Download Lesson3_PopulationNotes2

Monday, January 23, 2012
• Homework: Short Checkup on
Population Growth on block day.
• Semester test review due Friday
(January 27)
(yes, it counts as a grade)
• Make up missed food web checkup if
missed.
• Make a new logbook entryLimiting Factors and Carrying Capacity1/17/12
Get a sheet in plastic (1 per person) from
the front counter
• Read the information about
carrying capacity and
limiting factors and answer
questions 1, 2, and 3 in
your logbook.
1. Define carrying capacity.
The maximum population of a particular species that
the habitat can support.
The carrying capacity of an ecosystem can change as
environmental conditions change.
2. List two biotic factors and two abiotic factor and
describe how they can be limiting factors.
BIOTIC LIMITING FACTORS– FOOD, PREDATORS,
MATES, BIRTH AND DEATHRATE
**The abundance of or the lack of certain plants then translates into an
abundant or a limited food supply for a chain of other organisms.
** When the population of insects drops, the population of organisms
that feeds on mosquitoes Is affected
ABIOTIC LIMITING FACTORS– LIGHT, SPACE,
WATER, WEATHER, …
**Climate and particular weather conditions can affect the
population size directly by presenting the best conditions for the
growth and reproduction or by presenting conditions that make
growth and reproduction difficult.
**Water is a requirement of all living organisms, and thus it is a
limiting factor
3. Use the terms limiting factors and carrying
capacity to describe the difference between
exponential (J-curve) and logistic (S-curve)
population growth.
3. Use the terms limiting factors and carrying
capacity to describe the difference between
exponential (J-curve) and logistic (S-curve)
population growth.
EXPONENTIAL GROWTH DOESN’T ACCOUNT FOR OR
ISN’T LIMITED BY LIMITING FACTORS. THE POPULATION
INCREASES VERY QUICKLY.
POPULATIONS EVENTUALLY REACH THEIR CARRYING
CAPACITY AS SOME LIMITING FACTOR KEEPS THE
POPULATION FROM GROWING TOO LARGE.
EX. FOOD RUNS OUT, TOO MUCH COMPETITION FOR
FOOD OR MATES, TOO LITTLE SPACE, DISEASE, ETC
Exponential Model of Population Growth
• Population increases rapidly with no limit
• What will a graph look like?
“J” shaped curve
• Rare in nature. Why?
Limit on the amount of resources (food / space)
• unlimitedresources-with plot.html
Logistic Model of Population Growth
When at carrying capacity,
birth rate is equal to
• Accounts for influence
death rate
of limiting factors
• What will the graph
As like?
population reaches
look
carrying capacity,
death rate increases
“S”
WhenStretched
populationout
is small,
birth rate is higher
than death rate
• Populations can’t grow
exponentially forever because of
limiting factors
• Limiting factors can be: biotic–
predators, food, disease,
competition from their own or other
species
• Abiotic– space, water, shelter, soil,
salinity, temperature
• carrying capacity2.html
• Make an entry titledPopulation Growth Notes1/23/12
• It is a “see attached” entry
INCREASE size
• Births
• Immigration
(coming in)
DECREASE size
• Deaths (mortality)
• Emigration
(going out/leaving)
Growth rate =
(births + immigration) – (deaths + emigration)
• If (births + immigration) > (deaths +
emigration), population INCREASES
• If (births + immigration) < (deaths +
emigration), population DECREASES
• If (births + immigration) = (deaths +
emigration), population STAYS SAME SIZE
Sample population graph
B
C
D
Population
A
Time
E
F
G
Interpreting population graphs
Different time periods on the graph are labeled
A-G. Identify which time periods show the
following:
1.
2.
3.
4.
5.
6.
Increasing population
Decreasing population
The highest population
The fastest growth rate
(births + immigration) < (deaths + emigration)
(births + immigration) = (deaths + emigration)
Sample population graph
A
B
C
D
2. Decrease
Population
5. B+I < D+E
Time
E
F
G
Sample population graph
A
B
C
D
Population
6. B+I = D+E
Time
E
F
G
Sample population graph
A
B
C
D
Population
1. Increase
4. Fastest Growth
Time
E
F
G
Sample population graph
A
B
C
D
Population
1. Increase
Time
E
F
G
Sample population graph
A
B
C
D
E
6. B+I = D+E
Population
3. Highest Pop
Time
F
G
Sample population graph
A
B
C
D
E
F
G
2. Decrease
Population
5. B+I < D+E
Time
Sample population graph
B
C
D
E
F
G
6. B+I = D+E
Population
A
Time
1.
2.
3.
4.
5.
C and D show increasing population
A and F show decreasing population
E shows the highest population
C is the fastest growth rate
A and F show
(births + immigration) < (deaths + emigration)
6. B, G and E show
(births + immigration) = (deaths + emigration)
• Changes in Carrying Capacity
• Carrying capacity- the maximum size of a
population that can be supported by an
ecosystem
• The carrying capacity of an ecosystem can
change as environmental conditions change.
• Limiting factors- any factor that controls the
growth of a population
(e.g., food, space, disease, predators)
The graph below shows the growth of a population over time—a
population that has increased and reached a balance due to limiting
factors. (REACHED CARRYING CAPACITY)
Original
population
graph
Population
Time
1) The birth rate DOES NOT change, but the
amount of food and other resources increases
Original
population
graph
Population
Time
2) The birth rate increases but the amount of food
And other resources DOES NOT increase
Original
population
graph
Population
Time
3) A population quickly increases but exceeds the
amount of resources and the population crashes
Original
population
graph
Population
Time