Analyze Ecosystem Change Data - Middle School Life Science

What is the term for a nonliving environmental factor such as temperature, rainfall, or pH?

Abiotic factor. Non-living components that influence living organisms in an ecosystem.
Identify the most supported conclusion when a population stabilizes near a horizontal line labeled $K$ .

The population reached carrying capacity ( $K$ ). Growth stops when resources become limiting at carrying capacity.
What is the term for the maximum population size an environment can support long term?

Carrying capacity. Limited by resources like food, water, and space available in the environment.
Which relationship is shown when two species both decrease as they use the same resource?

Competition. Both species need the same limited resource to survive.
What does a population boom followed by a crash most strongly suggest about resources?

Resources were exceeded, then scarcity caused a decline. Overshoot occurs when populations exceed carrying capacity temporarily.
Identify the likely effect on algae if fertilizer runoff increases nutrient levels in a lake.

Algae population increases (algal bloom). Extra nutrients cause rapid algae growth, depleting oxygen for other life.
What is the term for a living environmental factor such as predators, prey, or disease organisms?

Biotic factor. Living components that interact with and affect other organisms.
A lake's phosphorus increases and algae rises sharply; underwater plants decline. What process is shown?

Eutrophication. Excess nutrients cause algae blooms that block light to plants.
After wolves are reintroduced, deer decrease and young trees increase. What interaction explains this?

Predation reduced herbivory, allowing plant recovery. Wolves control deer numbers, reducing browsing pressure on trees.
Which relationship is shown when predator numbers rise shortly after prey numbers rise?

Predator-prey relationship with a time lag. Predators need time to reproduce in response to prey abundance.
What is the term for a relationship in which one benefits and the other is unaffected (+/0)?

Commensalism. One organism benefits while the other experiences no harm or help.
What is the term for a limiting factor whose impact increases as population density increases?

Density-dependent limiting factor. Effects intensify in crowded populations, like disease spread or competition.
Which option best describes this trend: prey rises first, then predator rises, then prey falls?

Predator increase caused prey decline after a time lag. Classic predator-prey cycle showing population oscillations.
What does the term "limiting factor" mean in a population data set?

A resource or condition that restricts population growth. Examples include food, water, space, or predators that control population size.
What is a trophic cascade in population data after a predator is removed?

A chain of population changes across multiple trophic levels. Removing top predators causes ripple effects through food webs.
What is the definition of carrying capacity ( $K$ ) in an ecosystem?

The maximum population an environment can sustainably support. Determined by available resources and environmental conditions.
What is the term for a relationship in which one benefits and one is harmed (+/−)?

Predation. One organism kills and consumes another, like a lion hunting zebra.
Which population change is most likely after an invasive predator is introduced to an island ecosystem?

Native prey populations decrease. New predators consume native prey that lack defenses against them.
Identify the independent variable when a graph shows algae population versus nitrate level.

Nitrate level. The independent variable (x-axis) is manipulated to observe effects.
What is the term for a relationship in which both species benefit (+/+)?

Mutualism. Both organisms gain advantages from their interaction, like bees and flowers.
Which conclusion is best supported if a population levels off near a constant value over time?

The population reached carrying capacity. Population stabilizes when resource limits prevent further growth.
What is the term for the movement of individuals out of a population, decreasing its size?

Emigration. Individuals leave for other areas, reducing population numbers.
Which population change is most likely if a contagious disease spreads more easily as density rises?

Population growth rate decreases. Disease spreads faster in crowded conditions, limiting population growth.
What is the term for a limiting factor that affects populations regardless of density?

Density-independent limiting factor. Affects all individuals equally, like natural disasters or climate events.
What is the term for a relationship in which both species are harmed (−/−) due to shared needs?

Competition. Both organisms suffer when competing for the same limited resources.
Which population change is most likely after a sudden drought reduces plant biomass in a grassland?

Herbivore populations decrease. Less plant food available means fewer herbivores can survive.
Identify the likely predator response if a graph shows a sharp decline in the prey population.

Predator population decreases after a lag. Predators starve when prey becomes scarce, causing delayed decline.
Which option is a density-independent population limiter: drought, disease, or competition?

Drought. Weather events affect populations regardless of their density.
Which conclusion is best supported if births and immigration exceed deaths and emigration for 1 year?

Population size increases. More individuals added than removed results in net population growth.
Choose the best claim: If average temperature rises, a cold-adapted species' range shifts toward what direction?

Toward cooler areas (higher latitude or higher elevation). Species track their optimal temperature zones as climate changes.
A pollutant reduces insect population; bird population falls two months later. What is the likely link?

Food shortage caused the bird decline. Birds depend on insects as their primary food source.
What is the term for the movement of individuals into a population, increasing its size?

Immigration. New individuals join from outside, adding to population numbers.
What is the difference between density-dependent and density-independent factors?

Density-dependent varies with density; density-independent does not. Competition and disease are density-dependent; weather is density-independent.
A fish kill occurs after dissolved oxygen drops from $8$ to $2$ mg/L. What change most likely caused it?

Reduced oxygen availability limited fish survival. Fish require $>4$ mg/L dissolved oxygen to survive.
Which ecosystem change most directly causes a long-term decrease in biodiversity: habitat loss or more rainfall?

Habitat loss. Destroying habitats eliminates species permanently, unlike temporary rain changes.
Which population change is most likely after wolves are removed from an ecosystem with deer and plants?

Deer population increases. Without predators controlling them, prey populations grow rapidly.
Identify the dependent variable when a graph shows rabbit population versus time.

Rabbit population. The dependent variable (y-axis) changes in response to time.

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