturbance can change carrying capacity ($K$)?
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It can reduce or increase available resources, changing $K$. Disturbances alter resource availability, which directly affects carrying capacity.
It can reduce or increase available resources, changing $K$. Disturbances alter resource availability, which directly affects carrying capacity.
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What is primary succession?
What is primary succession?
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Succession starting where no soil exists. Begins on bare rock or lava where organisms must create soil from scratch.
Succession starting where no soil exists. Begins on bare rock or lava where organisms must create soil from scratch.
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What is a population bottleneck caused by a disturbance?
What is a population bottleneck caused by a disturbance?
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A sharp size reduction that lowers genetic variation. Few survivors have limited genetic diversity, affecting future generations.
A sharp size reduction that lowers genetic variation. Few survivors have limited genetic diversity, affecting future generations.
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Identify the best evidence that a disturbance increased food supply for herbivores.
Identify the best evidence that a disturbance increased food supply for herbivores.
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Increased plant biomass or plant cover after the event. More plants mean more food available for animals that eat them.
Increased plant biomass or plant cover after the event. More plants mean more food available for animals that eat them.
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What is the best definition of a disturbance in an ecosystem in population dynamics?
What is the best definition of a disturbance in an ecosystem in population dynamics?
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An event that changes resource availability and alters population size or growth. Disturbances disrupt ecosystems by changing resources that populations need.
An event that changes resource availability and alters population size or growth. Disturbances disrupt ecosystems by changing resources that populations need.
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What is population dynamics?
What is population dynamics?
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Changes in population size and composition over time. Tracks how populations grow, shrink, and change through births, deaths, and migration.
Changes in population size and composition over time. Tracks how populations grow, shrink, and change through births, deaths, and migration.
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What is ecological succession as it relates to disturbances?
What is ecological succession as it relates to disturbances?
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Predictable community change over time after a disturbance. Species replace each other in predictable patterns as ecosystems recover.
Predictable community change over time after a disturbance. Species replace each other in predictable patterns as ecosystems recover.
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Identify the immediate population response most likely after a severe wildfire in a forest.
Identify the immediate population response most likely after a severe wildfire in a forest.
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A rapid decrease in population size. Fire kills organisms and destroys habitat, causing immediate population decline.
A rapid decrease in population size. Fire kills organisms and destroys habitat, causing immediate population decline.
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Which graph pattern best indicates a sudden disturbance: gradual increase or abrupt drop in population size?
Which graph pattern best indicates a sudden disturbance: gradual increase or abrupt drop in population size?
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Abrupt drop in population size. Sudden disturbances cause immediate deaths, shown as sharp population drops.
Abrupt drop in population size. Sudden disturbances cause immediate deaths, shown as sharp population drops.
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Which evidence best shows a disturbance caused a population decline: lower births or higher immigration?
Which evidence best shows a disturbance caused a population decline: lower births or higher immigration?
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Lower births. Fewer births directly reduces population, while immigration adds individuals.
Lower births. Fewer births directly reduces population, while immigration adds individuals.
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Which option is density-independent: drought or competition for food?
Which option is density-independent: drought or competition for food?
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Drought. Weather events affect populations equally regardless of how crowded they are.
Drought. Weather events affect populations equally regardless of how crowded they are.
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Which option is density-dependent: disease spread or a hurricane?
Which option is density-dependent: disease spread or a hurricane?
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Disease spread. Diseases spread faster in crowded populations, making it density-dependent.
Disease spread. Diseases spread faster in crowded populations, making it density-dependent.
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What is carrying capacity ($K$)?
What is carrying capacity ($K$)?
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The largest population an environment can support long term. Limited by resources like food, water, and space available in the environment.
The largest population an environment can support long term. Limited by resources like food, water, and space available in the environment.
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Which disturbance most likely leads to secondary succession: volcanic lava flow or a forest fire?
Which disturbance most likely leads to secondary succession: volcanic lava flow or a forest fire?
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A forest fire. Fire leaves soil intact, while lava creates bare rock requiring primary succession.
A forest fire. Fire leaves soil intact, while lava creates bare rock requiring primary succession.
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What is secondary succession?
What is secondary succession?
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Succession after a disturbance where soil remains. Recovery is faster because soil and seeds already exist in the area.
Succession after a disturbance where soil remains. Recovery is faster because soil and seeds already exist in the area.
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Which evidence most strongly supports that a disturbance reduced habitat: fewer nesting sites or more predators?
Which evidence most strongly supports that a disturbance reduced habitat: fewer nesting sites or more predators?
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Fewer nesting sites. Lost nesting sites directly show habitat destruction, unlike predator changes.
Fewer nesting sites. Lost nesting sites directly show habitat destruction, unlike predator changes.
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What is population density?
What is population density?
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Number of individuals per unit area or volume. Measures crowding, which affects competition and resource availability.
Number of individuals per unit area or volume. Measures crowding, which affects competition and resource availability.
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Which measurement is best evidence of a population increase after a disturbance: higher survival rate or lower emigration?
Which measurement is best evidence of a population increase after a disturbance: higher survival rate or lower emigration?
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Higher survival rate. More individuals surviving directly increases population size.
Higher survival rate. More individuals surviving directly increases population size.
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A storm kills many trees. Which population change is most likely for a bird that nests in trees?
A storm kills many trees. Which population change is most likely for a bird that nests in trees?
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Decrease due to reduced nesting sites. Birds need trees for breeding and shelter.
Decrease due to reduced nesting sites. Birds need trees for breeding and shelter.
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A drought reduces plant biomass. Which change is most likely for an herbivore population?
A drought reduces plant biomass. Which change is most likely for an herbivore population?
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Decrease due to reduced food availability. Herbivores depend directly on plants for food.
Decrease due to reduced food availability. Herbivores depend directly on plants for food.
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A new predator is introduced. Which evidence best shows it caused the prey decline?
A new predator is introduced. Which evidence best shows it caused the prey decline?
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Prey decline begins after predator arrival; predation marks increase. Temporal correlation and physical evidence link cause to effect.
Prey decline begins after predator arrival; predation marks increase. Temporal correlation and physical evidence link cause to effect.
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A disease spreads faster as population density rises. What type of limiting factor is this?
A disease spreads faster as population density rises. What type of limiting factor is this?
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Density-dependent limiting factor. Its impact increases with population density.
Density-dependent limiting factor. Its impact increases with population density.
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Choose the best claim supported by evidence: after a flood, insects increased and birds increased later.
Choose the best claim supported by evidence: after a flood, insects increased and birds increased later.
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Birds increased due to more insect prey after the flood. Flood created conditions favoring insects, which feed birds.
Birds increased due to more insect prey after the flood. Flood created conditions favoring insects, which feed birds.
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A disturbance reduces a rabbit population from $200$ to $50$. What is the percent decrease?
A disturbance reduces a rabbit population from $200$ to $50$. What is the percent decrease?
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$75%$ decrease. Calculate: $(200-50)/200 imes 100 = 75%$.
$75%$ decrease. Calculate: $(200-50)/200 imes 100 = 75%$.
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Identify the best evidence that a disturbance lowered birth rate rather than increased death rate.
Identify the best evidence that a disturbance lowered birth rate rather than increased death rate.
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Fewer juveniles per adult with similar adult survival. Adults survived but reproduced less successfully.
Fewer juveniles per adult with similar adult survival. Adults survived but reproduced less successfully.
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