Unit 3 Slides - AP Environmental Science

Unit 3: Populations

1. Learning Objectives and Essential Knowledge

• ERT-3.A: Identify differences between generalist and specialist species.

  • Specialist species thrive in stable habitats but face extinction due to their narrow ecological niches.

  • Generalist species adapt well to changing habitats, leading to a broader ecological niche.

• Suggested Skills: Concept explanation and environmental concepts.

2. Specialist vs. Generalist Species

2.1 Specialist Species

• Narrow ecological niche with limited range of tolerance.

• Specific food requirements (e.g., bamboo).

• Prone to extinction due to:

  • Less adaptability to environmental change.

  • Vulnerable to habitat disturbances.

2.2 Generalist Species

• Broad ecological niche with larger range of tolerance.

• Flexible resource use and high adaptability.

• Better chance of surviving environmental changes and invasive threats.

3. K-selected vs. r-selected Species

3.1 K-selected Species

• Characteristics:

  • Larger size, fewer offspring (e.g., most mammals, birds).

  • High parental investment and care.

  • Long lifespan and low biotic potential.

  • Populations close to carrying capacity (K).

• More vulnerable to disruption from invasive species.

3.2 r-selected Species

• Characteristics:

  • Smaller size and many offspring (e.g., insects, fish).

  • Minimal parental care and shorter lifespans.

  • Quick to reproductive maturity, high biotic potential.

  • Populations fluctuate significantly around carrying capacity.

  • More likely to thrive in rapidly changing environments.

4. Population Dynamics

4.1 Carrying Capacity (K)

• Max number of individuals ecosystem can support based on limiting resources (food, water, habitat).

• Overshoot: When a population exceeds its carrying capacity.

  • Leads to resource depletion and potential population die-off.

• Die-off: Sharp decrease in population size due to overshoot consequences.

4.2 Density-Dependent vs. Density-Independent Factors

• Density-Dependent Factors: Influence population based on size (e.g., competition, food availability).

• Density-Independent Factors: Influence population regardless of size (e.g., natural disasters).

5. Survivorship Curves

• Type I: High survivorship in early life (e.g., humans).

• Type II: Steady death rate throughout (e.g., birds).

• Type III: High mortality early in life (e.g., fish, insects).

6. Human Population Dynamics

6.1 Growth Factors

• Total Fertility Rate (TFR): Average number of children per woman.

  • Higher TFR = faster population growth.

• Relationships Between:

  • TFR and socio-economic factors: education, affluence, healthcare access.

  • High infant mortality rates often lead to higher fertility rates as families have more children to ensure survivorship.

7. Human Development and Population Growth

• Stages of Demographic Transition:

  • Stage 1: High birth and death rates, pre-industrial.

  • Stage 2: Declining death rates, high growth, industrializing.

  • Stage 3: Further decline in birth rates as industrialization completes, stable growth.

  • Stage 4: Very low birth rates and potential population decline in highly developed countries.

8. Conclusion

• Understanding population dynamics, species survival strategies, and human factors affecting growth is crucial for ecological and environmental studies.