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Population Growth and Regulation

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Title: Population Growth and Regulation


1
Population Growth and Regulation
2
Characteristics of Populations
  • Demographics are characteristics of populations
  • Populations can be characterized by their
  • Population Size
  • Population Density
  • Population Distribution
  • Age structure
  • Reproductive base
  • Reproductive and younger

3
Age Structure Diagram
Green - Pre-reproductive years Dark Blue-
Reproductive years Light blue - Post-
reproductive years
4
Age Structure Diagram U.S.
Zero growth births deaths and immigrate
emigrate
5
Regarding Population Density
  • The same area may be home to many species but
    they may vary by density
  • Density refers to the number of individuals in an
    area but not how they are dispersed
  • Population density variations are largely due to
    ecological relationships and organism
    interactions in an area

6
Population Size and Exponential Growth
  • How population size changes
  • Size depends on births, immigration, deaths,
    emigration and migrations
  • Zero population growth is a near balance between
    all the positive and negative factors

7
Ground Zero to Exponential Growth
Increase in population of field mice
J Shaped Growth Curve
8
Effects of Deaths on Populations
The effects of deaths on the rate of increases in
2 bacterial populations
9
Regarding the Biotic Potential
  • The biotic potential of a population is its
    maximum rate of increase under ideal conditions
  • Biotic potentials vary from species to species
    based on
  • What age reproduction begins
  • How frequent reproduction is
  • How many offspring are born at a time

10
Limits on the Growth of Populations
  • The actual rate of growth depends on the
    environmental conditions
  • Limiting factors are collectively called
    environmental resistance and include
  • Nutrient supply
  • Predation
  • Competition for space
  • Pollution
  • Metabolic wastes

11
Limiting Factors on Growth
  • The sustainable supply of resources defines the
    carrying capacity for a population in an
    environment
  • The capacity can vary over time
  • Note the S shaped logistic growth

12
Carrying Capacity
13
Density - Dependent Controls
  • The main controls are
  • Competition for resources
  • Predation
  • Parasitism
  • Disease
  • They exert their effects in proportion to the
    number of individuals present
  • Density - dependent factors
  • Events resulting in more deaths
  • Fewer births

14
Paramecium caudatum
Paramecium aurelia
Fig. 48.4, p. 856
15
PREY POPULATION
PREDATOR POPULATION
Fig. 48.7, p. 858
16
Fig. 48.8, p. 859
17
Density Independent Factors
  • Some events such as weather tend to increase the
    death rate without respect to the number of
    individuals present
  • Lightning, floods, snowstorms affect both large
    and small populations!

18
Life History Patterns
  • Life Tables
  • Demography is the study of the age-specific
    patterns of particular populations
  • Life tables follow the fate of a group (cohort)
    and calculate survivorship schedules

19
A note on Human Population
Growth
  • Increase in growth rate
  • Expansion of habitat
  • Increased capacity in existing habitats
  • Population has sidestepped limiting factors
  • Technology
  • Medicine

20
Population Growth Rate in Different Regions
21
Population Growth Rate in Different Regions
1996 - Orange 2025 - Blue
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