Kami Export - Savvas Ch. 2, 22, 23 Population Biology, Communities and Ecosystems, Humans and Global Change (1) (1)

1. Population Ecology

  • Definition: Study of populations in relation to their environment, including environmental influences on:

    • Size and density

    • Age structure

    • Population dynamics

    • Impact on ecosystems

2. Population Dynamics

2.1 Biological Processes

  • Population: A group of individuals of a single species living in a specified area.

  • Density: Number of individuals per unit area or volume.

  • Dispersion: Pattern of spacing among individuals within the population.

2.2 Processes Influencing Population Density

  • Births and Immigration: Add individuals to a population.

  • Deaths and Emigration: Remove individuals from a population.

  • The balance between these processes determines overall density.

3. Patterns of Dispersion

  • Dispersion can be classified in three ways, influenced by resource availability and behavior:

    • Clumped: Individuals are grouped in patches (most common).

    • Uniform: Individuals are evenly spaced.

    • Random: Individuals are distributed unpredictably.

4. Principles of Population Growth

  • Populations grow at different rates, defined by two main types:

4.1 Linear Growth

  • Same amount of organisms added over each time segment.

  • Creates a linear graph.

4.2 Exponential Growth

  • Increasing numbers of organisms added per time segment.

  • Produces a J-shaped growth curve.

  • Example question: Determine the population size using the formula 2^n where n = number of generations.

5. J-Shaped Curve of Exponential Growth

  • Seen in rebounding populations.

    • Example: The elephant population in Kruger National Park, South Africa, after hunting was banned.

6. Logistic Growth Model

  • Exponential growth is often unsustainable.

  • Carrying Capacity (K): Maximum population size that the environment can support.

  • Limits to growth arise from environmental pressures, varying with resource abundance.

7. Demographics

7.1 Definition

  • Demographics: Study of population vital statistics and their changes over time.

  • Important Factors: Birth rates, death rates, age structure.

7.2 Age Structure Profile

  • Example demographics based on population growth:

    • Rapid Growth: Large number of younger individuals.

    • Slow Growth/Stable: Balanced young and adult populations.

    • No Growth/Shrinking: Decline in populations, predominantly older individuals.

8. Population Limiting Factors

8.1 Density-Dependent Factors

  • Factors that intensify as population density increases:

    • Disease

    • Predation

    • Competition

8.2 Density-Independent Factors

  • Affect all populations regardless of density:

    • Natural disasters (fire, floods)

    • Extreme weather conditions

9. Community Interactions and Relations

9.1 Symbiotic Relationships

  • Mutualism: Both species benefit (+,+).

  • Commensalism: One species benefits, the other is unaffected (+,0).

  • Parasitism: One species benefits at the expense of the other (+,-).

10. Biodiversity and Conservation

10.1 Importance of Biodiversity

  • Measures the variety of life in a given area.

    • Tropical rainforests are more diverse than deserts.

  • Biodiversity sustains ecosystems, food webs, and human health.

10.2 Threats to Biodiversity

  • Habitat Loss: Urban development, deforestation.

  • Habitat Fragmentation: Large areas split into smaller patches affecting species survival.

  • Pollution: Air and water pollution degrades ecosystems.

10.3 Conservation Efforts

  • Focus on sustainable development and habitat preservation.

  • Recognize the impact of invasive species and manage resources wisely.