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POPULATION PRINCIPLES

POPULATION PRINCIPLES. Chapter 6. OUTLINE. Population Characteristics Population Growth Curve Carrying Capacity Reproductive Strategies (R and K) Human population growth Doubling Time Size. POPULATION CHARATERISTICS.

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POPULATION PRINCIPLES

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  1. POPULATION PRINCIPLES Chapter 6

  2. OUTLINE • Population Characteristics • Population Growth Curve • Carrying Capacity • Reproductive Strategies • (R and K) • Human population growth • Doubling Time • Size

  3. POPULATION CHARATERISTICS • Population - Group of individuals inhabiting the same area simultaneously. • Natality and Mortality • Natality - Number of individuals added through reproduction • Birth Rate (Humans born / 1000)

  4. Mortality - Number of individuals removed via death • Death Rate (Humans Died / 1000) • Sex Ratio - Age Distribution • Sex Ratio- Relative number of males and females in a population. • Age Distribution - Number of individuals of each age in a pop. • Tells HOW a pop willgrow

  5. Population Age Structure Diagrams

  6. Pop. Density and Spatial Distribution • Population Density - Number of individuals per unit area. • Dispersal - Movement of individuals into new areas. • Emigration - Out movement • Immigration - In Movement

  7. Population Growth Curve • Biotic Potential - Reproductive capacity • Generally, biotic potential is much above replacement level. • All living populations follow an exponential growth curve.

  8. Carrying Capacity • Carrying Capacity - Number of individuals of a species than can be indefinitely sustained in a given area.

  9. Environmental Resistance - Any factor (limiting factor) in the environment limiting carrying capacity. Four main factors: • Raw material availability • Energy availability • Waste accumulation and disposal • Organism interaction

  10. Reproductive Strategies • Not all species reach a stable carrying capacity. • Species can be broadly lumped into two categories: • K- strategists • R-strategists

  11. K - Strategists • Large organisms - long-lived • Produce few offspring • Provide substantial parental care • Populations typically stabilize at a carrying capacity. • Reproductive strategy is to invest in a few, quality offspring.

  12. Limited by density - dependent population controls. • Factors that become more severe as the population grows in size. (Diseases) • Deer - Lions - Humans

  13. R - Strategists • Small organisms - Short -lived • Produce many offspring • Little if any parental care • Usually do not reach carrying capacity (boom-bust cycles) • Reproductive strategy is to produce large numbers of offspring to overcome high mortality.

  14. Limited by density-independent population controls. • Populations size is irrelevant to the limiting factor (weather conditions) • Grasshoppers - mice

  15. Human Population Growth • Major reason for increasing human population growth rate is an increase in medical care, and a consequential decrease in death rates.

  16. Doubling Time • Doubling Time of a population (years) : 70 / Population Growth Rate (%) ( 70 / 2.0% = 35 years )

  17. Social Aspects • Humans are social animals who have freedom of choice. • People make decisions based on history, social situations, ethical and religious beliefs, and personal desires.

  18. Ultimate Size ? • United Nations projects human population will reach 10 billion by 2050.

  19. SUMMARY • Population = Group of individuals inhabiting same area at same time • Birth and death rates, sex ratio, age distribution, all affect pop. growth • Population Growth Curves (exponential growth) • Carrying Capacity • R and K reproductive strategies • Human population growth is complex, yet ultimately simple

  20. Just how many people can the earth sustain indefinitely ??

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