Population ecology
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Population ecology






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Population ecology Population ecology Presentation Transcript

    • Geographic distribution/ range
    • Population density
    • Population dispersion
    • Immigration
    • Emigration
    • Logistic growth
    • Exponential growth
    • Biotic potential
    • Environmental resistance
    • Carrying capacity
    • Density-dependent factors
    • Density independent factors
    • Geographic distribution
    • Density
    • Dispersion
    • Growth rate
    • Age structure
    What is a population? A population is a group of individuals of the same species occupying the same general area.
    • geographical range of a species or a group of species
    • the suitability of habitats influences the distribution of a species (each species is adapted to a rather limited range of abiotic and biotic conditions)
    Population density
    • the number of individuals per unit area or volume
    • pattern of spacing among individuals in a habitat
    • Types of dispersion:
    • RANDOM
    • - habitat conditions are uniform / resource availability is steady
    • - individuals neither attract nor avoid each other
    • - rare in nature
    • - individuals are evenly spaced in a habitat
    • - due to competition or territorial behavior
    • - species are aggregated in patches
    • - most common in nature because:
    •  cluster around patchy resources
    •  live in social groups
    •  species has limited dispersal powers
    • increase in the size of a population of organisms
    • population size  the number of individuals that contribute to a population’s gene pool
  • For mobile animals  Individuals are captured and marked in some way, then the marked animals are released.  Later, animals are captured and checked for marks.  In the later sample, the proportion of marked individuals should be representative of the proportion marked in the whole population.
    • increase in the size of a population of organisms
    • population size  the number of individuals that contribute to a population’s gene pool
    • Factors that affect population size:
    • 1. Number of births (natality)
    • 2. Number of deaths (mortality)
    • 3. Immigration/Emigration
    • Immigration – the arrival of new residents from other areas
    • Emigration - individuals permanently move out of the population
    • – no overall increase or decrease during a specified interval; population size is stabilized (assuming that immigration and emigration balance each other  number of births = number of deaths)
  • 07/20/10 Free PowerPoint Template from www.brainybetty.com
    • Individuals in population have constant rate of reproduction
    • Over time, becomes infinitely large
    • Under ideal conditions with unlimited resources, population will grow exponentially
      • Ideal condition- abundant space, food, protection against predator and disease
    • Does not continue naturally for a long time
  • 07/20/10 Free PowerPoint Template from www.brainybetty.com Carrying capacity
    • Due to decrease in resources that lead to decrease in population growth
    • Decrease in pop growth maybe caused by decrease in death rate, increase in death rate or the occurrence of both at the same time at the same rate
      • Is also true for emigration and immigration
    • Recall: limiting factors determine the primary productivity of an area
    • In population, a limiting factor causes population growth to decrease
  • Pop size competition predation Parasitism and disease Drought and other climate extremes Human disturbances
    • Depends on the population size
    • Is due to population density
    • Major force of evolution
    • Competition should be decreased
    • Evolution will lead separation of niches
      • No same species can occupy the same niche at any given place and time
    • One of the best population control
      • Characterized by fluctuations of the prey and predator populations
    • Limiting factor that affects the population regardless of its size
      • Characterized by a CRASH in the population size
      • biotic potential/reproduction potential
          • maximum rate of growth of a population
          • conditions are optimal / ideal
          • high reproduction, low mortality
      • environmental resistance
          • factors that limit population growth
          • limiting factors: food, space, O 2 , shelter, accumulation of wastes
      • carrying capacity
          • maximum number of individuals in a population (or species) that a given environment can support indefinitely
          • in the steady state (of logistic growth)  size oscillates around this number
    • Age structure
    • the number of individuals in each of several age categories:
    • 1. prereproductive age – have the potential to produce offspring when they mature
    • 2. reproductive age – actual reproducing members
    • 3. postreproductive age
    •  1 & 2 make up the population’s reproductive base
    • The biotic potential of an ecosystem is affected by environmental resistance, thus resulting in a maximum carrying capacity
    • Understanding patterns in human population growth is important in addressing population problems around the world.