Introduction to Population Ecology

Overview

• Instructor: Miss Angela
• Video Focus: Introduction to population ecology
• Future Topics: Growth curves, predator-prey relationships, etc.

Key Concepts

What is a Population?

• A group of individuals of the same species in the same place at the same time.
• Can refer to specific locations (e.g., country's population) or general (human population).

Factors Affecting Population Size

1. Births: Positive influence; adds individuals.
2. Deaths: Negative influence; subtracts individuals.
3. Immigration: Positive influence; individuals move into a population.
4. Emigration: Negative influence; individuals leave a population.

Counting Populations

• Challenges: Organisms may not be easy to count due to mobility.

Methods

1. Mark and Recapture (for mobile organisms)

   • Formula:
     • N = estimated population
     • M = first capture total
     • C = second capture total
     • R = marked individuals recaptured
   • Process: Capture, mark, release, recapture, and calculate.
   • Example: Snail population estimation.

2. Quadrat Sampling (for immobile or slow-moving organisms)

   • Uses a 1x1 meter square to determine population density.
   • Process:
     • Randomly select quadrats
     • Count individuals within quadrats
     • Calculate average and multiply by total area
   • Example: Sunflower field estimation.

Carrying Capacity

• Definition: Maximum number of individuals an ecosystem can support.
• Influenced by available resources (food, shelter, space).
• Graph Interpretation:
  • Initial growth followed by leveling at carrying capacity.
  • Potential for overshoot followed by correction.

Environmental Resistance

• Definition: Limits resources available, preventing population overshoot.
• Role in maintaining carrying capacity.

Density Factors

• Density Dependent Factors:
  • Depend on population size.
  • Examples: Food, space, predation, disease.
• Density Independent Factors:
  • Not linked to population size.
  • Examples: Climate, natural disasters.

Terminology Recap

• Population: Group of same species in the same area.
• Births/Deaths: Influence population size positively/negatively.
• Immigration/Emigration: Movement into/out of a population.
• Counting Methods: Mark and recapture, quadrat sampling.
• Carrying Capacity: Ecosystem's support limit.
• Environmental Resistance: Limits growth, defines carrying capacity.
• Density Factors: Dependent (size-related) vs. Independent (external factors).

Conclusion

• Recap of key terms and concepts.
• Encouragement to subscribe and turn on notifications for future videos.