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Understanding Populations

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Understanding Populations Author: Central High School Last modified by: Central High School Created Date: 8/14/2006 12:49:18 PM ... Phenix City Schools – PowerPoint PPT presentation

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Title: Understanding Populations


1
Understanding Populations
  • How Populations Change in Size

2
Objectives
  • Describe the three main properties of a
    population
  • Describe exponential population growth
  • Describe how the reproductive behavior of
    individuals can affect the growth rate of the
    population
  • Explain how population sizes in nature are
    regulated

3
Population
  • A group of organisms of the same species that
    live in the same geographical area
  • Interbreeding
  • Refers to size and number

4
Properties of a Population
  • Density- Number of individuals living in a given
    unit of area
  • Dispersion- Pattern of distribution of organisms
    in an area
  • Random
  • Clumped
  • Even
  • Describe populations and used to predict changes

5
How do Populations Grow?
  • Growth rate- Increase in the size of an organism
    or population over time
  • Positive- Births outnumber deaths
  • Negative- Deaths outnumber births
  • Zero- Births and deaths are equal

6
Reproductive Potential
  • Reproductive potential- Maximum number of
    offspring that an organism can produce
  • Increases
  • More offspring produced at a time
  • Reproduction begins earlier in life
  • Generation time- Average time it takes to reach
    age at which members of a population begin
    reproducing
  • Biotic potential- Fastest rate at which a
    population can grow
  • Limited by reproductive potential
  • Large organisms
  • Long generation time
  • Slow population growth
  • Small organisms
  • Short generation time
  • Fast population growth

7
Exponential Growth
  • Growth in which numbers increase by a certain
    factor in successive time periods
  • Plenty of food and space
  • No competition or predators

8
What Limits Population Growth?
  • Carrying Capacity- The maximum population that an
    ecosystem can support indefinitely
  • Estimated by observing population crashes
  • Ex Rabbits introduced into Australia in 1859

9
What Limits Population Growth?
  • Limiting resource- Natural resource that is
    consumed at the same rate at which the ecosystem
    produces it
  • Competition
  • Compete for mates, food, and homes
  • Territory- An area defended by one or more
    individuals

10
Two Types of Population Regulation
  • Density Independent- A certain proportion of a
    population may die regardless of the populations
    density
  • Severe weather and natural disasters
  • Density dependent- Deaths occur more quickly in
    crowded conditions
  • Limited resources, predation, and disease
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