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19.1 Understanding Populations

19.1 Understanding Populations. 1. Population Properties. Size (often hard to measure). 1. Population Properties. Size (often hard to measure) Density – amount of population per unit of area (population crowding) # of individuals = population density area (units 2 ).

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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)

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

  4. 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

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

  6. 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

  7. clumped

  8. 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

  9. uniform

  10. 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

  11. random

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

  13. 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)

  14. 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)

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

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

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

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

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

  20. 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

  21. 3. Models of Growth • Logistic • starts off as b> d • levels off as it reaches carrying capacity (K)

  22. 3. Models of Growth • Logistic • starts off as b> d • levels off as it reaches carrying capacity (K)

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

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

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

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

  27. 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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