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NEW AIM: How do scientists describe population growth?

NEW AIM: How do scientists describe population growth?. Population Ecology. - The study of changes in population size and the factors that regulate it. Population. - group of individuals of a single species that occupy the same general area. 1. Rely on same resources.

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NEW AIM: How do scientists describe population growth?

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  1. NEW AIM: How do scientists describe population growth? Population Ecology - The study of changes in population size and the factors that regulate it. Population - group of individuals of a single species that occupy the same general area 1. Rely on same resources 2. Influenced by the same biotic and abiotic factors 3. High likelihood of interbreeding

  2. AIM: How do scientists describe population growth? Let’s look at population growth of bacteria starting from a single bacterium - binary fission every 20 minutes under ideal conditions Q: How many will there be after 36 hours?

  3. AIM: How do scientists describe population growth? 2n Where n = # of divisions Let’s look at population growth of bacteria starting from a single bacterium - binary fission every 20 minutes under ideal conditions Q: How many will there be after 36 hours? A: 2108 (enough to cover the planet one foot deep) Graph it:

  4. AIM: How do scientists describe population growth? 1. Exponential Growth Model (J-shaped curve) What does the rate of growth depend on in this model? The number of individuals ONLY So why is Earth not covered in bacteria?

  5. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth Ex. Fur seals on St. Paul Island

  6. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth Ex. Fur seals on St. Paul Island 1. Uncontrolled hunting until 1925 2. Population jumped until 1935 - Almost exponential 3. Population stabilized - Some hunting - limited breeding grounds

  7. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth 3. Logistic Growth Model (S - shaped curve) Q: How does the logistic model differ from the exponential model?

  8. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth 3. Logistic Growth Model (S - shaped curve) Q: How does the logistic model differ from the exponential model? A: It accounts for limiting factors in the environment

  9. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth 3. Logistic Growth Model (S - shaped curve) Carrying capacity (K) - max. population the environment can support without degrading the habitat Determined by: The species itself and the environment (resources available, predation, etc…)

  10. AIM: How do scientists describe population growth? 2. Population limiting factors - environmental factors that restrict population growth 3. Logistic Growth Model When is growth rate the lowest? 1. When population is small or large Limited number of individuals and then limited resources When is it the highest? 1. Population at intermediate level relative to carrying capacity. 2. Plenty of resources NO POPULATION FITS EITHER MODEL PERFECTLY

  11. AIM: How do scientists describe population growth? Population limiting factors - environmental factors that restrict population growth Human Population We have a major problem here. What is our future? The number one problem on this planet for humans and many, many other species is our own overpopulation. What is the solution?

  12. AIM: How do scientists describe population growth? Review Population ecology Exponential growth model - J-shaped - NO limiting factors - Growth rate determined by population size and type of organism Logistic Growth Model - S-shaped - Population limiting factors NO POPULATION FITS EITHER MODEL PERFECTLY

  13. AIM: How do scientists describe population growth? Let’s look at some specific population limiting factors and examples.

  14. NEW AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors a. Competition among members (intraspecific) - food supply, water, space, energy (oil), mates, etc… Song Sparrow Population Experiment (small island in British Columbia) - add food - Clutch size increased Fig. 35.4A

  15. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors a. Competition among members (intraspecific) - food supply, water, space, energy (oil), mates, etc… Competition for space…

  16. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors a. Competition among members (intraspecific) i. food supply ii. space (territory) A. Dispersion patterns 1. clumped 2. uniform 3. random

  17. AIM: What are some of the factors that limit population growth? Dispersion patterns

  18. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors b. Health - increased spread of disease with increased pop. density - accumulation of waste

  19. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors c. Predation As the hare population increases, so does the Lynx population, which will cause the hare population to decrease and in turn the lynx population decreases, etc… “boom-and-bust” cycles Fig. 35.5

  20. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors d. Physiological factors White-footed mouse experiment 1. Enclose in a small field 2. Reproduce quickly to 30 or 40 3. Reproduction declines and pop. stabilizes around 40 4. Add more food and water - no change RESULT: high population induces stress syndrome (hormonal changes) - sexual maturity delayed, reproductive organs shrink, depressed immune system

  21. AIM: What are some of the factors that limit population growth? Population limiting factors 2. Abiotic factors a. Climate and weather Ex. Aphids Fig. 35.4B - insects that feed on phloem sap of plants 1. Exponential growth in spring 2. Rapid die out in hot, dry summer 3. A few individuals survive and reproduce when conditions improve What happens to mosquitoes and grasshoppers during winter? - die out completely, leaving only fertilized eggs

  22. AIM: What are some of the factors that limit population growth? Population limiting factors 2. Abiotic factors b. Fire, flood, etc…

  23. AIM: What are some of the factors that limit population growth? Population limiting factors 1. Biotic factors a. Competition among members - food supply - space Fig. 35.4C b. Health c. Predation d. Physiological factors 2. Abiotic factors a. Climate and weather b. Natural disasters (25-year study of the song sparrow) Almost all populations are regulated by a mixture of these and other factors

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