Transcript Chapter 5 Notes

Populations
Interdependence in Nature
Chapter 5
Describing Populations
• Group of organisms of a single species
that lives in a given area
• Studied by
– Geographic range
– Density and distribution
– Growth rate
– Age structure
Describing Populations
• Geographic range
– The area inhabited by a
population (where they live)
– Native (natural) range vs.
introduced range
• Hydrilla
• Zebra mussels
• Density and distribution
– Number of individuals per
unit area
– Three general types
• Random
• Uniform
• clumped
Describing Populations
• Growth Rate
– Determines whether
the size of a
population increases,
decreases or stays the
same
• Age structure
– The number of males
and females of each
age a population
contains
Population Growth
• Birthrate vs. death rate
– Higher birthrate – population grows
– Higher death rate – population shrinks
– Equal rates – zero growth
• Immigration vs. emigration
– Imm- growth caused by moving in from
elsewhere
– Em- decline caused by leaving a population
range
Types of Growth
• Exponential Growth
– The larger a population, the
faster it grows
– Under ideal conditions with
unlimited resources,
populations will grown
exponentially
– Causes a J-shaped curve
when graphed
• Logistic Growth
– Phases of growth
• Exponential
• Growth slows
• Growth stops
– Causes an S-shaped when
graphed
– Carrying capacity – the
maximum number of
individuals of a particular
species a particular
environment can support
Limits to Growth
• Limiting factors –
controls the growth of
a population
– Determine the carrying
capacity of an
environment
Two types of limiting factors
• Density-dependent
–
–
–
–
–
–
Competition
Predation
Herbivory
Parasitism
Disease
Stress from
overcrowding
• Density-independent
– Unusual weather
– Natural disaster
Human Population Growth
• Tends to increase
– Rate of increase has changed over time
– Causes of increase – advance of civilization
Patterns of Human Population
Growth
• Demography – study of human
populations
– Looks at the characteristics of human
population
– Tries to explain how populations will change
over time