Ecology is similar to physiology: Understanding involves zooming in and out at different levels.
Focus on different scales: Groups within a species (population ecology), groups of different organisms (community ecology), and interactions within an ecosystem (ecosystem ecology).
Population Ecology
Definition: Study of groups within a species interacting in a specific geographic area.
Importance: Understanding population differences over time and place can be useful, e.g., disease outbreaks.
Example: West Nile virus outbreak in Dallas, Texas, 2012 vs 2011.
Key Concepts in Population Ecology
Population Characteristics
Density: Number of individuals in an area (e.g., mosquitoes in Dallas).
Dispersion: Geographic arrangement of individuals (clumped, evenly spaced, random).
Population Growth
Influenced by birth, death, immigration, and emigration.
Fecundity: Number of offspring an individual can have in a lifetime.
Mosquitoes: 2,000 offspring in two weeks vs. Black rhino: 5 offspring in 40 years.
Limiting Factors
Density-Dependent: Growth inhibited by population size (e.g., food scarcity, disease).
Density-Independent: Growth inhibited by external factors (e.g., climate, catastrophes).
Case Study: Mosquitoes in Dallas, 2012
Limiting Factors Removed:
Temperature: Hot weather accelerated mosquito life cycle.
Space: Drought led to stagnant water ideal for breeding.
Impact: Population growth due to favorable conditions.
Carrying Capacity
Definition: Maximum number of individuals a habitat can support.
Density-Dependent Limitations: Affect growth rate as carrying capacity is reached.
Population Growth Models
Exponential Growth
Population grows proportionally to its size until a limiting factor intervenes.
Logistic Growth
Population growth slows as it reaches carrying capacity, creating a plateau.
Mathematical Equation for Population Growth
Calculation: Growth rate (r) = (Number of births - Number of deaths) / Initial population size (N).
Hypothetical Example: Dallas mosquitoes, growth rate of 999 (99,800% increase in population over two weeks).
Conclusion
Understanding population ecology is crucial for managing ecological issues, such as disease outbreaks.
Invitation to explore further topics in ecology in upcoming sessions.