Population ecologists use mathematical models to describe how population sizes change and to help predict future changes. This lesson introduces exponential growth, a model for populations that have abundant resources, and explains how birth and death rates shape population growth.
In 1798, Thomas Malthus argued that populations can grow rapidly when resources are unlimited. His ideas influenced Charles Darwin’s thinking about population pressure and the struggle for existence. Exponential growth describes this rapid increase when conditions allow individuals to reproduce without resource shortages limiting them.
All flashcards
What is exponential growth?
A pattern of population increase in which growth accelerates as the reproducing population grows, typically under ideal conditions with abundant resources.
What curve represents exponential growth?
A J-shaped curve, formed when population size increases at an accelerating rate over time.
What is the intrinsic rate of increase, r?
The per capita rate of population growth under ideal conditions, calculated as the difference between per capita birth and death rates: r=b−d.
What is carrying capacity?
The largest population size an environment can support under particular conditions, represented by K.
What is intraspecific competition?
Competition between individuals of the same species for resources such as food, space, or mates.
Quiz questions
In a flask with abundant nutrients, 1,000 bacteria double each hour. Why does the number added each hour increase?Answer: Each hour, a larger population is available to reproduce.
In the equation r=b−d, what does r represent?Answer: The per capita difference between birth and death rates.
If per capita birth and death rates are equal, what does the basic population-growth model predict?Answer: Zero net growth, with population size remaining unchanged.
According to the logistic model, what happens when population size N exceeds carrying capacity K?Answer: The model predicts a negative growth rate.
Why may wild populations fluctuate above and below carrying capacity?Answer: Changing conditions and resource availability affect survival and reproduction.
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.