**Instructions fill in notes WHILE you read the chapter. Add any additional notes during class.
***Notes that you are to complete before lecture will be preceded by the following symbol:

Part 7: POPULATIONS
Review
[Chapter 4 Pages 95- 103]

Remember that the definition of a population is a particular species living
in a particular place at the same time.
 Which is the correct example of a population?
a. 200 ants
b. 200 ants living in the front flower bed outside the 600 bldg of Duluth High
School
c. 200 fire ants living in the front flower bed outside the 600 bldg of Duluth
High School
Population Growth:
Populations fluctuate (change) in response to the environment. Under optimum (ideal)
conditions a population will reach its biotic potential (highest rate of reproduction).
 Use the term Biotic Potential in sentence that illustrates the meaning of the word.
EXAMPLE: Let’s start with 2 fruit flies – 1 male and 1 female. A female fly can
produce about 120 eggs at a time. Assume the offspring are 50% male and 50%
female in each generation. Let’s follow the offspring and also assume that ALL
offspring survive.
Generation
# of Offspring
1
120
2
3
4
5
6
7
Each generation only lasts for a few weeks. Even so, lucky for us the biotic
potential is not reached in real fly life, because many of the offspring do not
survive. However, populations do approach biotic potential. If we plot the above
population growth on a graph, we get the following curve:
Number of flies
Fly Generations
*The graph looks like the shape of what letter?
We call this type of curve a ___ - shaped curve and the population growth it
represents ______________ _____________.
Population Growth Continued:
Populations do not grow indefinitely! Population size and growth may be limited by
factors called limiting factors. Limiting factors, such as food and space, cause a
population to stop increasing.
 Examples of other limiting factors that may limit population growth:
The leveling-off of population growth due to limiting factors results in an S-shaped
growth curve.
 On the graph below draw in an “S-shaped” curve:
Number of
Individuals in
Population
Time
When population growth levels-off due to limiting factors, we say the population has reached its carrying capacity.
 Define Carrying Capacity
 Draw the carrying capacity on your S-shaped curve as a dotted line
Review Population Growth Graphs
*Populations Grow when births exceed deaths (also by immigration) and populations Decline when
deaths exceed births (also by emigration).
 Define Natality:
 Define Mortality:
 Define Immigration:
 Define Emigration:
*J-shaped Population Growth Curve
The J-shaped curve shows exponential growth at a constant growth rate that is not limited by
limiting factors.
*S-shaped Population Growth Curve
The S-shaped curve shows exponential growth of a population at a constant growth that is
eventually limited by environmental factors.
NOTE: Populations sometimes grow above the carrying capacity until deaths exceed
births and the population size decreases below the carrying capacity, only to once again
increase to reach or exceed the carrying capacity. That is the population fluctuates once it
reaches the carrying capacity. The number of organisms tends to rise above and below
the carrying capacity.
 Draw an S-shaped curve that depicts the fluctuation of a population once it
has reached its carrying capacity.
Limiting Factors:
 Define Limiting Factor (pg. 68):
There are two types of limiting factors that affect population growth:
1. Density Dependent
2. Density Independent
1. Density Dependent limiting factors: Factors which have a greater effect as the
population increases. That is, these limiting factors depend on the density or size
of the population.
 Give examples of density dependent limiting factors:
2. Density Independent Limiting Factors: Factors that affect all populations regardless
of their density or size.
 Give examples of density independent limiting factors:
-
Life-History Patterns:
The most important factor that determines population growth is reproduction. The
reproductive pattern of an organism is called its life-history pattern.
There are two basic types of life-history patterns that determine the growth of an
organism’s population.
1. Rapid Life-History patterns
2. Slow Life-History patterns
1. Characteristics of organisms with Rapid Life-History Patterns:
Populations of theses organisms increase rapidly, then decline rapidly as
environmental conditions suddenly change and become unsuitable. The small
surviving population will begin reproducing exponentially when conditions are
again favorable. Thus, organisms with rapid-life history patterns are successful
in environments that are unpredictable and change rapidly.
2. Characteristics of organisms with Slow Life-History Patterns:
 Population Growth Practice:
Bacteria reproduce by splitting (binary fission). A certain species reproduces
every 20 minutes. If we start with one bacterial cell, how many cells will there be
at the end of 6 hours? Show your work and explain how you derived your
answer.