Transcript Ch.4 Populations

Population Dynamics
Section 4.1, p.92
4/12/2016
Population Dispersion
-How individuals are spaced within an area
Population Density

Number of organisms per unit area
Population Limiting Factors

Density-dependent
• Deaths occur more quickly in a crowded
population
• Ex: resources, predation, disease

Density-independent
• A certain proportion dies regardless of
population density
• Ex: severe weather, natural disaster
Predation – what happened to the
moose population as the wolf
population increased?
Population Growth Rate


How fast a given population grows
Most look at birth rate and death rate
Factors Affecting Growth Rate of
a Population

Natality – number of births
Mortality – number of deaths

Emigration – leaving or exiting

a population
I
 mmigration – moving
population
into a
Carrying Capacity


Max # of individuals of any species
that can be supported by a particular
ecosystem on a long-term basis
Change in ecosystem-change in
carrying capacity
Exponential Growth



Growth at a
constant rate of
increase per unit of
time
Example:
2,4,8,16,32,64,128
“J curve”
Logistic Growth



Exponential growth until carrying
capacity is reached
Growth then slows or stops
“S” curve