1. Populations Dynamics
As pictures load, instructor can discuss sea otter (almost hunted to extinction by man), killer whale (natural predator of sea otters), kelp (food source for sea urchins), sea urchin (food source for sea otters) balances in the Pacific Northwest, as well as python populations invading the Florida everglades which pose threats to native species, and wolf and grizzly bear populations.

2. Population Dynamics Learning Objectives
What characteristics are used to describe a population?
What factors affect population size?
How is the distribution and abundance of organisms determined by the interactions between organisms and between organisms and the non-living environment?

3. 4 main characteristics of populations
Population Dynamics
4 main characteristics of populations
Geographic range or patterns of distribution
Population density
Age structure
Population size or # of individuals
For Teacher:
Distribute Pre-test “Populations Lesson 1 Pre-test” . This could be done after the first 3 slides are shown, or distribution of pre-test could be done as students enter the room.
To continue after the instructions to take the pre-assessment, CLICK to continue slide content introducing the activity.
After the pre-test collection:
1.Distribute Handout titled, “Organisms in Your Environment”.
2. Questions from the formative questions Handout 2b can be used to assess prior knowledge and guide learning.

4. Geographic Range or patterns of distribution
Information ecologists need to study populations
Geographic Range is the area which is inhabited by a species. Ecologists need to determine the geographic range of a species to study its populations.
For instance bacteria in a rotting log may inhabit only a few square centimeters.
Hydrilla is an aquatic plant native to the warmer regions of Asia. The plant was introduced in Florida and is now an invasive species found in many of our lakes, rivers, and spring systems. In fact, the range of this plant has expanded and it is now found in many places throughout the world and United States.
Links if time permits to show 1) Students how they could research a project and develop a video for enrichment. 2) An educational and informative video about Hyrdrilla verticilla in Florida as a native species.
Student produced video on Hydrilla:
Another link about produced by UF Hydrilla:

5. Geographic Range or patterns of distribution
This map shows the geographic
distribution of killer whales. Killer
whales move from the coast of
California to the Aleutian Islands
During their migrations.
Formative Questions:
1. Do you think the geographic distribution of bacteria would be the same as the geographic distribution of the killer whales?

6. Geographic Distribution Maps of Pythons invading Florida help scientists learn about their populations.

7. Population Density Information ecologists need to study populations
2. Population Density: The number of individuals of a population in a given area. Population density is the number of individuals in a measurable region.
The members of the population can be spread out or can be clustered throughout the area. Population densities can be small or large.
If there are no limiting factors, population densities can be larger than if limiting factors are present. Limiting factors are things like lack of resources, predators, natural disasters and lack of space.

8. Population Density Population Density Equation
Population Density = # of individuals/given area
This saguaro cactus in a desert community has a low density.

9. There are 4 main characteristics of Populations
Geographic Distribution or Range √
Population Density √
Now we will look at two more characteristics
Age Structure
Population Growth Rate

10. Age Structure
Age Structure: Age structure diagrams are useful in predicting future population growth rates. Population profiles graph the numbers of individuals in different age groups within a population.
Overview, age structure should be explored further in later lessons, or if time allows teacher can elaborate on how they are useful.
If there are higher numbers of teens, the population will increase in future years!

11. Population Size or # of individual Population Growth Rate
Populations can remain constant over time.
Population can increase rapidly over time.
Examples: (1) the Pacific Sea Otters once protected from hunting
(2) the Burmese Pythons in Florida
Populations growth can also see a decrease in size
Example: (1) otter populations can due to predation by killer whales.
(2) Native populations can decrease due to invasive species.

12. The question arises, how do these types of interacting factors shape and influence population growth?
Three Factors Can Affect Population Size
1. The Number of Births
A population will grow if the births out number the deaths
2. The Number of Deaths
A population will shrink if the deaths out number births

13. Population Growth Rate
3. The Number of Individuals that Enter (Immigration) or that Leave (Emigration) the Population
Immigration: The movement of individuals into an area,
which can cause an increase in the population size.
Emigration: The movement of individuals out of an area,
which can cause a decrease in the population size.
*Population size will not change and will remain fairly constant, if the birth rate is the same as the death rate AND immigration is the same as emigration.

