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2.6.1 .2

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2.6.1 .2

  1. 1. 2.6.1-.2 Populations 5/11/2013 Author-Guru IB/ESS 1
  2. 2. Population Growth change in the size of a population over time. 5/11/2013 Author-Guru IB/ESS 2
  3. 3. • POPULATION = a group of interbreeding organisms (same species) that live in the same place at the same time and compete for the same resources. • Resources = food, water, shelter, mates, and so on . . . • pop. size • 5/11/2013 resources  resources  pop. size Author-Guru IB/ESS 3
  4. 4. Populations change in response to environmental stress or changes in environmental conditions. 1. In size = # of individuals 2. Density = # of individual / specific space 3. Age distribution = proportions / age group 4. Dispersion = 5/11/2013 Clumped (elephants) Uniform Author-Guru IB/ESS (creosote bush) Random (dandelions) 4
  5. 5. 5/11/2013 Author-Guru IB/ESS 5
  6. 6. No population can grow indefinitely! Number of sheep (millions) Every environment has a CARRYING CAPACITY = the maximum number of individuals of a given species that can be sustained indefinitely in 2.0 a given space. 5/11/2013 1.5 1.0 .5 Author-Guru 1800 IB/ESS 1825 1850 1875 Year 1900 1925 6
  7. 7. Factors that affect carrying capacity: 1. Competition with/in and between species. 2. Natural and human caused catastrophes. 3. Immigration and emigration. 4. Seasonal fluctuations in food, water, shelter, and nesting sites. 5/11/2013 Author-Guru IB/ESS 7
  8. 8. A population that has few if any resource limitations grows exponentially. EXPONENTIAL GROWTH starts out slowly and then proceeds faster and faster as the population increases. 5/11/2013 Population size (N) “J” population growth curve Author-Guru IB/ESS Time (t) 8
  9. 9. Bacteria population 24 hours later 1024 8 5/11/2013 Author-Guru IB/ESS 9
  10. 10. 5/11/2013 Author-Guru IB/ESS 10
  11. 11. LOGISTIC GROWTH involves initial exponential growth and then there is a steady decrease in growth as the population encounters environmental resistance and approaches carrying capacity and levels off. “S or sigmoid” population growth curve 5/11/2013 Author-Guru Population size (N) K IB/ESS Time (t) 11
  12. 12. Plateau phase K Population size (N) Transitional phase 5/11/2013 Exponential phase Time (t) Author-Guru IB/ESS 12
  13. 13. Number of reindeer 2,000 1,500 1,000 500 1910 5/11/2013 1920 1930 Author-Guru Year IB/ESS 1940 1950 13
  14. 14. Kaibab Plateau 5/11/2013 Author-Guru IB/ESS 14
  15. 15. Kaibab Plateau 5/11/2013 Author-Guru IB/ESS 15

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