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19.1 Understanding Populations

This article provides an overview of population properties, including size, density, and dispersion. It explains the different spatial organizations of populations, such as clumped, uniform, and random dispersion. The article also discusses survivorship curves and models of population growth, including exponential and logistic growth. Additionally, it explores the factors that regulate population growth, including density-independent and density-dependent factors.

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19.1 Understanding Populations

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  1. 19.1Understanding Populations

  2. 1. Population Properties • Size (often hard to measure) • Density– amount of population per unit of area (population crowding) # of individuals = population density area (units2) • Dispersion – spatial organization of the population

  3. 1. Population Properties • Dispersion – spatial organization of the population

  4. 1. Population Properties • Dispersion – spatial organization of the population • Clumped – population is clustered together, usually around resources or from social behavior • ex/ school of fish

  5. clumped

  6. 1. Population Properties • Dispersion – spatial organization of the population • Uniform – the population is evenly dispersed from each other usually from social interactions • ex/ bird nesting sites or solitary predators

  7. uniform

  8. 1. Population Properties • Dispersion – spatial organization of the population • Random – the population is randomly scattered throughout the area • ex/ trees in a forest with seeds dispersed by wind or animals

  9. random

  10. 2. Survivorship Curves • Survivorship Curve • probability of individuals surviving to a certain age

  11. 2. Survivorship Curves • Survivorship Curve • probability of individuals surviving to a certain age I – Low birth rate, low infant mortality, survives to old age (Humans & large mammals)

  12. 2. Survivorship Curves II – Survivorship rate equal at all ages (Birds & reptiles)

  13. 2. Survivorship Curves III – High birth rate, high infant mortality rate (Fish, Insects, Plants)

  14. 3. Models of Growth • Exponential • birth and death rates are constant (b > d)

  15. 3. Models of Growth • Exponential • birth and death rates are constant (b > d) • the rate increases as the population gets larger • limited by density-independent factors • Ex: Bacteria

  16. 3. Models of Growth • Logistic • (K): the number of individuals the environment can support over time. • This is when b rates equal d rates (zero population growth) • limited by density-dependent factors

  17. Most organisms such as seals, and whales follow this model

  18. 4. Regulating Population Growth • Limiting factors: restrains population growth

  19. 4. Regulating Population Growth • Limiting factors: restrains population growth (2 types) • Density-independent factors: no regard for population density EX. Weather, seasons, natural disasters

  20. 4. Regulating Population Growth • Density-dependent factors: increase or become more prominent when the population density increases EX. predation, pollution, food shortage

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