5 Questions
How does population density typically affect the impact of density-independent factors on a population?
Higher population densities exacerbate the impact of density-independent factors
Which factor is most likely to contribute to the cyclic nature of a population?
Limited resources leading to intraspecific competition
In a scenario of intense intraspecific competition, what would be most likely observed in the population age structure?
A skewed age structure with few individuals in older age groups
Which of the following is an example of a density-independent factor that can influence population dynamics?
Severe weather events like hurricanes or droughts
What is a characteristic feature of populations experiencing a phase of exponential growth?
An increasing rate of growth proportional to the population size
Study Notes
Population Ecology
- Population ecology is used to increase populations of organisms we wish to harvest, decrease populations of pests, and save populations of organisms close to extinction.
- Humans have converted Earth's natural ecosystems to ecosystems that produce goods and services for our own benefit.
Population Cycles
- Some populations of insects, birds, and mammals undergo dramatic fluctuations in density with remarkable regularity, resulting in "booms" and "busts".
- The snowshoe hare and the lynx populations show a rapid increase followed by a sharp decline every 10 years.
- Three main hypotheses for hare cycles: winter food shortages, predator-prey interactions, and a combination of food resource limitation and excessive predation.
The Exponential Population Growth Model
- Exponential population growth describes the expansion of a population in an ideal and unlimited environment.
- Population size of each new generation is calculated by multiplying the current population size by a constant factor representing the birth rate minus the death rate.
- Produces a J-shaped curve typical of exponential growth.
Case Study: European Starlings
- 1890: 60 European starlings released in NYC
- 10 years later: tens of thousands
- 1920s: millions of starlings across New England
- 1970: starlings across entire United States
- European starlings show exponential growth.
The Logistic Population Growth Model
- Most natural environments have a limited supply of resources needed to sustain population growth.
- Population growth is limited by resource availability.
Explore the role of weather change as a density-independent factor limiting the growth of an aphid population and understand population cycles in biological systems. Learn about the fluctuation patterns in populations of insects, birds, and mammals, and how population cycles of certain species like the snowshoe hare and lynx illustrate interconnections within ecosystems.
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