Transcript Populations – Chapter 5

Populations – Chapter 5
Population - A
group of
organisms that
belong to the
same species
and living within a
certain area
Vocabulary Terms
• Population Density – Number of
individuals per unit of area
• Population Growth – Increase in the size
of the group
• Biotic Potential – Highest rate of
production possible under ideal conditions
ZPG
• When a population stays the same it is
said that there is zero population growth.
• What factors go into determining a growth
rate?
Determining a Growth Rate
1. Movement out of the area - Emigration
Movement into the area – Immigration
2. Number of organisms born – Birth Rate
Number of organisms that die – Death
Rate
For ZPG to occur:
• Birthrate + Immigration = Death Rate and
Emigration
Populations are
Changing!!
Exponential and Logistic Growth Patterns
Trend #1: Exponential Growth
• J-Shaped Curve
• Ideal environmental
conditions
• There are no limiting
factors holding this
population back!! Ex) lots
of food and water and
space
• Population reproduce at a
constant rate
Trend #2: Logistic Growth
• S-Shaped Curve
• Logical Growth
• Limits on population
size based on
resources, Limiting
Factors, are present
An area can only maintain so much
and remain stable.
• Found only in
logistic
growth.
• Means the
number of
organisms an
ecosystem
can maintain
over time
Carrying
Capacity
What happens if the population
goes over carrying capacity?
• The population crashes
Graphing Population Trends
• Now: Create a graph of the chipmunk
population from 1940 to 1995.
• Remember to label the x and y axis.
• Time always goes on the _______!!
• Give it a title!
Realistic Growth
• In the real world there are limiting factors
that eventually come into play as a
population gets larger.
• The are called limiting factors because
they limit the growth rate of a population.
• This limit causes the population growth to
level off, meaning that the population will
reach carrying capacity.
Carrying Capacity
Factors which cause carrying
capacity
• Density Dependent: Do not affect all
populations the same.
Ex) Food, Space, Mates, Disease,
Predation
• Density Independent: Affect all
populations the same despite population
size.
Ex) Natural Disaster (Flood,
Drought, Fire), Pesticides or
Poisons, Destruction of Habitat
Rabbit Island
• Scenario 1: Small Island of 5 Rabbits
Climate Food supply Predation • Scenario 2: Small Island of 500 Rabbits
Climate –
Food Supply –
Predation -
Summary of Scenario
• Which ones changed based on the
population size?
Food Supply and Predation (These are
Density Dependent)
• Which ones stayed the same?
Climate (This is density independent)
Summary Questions
• How do you explain the exponential
growth pattern in the beginning…what
factors affected this growth?
• How do you explain the then drastic
decline?