The logistic model helps explain how population growth slows as a population approaches its carrying capacity. However, real environments change, and populations interact with other species. This lesson explores the limits of the model and how density-dependent factors regulate population growth.
The carrying capacity is the population size an environment can support over time, given its available resources and conditions. A basic logistic model often treats carrying capacity as constant. In nature, it is not.
All flashcards
Why can carrying capacity change over time?
Seasons, weather, disturbances, and interactions with other species can alter resources and habitat conditions.
What is density-independent regulation?
Regulation by factors whose population-level effects are not determined by population density when they act.
What did studies of Ascaris lumbricoides find about fecundity?
Denser parasite populations had fewer eggs, but female weight did not explain the pattern.
How do intraspecific and interspecific competition differ?
Intraspecific competition is among members of the same species; interspecific competition is between different species.
What do modern demographic-based life-history models add?
They account for age structure and age-specific mortality, along with ecological factors such as resources and competition.
Quiz questions
Why can disease act as a density-dependent factor in a crowded population?Answer: Close contact can make disease transmission more likely.
Two deer populations experience the same harsh winter. Why might the population with more survivors recover sooner?Answer: It may have more potential breeders available to reproduce.
Which explanation best reflects the evidence about woolly mammoth extinction?Answer: Climate and habitat change, hunting, and human migration may have contributed together.
Which combination is commonly associated with K-selected species?Answer: Fewer, larger offspring and greater parental investment.
What makes a factor density-independent?Answer: Its population-level effect is not determined by density when it acts.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.