14. Some Causes of Immigration and Emigration
Maturity of young = they leave their birth area to seek mates and immigrate to new areas to establish a territory. Wolves and bears are some examples.
Destruction of habitat = (for example building of a housing development) can cause animals to emigrate from an area and immigrate into an area with intact habitat
Food shortages = they will leave an area and go out searching for food.
Natural disaster = can affect both immigration and emigration rates, as well other limiting factors.

15. How do we measure growth?
Exponential Growth happens when the individuals in the population reproduce at a constant rate. At first the number of individuals in a growing population increases slowly, but over time the population grows infinitely large. If a population has abundant space and food, and is protected from disease, predators, and natural disasters, the organisms in the population will multiply and increase, thus under ideal conditions, with unlimited resources, a population will grow exponentially.

16. Exponential Growth Rate Examples….
Lesson 3
Notice the J Shaped Curve

17. Factors that may cause population growth to slow down.
Logistic Growth
Logistic Growth happens when a population’s growth decreases or ceases following a period of exponential growth.
Imagine a few animals are introduced to a new area plentiful in resources, the growth rate would increase exponentially, but as resources become less available, the growth of a population slows or stops.
Factors that may cause population growth to slow down.
Birthrate decreases, or deathrate increases, or both events occur at the same rate. Immigration rates decrease and the rate of emigration increases, or both.
Lesson 3

18. Logistic Growth continued…
Logistic Growth continued…. Most normal populations follow a logistic growth curve.
Note that even when the population growth is said to stop, the population is still slightly fluctuating.
Growth levels off as a population reaches what is called the carrying capacity.
The carrying capacity represents the largest number of individuals that a given environment can support.
Logistic Growth
Carrying Capacity
Lesson 3
Be sure to address misconceptions: The population may not start at zero. There are 3 phases to logistic growth, not just 2 phases. Growth steadily increases (phase 1) growing exponentially, and THEN slows (phase 2), and levels off when carrying capacity is reached, (phase 3).
Note the S shaped curve for Logistic Growth

19. Review of Exponential & Logistic Growth
Lesson 3
(Click on either picture to use an applet simulation of exponential or logistic growth.)

20. Carrying Capacity
When the birthrate and the death rate are the same, and when immigration equals emigration, population growth stops.
Carrying capacity is the maximum number of individuals of a particular species that a particular environment can support.
Once a population reaches the carrying capacity of its environment, a variety of factors act to stabilize it at that size. .

21. It’s your turn to Analyze the Data
Table 1
Days
# of Fruit Flies 5 10
100 15
200 20
400 25
600 30
620 35
640 40
Make a graph utilizing the data in each table. Table 1 will be used to show the growth rate of a fruit fly population. The other graph will utilize data from Table 2 on the next slide to show the growth rate of a populations of rabbits.
Make sure to title your graphs and label the x-axis and the y-axis.
Lesson 3
Students can use empty charts on Power Point Notes to label and plot data.

22. Analyzing Data continued….
Table 2
Generations
# of Rabbits 1
100 2
105 25
1000 37
1600 55
2400 72
3350 86
8000
13,150
2. What type of growth do you find in the fruit fly population? Is it the same type of growth seen in the rabbit population?
3. Is there a carrying capacity on either graph, and if so, when does the population reach it? What is the maximum number of individuals supported at this time?
4. What would happen, if during the rabbits’ 20th generation, predators moved into the rabbits’ habitat and began eating rabbits?
Lesson 3

23. Here they are again… The 4 main characteristics of Populations
Geographic Distribution or Range
Population Density
Population Growth Rate
Age Structure

24. Review of Key Terms Population Density:
The number of individuals in a given area
Immigration:
The movement of individuals into an area
Emigration:
The movement of individuals out of an area
Exponential Growth:
With unlimited resources, growth can be infinite
Logistic Growth:
Rapid growth followed by growth slowing down
Carrying Capacity:
The maximum number an environment can support

25. The End References Biology by Miller & Levine, Prentice Hall, 2002 Guided Reading and Study Workbook, Images from various sources using Google Images doing a search on public domain and royalty free images