Transcript Population Dynamics and Growth

Population Dynamics and
Growth
Pre AP Biology
Spring ‘12
Competition
• Competition occurs when 2 or more
species use the same resource.
• Examples of the resource are:
– Food
– Light
– Space
– Shelter
– Water
– Nesting sites
Limiting factors
• Limiting factors are the biotic and abiotic
factors in an ecosystem that limits the
existence, numbers or reproduction the
organisms in that environment.
P
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p
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l
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t
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Zone of
Intolerance
Low
stress
optimum conditions
ENVIRONMENTAL FACTOR
stress
zone of
intolerance
High
Limiting Factors
• Examples of limiting factors:
• Temperature: organisms have an optimum
temperature range in which they can survive.
• CO2 levels
• O2 levels
• Humidity
• Amount of sunlight
• Prey availability
• Mineral availability
Kinds of Limiting Factors
1. Density-dependent – has an increasing
effect as population increases. Usually
biotic.
ex: disease, parasites, competition for food
2. Density-independent – has an effect on
all populations regardless of their
population. Usually abiotic.
ex: sunlight, temperature
How Predation Helps
• Predators help keep population size within
the limits of available resources.
Limiting factor graph (example)
• Graph the temperature tolerance for 2
species of plants (aloe vera and ivy). The
data is in sets of three:
A, B, C A = temperature
B = number of aloe vera
C = number of ivy
Use 2 different colors. Remember every
graph needs a title, x and y axis labeled,
and a legend
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0,0,0;
10,0,0;
20,0,2;
30,0,10;
40,2,20;
50,5,40;
60,10,60;
70,12,70;
80,30,60
90,50,30;
100,40,10;
110,20,2
120,5,0
130,0,0
140, 0,0
Data
Population Growth
• Population growth is a change in
population with time
• 3 kinds of growth graphs:
– Linear growth
– Exponential growth
– Logistic growth
Logistic is most common
• Linear growth almost never occurs. It assumes
the exact same rate of growth. (If every 2
people had 3 children…we’d replace ourselves +
1)
• Population growth is sometimes exponential if
resources are unlimited
• Logistic growth is the most common because it
represents exponential growth until resources
limit growth and it levels out.
Carrying capacity
• Carrying capacity – number of organisms
of a population that an environment can
support
2 kinds of strategists or patterns of
population growth:
r-strategists
k-strategists
R-strategists
• Have a rapid period of population growth
• The rapid growth far exceeds carrying
capacity
• Rapid growth followed by a crash
• After the crash there is another period of
rapid growth, etc.
• This organisms have many offspring, don’t
care for their young, and have short life
• Examples: bugs and fish
K-strategists
• Have a long period of slow growth
• Then they reach the carrying capacity.
• At that point they have minor fluxuations in
growth around carrying capacity.
• They have few young, a long life, and tend
to take care of their young.
• Examples: most mammals
Homework
•
Answer the following questions about the
graph.
1. Give the zones of intolerance for aloe vera
and for ivy?
2. What is the optimum temperature for aloe
vera?
3. Which plant grows better outside in South
Texas?
4. How could a person who owns a gardening
store use this information?
Pre AP homework
• 5. Read page 370 and answer question
#2 and #3 on page 370. I expect more
than a sentence answer. Your answers
should fill more than a half a page.