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Population Growth and Regulation

Population Growth and Regulation. Characteristics of Populations. Demographics are characteristics of populations Populations can be characterized by their: Population Size Population Density Population Distribution Age structure Reproductive base # Reproductive and younger.

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Population Growth and Regulation

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  1. Population Growth and Regulation

  2. Characteristics of Populations • Demographics are characteristics of populations • Populations can be characterized by their: • Population Size • Population Density • Population Distribution • Age structure • Reproductive base • # Reproductive and younger

  3. Age Structure Diagram Green - Pre-reproductive years Dark Blue- Reproductive years Light blue - Post- reproductive years

  4. Age Structure Diagram U.S. Zero growth: #births = #deaths and #immigrate = #emigrate

  5. Regarding Population Density: • The same area may be home to many species but they may vary by density • Density refers to the number of individuals in an area but not how they are dispersed • Population density variations are largely due to ecological relationships and organism interactions in an area

  6. Population Size and Exponential Growth: • How population size changes • Size depends on births, immigration, deaths, emigration and migrations • Zero population growth is a near balance between all the positive and negative factors

  7. Ground Zero to Exponential Growth Increase in population of field mice J Shaped Growth Curve

  8. Effects of Deaths on Populations The effects of deaths on the rate of increases in 2 bacterial populations

  9. Regarding the Biotic Potential: • The biotic potential of a population is its maximum rate of increase under ideal conditions • Biotic potentials vary from species to species based on: • What age reproduction begins • How frequent reproduction is • How many offspring are born at a time

  10. Limits on the Growth of Populations: • The actual rate of growth depends on the environmental conditions • Limiting factors are collectively called environmental resistance and include: • Nutrient supply • Predation • Competition for space • Pollution • Metabolic wastes

  11. Limiting Factors on Growth • The sustainable supply of resources defines the carrying capacity for a population in an environment • The capacity can vary over time • Note the S shaped logistic growth

  12. Carrying Capacity

  13. Density - Dependent Controls: • The main controls are: • Competition for resources • Predation • Parasitism • Disease • They exert their effects in proportion to the number of individuals present • Density - dependent factors • Events resulting in more deaths • Fewer births

  14. Paramecium caudatum Paramecium aurelia Fig. 48.4, p. 856

  15. PREY POPULATION PREDATOR POPULATION Fig. 48.7, p. 858

  16. Fig. 48.8, p. 859

  17. Density Independent Factors: • Some events such as weather tend to increase the death rate without respect to the number of individuals present • Lightning, floods, snowstorms affect both large and small populations!

  18. Life History Patterns: • Life Tables • Demography is the study of the age-specific patterns of particular populations • Life tables follow the fate of a group (cohort) and calculate survivorship schedules

  19. A note on… Human Population Growth • Increase in growth rate • Expansion of habitat • Increased capacity in existing habitats • Population has sidestepped limiting factors • Technology • Medicine

  20. Population Growth Rate in Different Regions

  21. Population Growth Rate in Different Regions 1996 - Orange 2025 - Blue

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