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Limits of Populations

Limits of Populations. Questions for today:. What is Population Dynamics? How does Population Distribution affect Population Dynamics? What variables control Population Growth? What are the differences between Logistic Growth and Exponential Growth?. Population Dynamics.

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Limits of Populations

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  1. Limits of Populations

  2. Questions for today: • What is Population Dynamics? • How does Population Distribution affect Population Dynamics? • What variables control Population Growth? • What are the differences between Logistic Growth and Exponential Growth?

  3. Population Dynamics • There are four major characteristics used to describe populations: • Distribution • Number • Age Structure • Density • Population Dynamics is the study of how these characteristics change is response to environmental pressures.

  4. Population Distribution • Population Distribution is how individuals in populations are distributed or dispersed within a particular area or volume. • Three patterns of Population Distribution: • Clumping (most common) • Uniform • Random

  5. Population Distribution • Why populations Clump • They clump where resources are available • Migrating individuals find resources easier. • Protection from Predators • Hunting is maximized • Reproduction is easier.

  6. Population Growth • There are four variables in Population Growth: • Immigration • Emigration • Births • Deaths • The formula: Population Change = (Births + Immigration) – (Deaths + Emigration)

  7. Populations Age Structure • A population’s Age structure is defined as the proportions of individuals at various ages, and it can affect population growth. • Three terms used to describe ages: • Pre-reproductive (Population may Increase) • Reproductive (Population will Increase) • Postreproductive (Population will Decrease)

  8. Exponential Vs. Logistic Growth • Biotic Potential is the capacity for population growth under IDEAL conditions. • Intrinsic Rate of Increase (r) is the rate at which the population of a species would grow if it had unlimited resources. • Individuals that have a high intrinsic rate: • Reproduce early • Short Generation Time • Reproduce Many Times • Many offspring in each generation

  9. Exponential vs. Logistic Growth • No population can grow indefinitely • Limiting factors • Environmental Resistance is the combination of all factors that act to limit the growth of a population. Biotic Potential + Environment Resistance = CARRYING CAPACITY

  10. Exponential vs. Logistic Growth • Carrying Capacity (K) is the maximum population of a given species that a particular habitat can sustain indefinitely without being degraded. • A population with few limitation can grow exponentially at a fixed rate of 1% or 2% per year. • Exponential growth starts slowly but then accelerates as the population increases. • J-Shaped Curve

  11. Exponential Vs. Logistic Growth • Logistic Growth involves rapid exponential growth followed by a steady decrease in population growth until the population size levels off. • Yields an S shaped or sygmoid curve • Logistic Growth occurs because of environmental resistance. • What happens if that resistance disappears.

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