Download POPULATION DYNAMICS

POPULATION DYNAMICS
PART TWO
WHY STUDY POPULATION DYNAMICS?
•Populations
of organisms are dynamic
•Populations with negative growth could lead to species
extinction
•Populations with positive growth could impact local
ecosystems
•Investigating population distribution patterns could
predict ecosystem health, and develop policies and
action plans
POPULATION SIZE VS DENSITY
CRUDE VS ECOLOGICAL DENSITY

Crude density – number of individuals of the same species
per total unit area
10 m
20%

5m
Ecological density – number of individuals of the same
species per unit area or volume actually used by the
individuals
MEASURING POPULATION
CHANGE
•Carrying
capacity
•Factors that affect population
growth
•Patterns in survivorship of
species (survivorship curves)
•Calculating change in population
size
CARRYING CAPACITY (K)
The maximum number of organisms that can
be sustained by available resources over a
limited period of time
 Carrying capacity is dynamic; environmental
conditions are always changing

 Eg
different Ks for two identical populations living in
different habitats
FACTORS AFFECTING POPULATION
GROWTH
Natality (number of births)
 Mortality (number of deaths)
 Immigration (number of individuals that
move into existing population)
 Emigration (number of individuals that move
out of an existing population)

FACTORS AFFECTING POPULATION GROWTH
These factors vary from species to species
 Populations which are stationary are not
affected by immigration and emigration
 Fecundity varies amongst species (potential to
produce large number of offspring)
 Human actions and natural factors also affect
population growth

PATTERNS IN SURVIVORSHIP OF SPECIES
Type I: Low mortality, high life expectancy, small # of offspring eg mammals
Type II: Uniform risk of mortality, age independent of age eg honeybees
Type III: High mortality, low life expectancy, large # of offspring eg sea turtles