Population Dynamics
What is the maximum population size that an environment can support over time based on available resources?
Carrying Capacity
What does population size tell you?
The total number of individuals in a population.
What is a limiting factor?
A factor that restricts the size, growth, or distribution of a population.
Two species compete for the same limited food resource. What type of interaction is this?
Competition
What is genetic variation?
Differences in inherited traits among individuals within a population.
A population has abundant resources and begins increasing very rapidly. What type of growth is most likely occurring?
Exponential growth
A population changes from 300 individuals to 450 individuals. Did the population increase or decrease?
Increase.
Name TWO resources that can limit population growth.
Possible answers include food, water, space, shelter, nutrients, or sunlight.
A hawk catches and eats a mouse. What type of interaction is this?
Predation
Why can genetic variation be important when environmental conditions change?
Some individuals may have traits that help them survive and reproduce under the new conditions.
Name TWO factors that can cause a population to increase.
Births and immigration
A population changes from 800 individuals to 650 individuals. Give ONE possible reason for the decrease.
Possible answers include increased deaths, decreased births, emigration, reduced resources, disease, predation, or another limiting factor.
Is competition for food a density-dependent or density-independent limiting factor?
Density-dependent.
A bee gets nectar from a flower while helping the flower reproduce. What type of interaction is this?
Mutualism
A population of insects contains some individuals that are resistant to a pesticide. The pesticide is applied repeatedly, and the resistant insects survive and reproduce. What process can cause resistance to become more common?
Natural selection.
What generally happens to population growth as a population approaches its carrying capacity?
Population growth slows because resources become limited and limiting factors have a greater effect.
A fish population has these numbers:
2019: 200
2020: 280
2021: 390
2022: 475
2023: 480
2024: 465
What evidence suggests that the population may be approaching carrying capacity?
The population increased rapidly at first but then leveled off around 475–480 and began fluctuating slightly.
Is a hurricane a density-dependent or density-independent limiting factor?
Density-independent.
A tick feeds on a deer and benefits while the deer is harmed. What type of interaction is this?
Parasitism
Explain how an adaptation can increase an organism's chance of survival.
An adaptation is an inherited trait that helps an organism survive and reproduce in its environment. Individuals with helpful traits may be more likely to survive and reproduce.
A population of deer grows rapidly after being introduced to an area with plenty of food and few predators. Several years later, the population levels off. Explain why.
The population initially grows rapidly because resources are abundant. As the population increases, resources such as food, water, space, and shelter become more limited, causing growth to slow and the population to approach carrying capacity.
A graph shows a population increasing slowly, then rapidly, and finally leveling off. What type of population growth does this pattern represent? What does the leveling-off portion suggest?
Logistic growth. The leveling-off suggests the population is approaching its carrying capacity.
Explain the difference between a density-dependent and density-independent limiting factor. Give ONE example of each.
Density-dependent factors have a stronger effect as population density increases, such as competition, disease, or predation. Density-independent factors affect populations regardless of population density, such as droughts, floods, fires, or hurricanes.
A population of mice increases. Predict TWO possible effects this could have on the ecosystem if mice are an important prey species and also eat plants.
The predator populations that eat mice could increase because more food is available. Plant populations could decrease because more mice are feeding on them.
A population of mice lives on both light-colored sand and dark volcanic rock. Hawks can easily see mice that contrast with their surroundings. Explain how natural selection could change the fur-color distribution of the mouse population over many generations.
Mice whose fur better matches their surroundings are less visible to predators and may survive and reproduce more successfully. Over many generations, the inherited fur-color traits that provide better camouflage can become more common in the population.