Population Growth Curves Lecture Notes

Introduction

• Presenter: Miss Angela
• Focus: Population growth curves
• Key Elements:
  • Identifying and interpreting growth curves
  • Phases affected by competition in populations
  • Importance of terminology
• Resources:
  • Grade 11 & 12 study guides available on Miss Angela's website

Types of Growth Curves

1. Exponential Growth

• Characteristics:
  • J-shaped curve
  • Occurs in small, new populations or environments
  • Requires plentiful resources (e.g., water, food, shelter)
  • Initial slow growth due to limited breeding pairs
  • Followed by rapid, exponential increase
  • High birth rate, low death rate
• Examples:
  • Bacteria, rodents, insects (e.g., locusts)
• Drop-off Point:
  • Population explodes then collapses due to resource depletion
  • Seen in breeding cycles like those of locusts

2. Logistic Growth

• Characteristics:
  • S-shaped curve
  • Includes exponential growth followed by stabilization
  • Defined by carrying capacity
• Phases of Logistic Growth:
  • Lag Phase: Slow growth due to few reproducing pairs
  • Exponential Phase: Rapid growth due to abundant resources
  • Transitional Phase: Slowdown in growth as resources become limited
  • Stationary Phase (Plateau): Population stabilizes around carrying capacity
• Overshooting Event:
  • Population exceeds carrying capacity, then corrects itself
• Stability: Achieved when resources balance with population size

Key Terminology

• Carrying Capacity: Maximum individuals ecosystem can support
• Environmental Resistance: Factors limiting population growth (e.g., resources, space)
• Exponential Growth: Rapid increase in population size
• Logistical Growth: Growth that stabilizes after reaching carrying capacity
• Lag Phase: Initial slow growth period
• Accelerating Phase: Fast growth due to ample resources
• Decelerating Phase: Slowing growth as resources dwindle
• Stationary Phase (Plateau): Stable population size near carrying capacity

Examples of Growth in Organisms

• Laboratory Examples: Paramecium, Daphnia (short life cycles, fast growth)
• Wild Examples: Fur seals (longer life cycles, slower growth)

Extinction and Resource Depletion

• Overshoot Consequences:
  • Possible extinction if resources remain depleted
  • Events leading to resource depletion include natural disasters, disease, habitat loss
  • Example scenario: Bacteria in a petri dish with limited resources

Conclusion

• Graphs must be labeled and phases identified
• Importance of understanding growth dynamics in different organisms
• Upcoming focus: Predator-prey cycles and their unique growth patterns

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