rabbits can very quickly eat all the vegetation in a grassland ecosystem. With the vegetation gone, food becomes the limiting factor and the rabbits may starve or move to another area (immigration). The grassland now has a reduced carrying capacity for rabbits until the vegetation grows back again.
Increasing or decreasing the limiting factors in an ecosystem will result in an increase or
decrease in populations. Some of the limiting factors that are explored in this lesson include food, water, shelter, mates, too many males, too many females, drought, fire, hunters, car traffic, immigration, emigration, predators, dangerous organisms, parasites, and disease.

Engage

How is population size affected by different environmental factors? Give 2 and explain how it affects population size.




Here we see population graphs of two different populations of deer. 


What do you think could account for the differences between the two populations of the deer?


What do deer need to survive?


What interferes with a deer’s survival?




Explore

You will be conducting your own population study with a population size of 100 deer. You will be exposing your deer to factors that they commonly encounter in their natural ecosystems and will be evaluating how it impacts their population.

Directions:
Draw one card out of the envelope at a time.
Read what the card says and record the results in your data table. 
Make a copy of this data table to input your results. It will also generate a graph based on your results.
Example of how to fill in the data table is here:

DO NOT put the card back in the envelope.
Draw the next card and continue drawing and recording data until you have drawn 20 cards and completed all 20 trials.
When you are finished with your trials, put all cards back in the envelope.

When completed with all 20 rounds, copy and paste your graph here:




Explain

Give an overall description of your graph/data. 


Explain what factors accounted for the major increases in your population.


Explain what factors accounted for the major decreases in your population.


Based on the cards that you chose, and using your data table as a reference, what do you think a “limiting factor” is?


What were some of the biotic limiting factors in the deer’s ecosystem?


What were some of the abiotic limiting factors in the deer’s ecosystem?


Carrying capacity is the maximum number of organisms that an ecosystem can support. Looking at your data table and graph, what would you predict is the carrying capacity for your ecosystem? Explain your choice.


What is the relationship between limiting factors and carrying capacity in an ecosystem?


Predict what you think would happen to a population that exceeds the carrying capacity for its ecosystem.


Explain how an immigration (movement INTO an area) of deer would impact the population in terms of numbers, limiting factors, and carrying capacity.


Explain how an emigration (movement OUT of an area) of deer would impact the population in terms of numbers, limiting factors and carrying capacity.




Evaluate
Directions: Highlight the correct answer and explain why it is the best answer for the question.
Question (highlight the correct answer)
Explanation
The carrying capacity of an ecosystem is the maximum number of individuals of a particular species that can be supported on a long-term basis in a given amount of land.  For example, the carrying capacity of the Florida Panther may be 50 panthers per 10,000 square kilometers of habitat in the Everglades ecosystem.  Which of the following determines the carrying capacity of an ecosystem?

the availability of resources required for survival 
the average daily temperature of the ecosystem	
the number of predators found in the ecosystem 
the amount of disease affecting organisms in the ecosystem


The graph shown represents the population growth curves of two different species of organisms, A and B. 

What is a valid prediction based on this graph?

Species A will eliminate species B after 1 year.
Species A will not be present in the winter months.
Species B will attain maximum population size each autumn due to a decrease in temperature.
Species B will decrease in population size approximately 2 months after a decrease in the population size of species A.


The food web below shows the relationship between different factors in a forest ecosystem.

Identify an abiotic limiting factor that could inhibit the growth of the snake population. 
disease in the grass
a decrease in air and soil quality
an increase in the hawk population
a decrease in the number of grasshoppers


Goatfish are fish that move in schools and feed on plankton and plant matter.  Natural predators of the goatfish include sea trout, sharks, pelicans and dolphins.  The graph below shows how the number of goatfish in an area has changed over time.

Based on the data, one student concludes that a new predator was introduced into the area during this time period.  Which of the following is a likely alternate explanation for the change in the goatfish population?

the temperature of the area increased	
the amount of goatfish prey increased in the area
the amount of aquatic plants in the area decreased 
the amount of goatfish parasites decreased in the area


The graph below shows changes in the sizes of four animal populations over a 16-year period.  

In which population was the birth rate most likely greater than the death rate from year 8 to year 12? 
population 1		
population 2		
population 3		
population 4