Download POPULATION DYNAMICS

Bell Ringer
1. Why is the population changing so drastically?
2. What factors are affecting the change?
3. Will the population continue to grow indefinitely?
WORLD CLOCK
10 minutes
Objectives
• Students will use data and information about
population dynamics, abiotic factors, and/or biotic
factors to explain and/or analyze a change in
carrying capacity and its effect on population size in
an ecosystem.
http://video.nationalgeographic.com/video/news/7-billion/ngm-7billion
After watching this video, stop and jot the
following questions:
1. Does over population concern you?
2. What would zero population growth look like?
3. How could we design a society that can sustain
itself at zero population growth?
1. How does a population increase?
2. How does a population decrease?
3. What are possible consequences of a constantly
increasing population?
Change in
Population
=
Exponential Growth
• Exponential growth
occurs when the
individuals in a
population reproduce
at a constant rate.
• Under ideal conditions
with unlimited
resources, a population
will grow exponentially.
Logistic Growth
• As resources become
less available, the
growth of a population
slows down or stops.
• Logistic growth occurs
when a population’s
growth slows or stops
after a period of
exponential growth.
Which graph is indicative of natural growth within a population?
Can you think of an example of exponential growth? Logistic growth?
Boom then stable
Boom and Bust
1. Where do you see exponential growth in the world?
2. Where might you see logistic growth?
Can you think of some resources that could limit population growth?
Characterize these resources as abiotic or biotic?
largest number of
individuals a given
environment can
support.
Limiting Resources
Population size (N)
Carrying
capacity is the
Carrying capacity (K)
What does each part of the graph mean?
Exponential
growth
Time (t)
Exponential and Logistic Population
Growth: J-Curves and S-Curves
• As a population
levels off, it often
fluctuates slightly
above and below
the carrying
capacity.
Limits to Growth
• Limiting factor: a factor that causes population
growth to decrease.
• Density-dependent factors are limiting factors
that depend on population size. (usually due to
biotic)
• Competition
• Intraspecific
• interspecific
• Predation
• Parasitism
• Disease
• Food
• Shelter
• Water
• Space
Predator – Prey Relationship
Darwin
Lied
Density-Independent Limiting Factors
• Affect a population no matter what its size is
(usually abiotic)
• Unusual weather
• Drought
• Floods
• Natural disasters
• Seasonal cycles
• Certain human activities
• Damming rivers
• Clear-cutting forests
• Forest Fires
Wolf and Moose Populations on Isle Royale
Harsh Winter
60
2400
Parvovirus arrives
50
2000
400
40
1600
30
1200
20
800
10
0
1955
400
Harsh Winters
0
1960
1965
1970
1975
Moose
1980
Wolves
1985
1990
1995
Human Population Growth
• Until about 500 years ago, the world’s human
population remained fairly stable.
• Then, as advances in medicine, agriculture, and
technology occurred, the human population
began growing
very rapidly.
Industrial
Revolution
• Today the world’s
Today,
the
begins
Agriculture
begins
Bubonic
human population
plague
Plowing
and
is greater than 7
irrigation
billion people, and
it continues to
grow, but at a
slower rate.
Think-Pair-Share
• Are humans susceptible to the kind of resource
shortages that affect the populations of the other
species?
• What might the ideal graph for humans look like over
the next 200 years?
Which of the populations show seasonal
fluctuations? (The rabbit, fox, and warbler.)
1. What do you think is causing the Warbler populations to shrink?
2. How do you think the populations of the rabbits and the foxes are
related?
Accountability Talk
•
•
•
•
•
You have 5 min to respond to your question
Then rotate
You have 1 min to read
You have 5 min to respond
Repeat until the same person gets their
paper back (3 more rotations)
• Do you agree with your original statement?
5 minutes
1 minute
5 minutes
White Board Attack!!!!
1. When brown tree snakes were first introduced to the
island of Guam, they had no natural predators. These
snakes ate many of the eggs of insect-eating birds.
What probably occurred after the introduction of the
brown tree snakes?
A. The bird population increased.
B. The insect population increased.
C. The bird population began to seek a new food
source.
D. The insect population began to seek a new food
source.
2. A population of organisms grows briefly and then
stabilizes. What does the leveling off of the population
size indicates?
A. The population has reached the carrying capacity of
the ecosystem
B. The population has exceeded the carrying capacity
of the ecosystem
C. The population is affected by a densityindependent limiting factor
D. The population is no longer able to adapt to
environmental changes
3. The number of pythons found throughout
Everglades National Park has increased in recent
years. These huge snakes are not native to Florida
and are believed to have been released into the wild
by pet owners. Wildlife biologists have initiated
attempts to capture and remove these pythons.
Which statement best explains the biologists’ reason
for removing these pythons from the Everglades?
A. The pythons could upset the territorial
boundaries of native organisms.
B. The pythons could adapt to overcome diseases
common to native snakes.
C. The pythons could prey on native organisms and
cause native populations to decline.
D. The pythons could begin to interbreed with native
snakes and produce a more successful species.
4. Which of the following is an example of primary
succession?
A. lichens growing on rocks following a volcanic
eruption
B. grasses growing after a forest fire
C. oak trees replacing pine trees in a forest
D. non-native species introduced into a climax
community
5. Draw a graph (with no units or numbers) that
clearly labels exponential growth, logistical growth
and carrying capacity.
Exit Slip
5 minutes
Home Learning
• Students will review and use vocabulary terms
learned in today’s lesson for a minimum of 4
sentences, to describe how they observe changes
the ecosystems where they live.