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Population Ecology

Explore the dynamics of populations, from size and density to growth rate and reproductive strategies. Learn about factors influencing population growth and how human populations have evolved over history.

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Population Ecology

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  1. Population Ecology

  2. Population Dynamics • Population: • All the individuals of a species that live together in an area

  3. Population Dynamics • Three Key Features of Populations • Size • Density • Dispersion

  4. Three Key Features of Populations Size: number of individuals in an area

  5. Three Key Features of Populations • Growth Rate: • Birth Rate (natality) - Death Rate (mortality) • How many individuals are born vs. how many die • Birth rate (b) − death rate (d) = rate of natural increase (r)

  6. Three Key Features of Populations Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space

  7. How Do You Affect Density? • Immigration:movement of individuals into a population • Emigration: movement of individuals out of a population • Density-dependent factors:Biotic and abiotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites) • Density-independent factors:Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

  8. How Do Populations Grow? • Idealized models describe two kinds of population growth: • Exponential Growth 2. Logistic Growth

  9. Carrying Capacity (k): The maximum population size that can be supported by the available resources There can only be as many organisms as the environmental resources can support Carrying Capacity

  10. Exponential Growth Curve Figure 35.3A

  11. Logistic Growth Curve

  12. Factors Limiting Growth Rate • Declining birth rate or increasing death rate are caused by several factors including: • Limited food supply • The buildup of toxic wastes • Increased disease • Predation

  13. “Booms” and “Busts”

  14. Reproductive Strategies • R Strategists • Short life span • Small body size • Reproduce quickly • Have many young • Little parental care • Ex: cockroaches, weeds, bacteria

  15. Reproductive Strategies • K Strategists • Long life span • Large body size • Reproduce slowly • Have few young • Provides parental care • Ex: humans, elephants

  16. Age Distribution • Distribution of males and females in each age group of a population • Used to predict future population growth

  17. Human Population Growth • J curve growth • Grows at a rate of about 80 million yearly • r =1.3% • Why doesn’t environmental resistance take effect? • Altering their environment • Technological advances • The cultural revolution • The agricultural revolution • The industrial-medical revolution

  18. The Human Population • Doubled three times in the last three centuries • About 6.1 billion and may reach 9.3 billion by the year 2050 • Improved health and technology have lowered death rates

  19. History of the Human Population

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