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Population Biology

Population Biology. Mouse: - 21 day gestation period - average litter size = 6 - reach reproductive age at 6 weeks House Fly: - female lays 100 eggs (half female) - reach reproductive age at 2-3 weeks. Population Growth. Population = A group of organisms that naturally

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Population Biology

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  1. Population Biology

  2. Mouse: - 21 day gestation period - average litter size = 6 - reach reproductive age at 6 weeks House Fly: - female lays 100 eggs (half female) - reach reproductive age at 2-3 weeks

  3. Population Growth Population = A group of organisms that naturally interbreed and live in a limited space at a given time. Under ideal conditions  Exponential Growth Biotic Potential: Maximum growth rate of population under ideal conditions.

  4. Population Growth Species and DO NOT reproduce at this rate because there are limiting factors. Growth curve looks more like this: Birth rate = death rate

  5. Limiting Factors • Any factor that limits the number of individuals of a population in any ecosystem. • Can be: • Density Dependent (worse when crowded) • Density Independent (not affected by crowdedness) • Abiotic (nonliving) • Biotic (living)

  6. Limiting Factors Space - crowded conditions increase stress and affect hormones/reproduction - density _____________ B. Food - important not to outstrip food supply - density _____________

  7. Limiting Factors C. Predation - feeding of one organism on another - density __________ Predators can improve prey population. How is that possible? Increased prey = increase predators and vice versa

  8. Limiting Factors D. Parasitism - symbiosis between host and parasite - parasite usually doesn’t cause death - density __________ E. Disease - can spread faster in high densities - used by biologists to control pest populations (ex. Myxoma virus – rabbits) - density __________

  9. Limiting Factors F. Interspecific Competition - competition between two different species - density ________ Competitive Exclusion Principle * Two populations CANNOT occupy the same ecological niche without one driving the other to extinction. (results in niche differentiation)

  10. Limiting Factors G. Intraspecific Competition - competition between members of the same species - more intense than interspecific comp. - avoidance via: life cycles (tadpole/frog) seed dispersal (plants) social hierarchies (social animals) - density ____________

  11. Limiting Factors H. Temperature - affects external environment - density ______________ Oxygen - more in aquatic systems - levels critical for survival (ex. Pollution increases bacterial growth, in turn decreases amount of dissolved oxygen) - density ______________

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