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
      • UNIFORM
      • - individuals are evenly spaced in a habitat
      • - due to competition or territorial behavior
      • CLUMPED
      • - 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.