Glossary
Carrying Capacity
The maximum population size of a particular species that a given environment can sustainably support indefinitely, given the available resources like food, water, and space.
Example:
A small pond might have a carrying capacity of 50 fish, meaning it can only sustain that many individuals without running out of food or oxygen.
Density-Dependent Factors
Limiting factors whose impact on a population's growth rate increases as the population density increases, often due to competition, predation, or disease.
Example:
The rapid spread of a highly contagious flu virus among students in a crowded dormitory is a classic example of a density-dependent factor affecting population health.
Density-Independent Factors
Limiting factors that affect a population's growth rate regardless of its density or size, typically involving abiotic factors like weather or natural disasters.
Example:
A sudden, severe wildfire that destroys a forest habitat would be a density-independent factor affecting the animal populations living there, regardless of how many animals were present.
Logistic Growth
A population growth model that describes how a population's growth rate slows down as it approaches the carrying capacity of its environment, eventually stabilizing to form an S-shaped curve.
Example:
When bacteria are grown in a limited nutrient broth, their population initially grows fast but then exhibits logistic growth as nutrients become scarce, eventually leveling off.
Logistic Growth Equation
A mathematical formula ($dN/dt = r_{max}N(K-N)/K$) used to model logistic population growth, showing how the population growth rate ($dN/dt$) changes based on the maximum per capita growth rate ($r_{max}$), current population size ($N$), and carrying capacity ($K$).
Example:
Using the logistic growth equation, biologists can predict how quickly a recovering whale population will grow as it approaches its carrying capacity in the ocean, considering the available resources.
Overpopulation
Occurs when a population's size exceeds the carrying capacity of its environment, leading to resource scarcity and negative impacts on the population's health and fitness.
Example:
If a deer population on an island grows too large, it can lead to overpopulation, causing them to deplete all available vegetation and suffer from starvation.