Algae and Brine Shrimp Populations
Warm up
 What is a limiting factor?
 Give some examples.
 Any biotic or abiotic factor that acts in some way to limit
the number of individuals that survive and reproduce in
a population.
 Temperature
 Size of habitat, ecosystem
 Predators….Nom, nom, nom…..!!
Review Mono Lake
 In Mono Lake we have:
 Producers: Algae
 First level consumers: Brine flies and shrimp
 Second level consumers: birds
 Third level: Coyotes
 The field ecologists who study Mono Lake have noted that
the populations vary a lot over the course of a year.
 For example: At times there are almost no brine shrimp and
at others there are trillions.
 They reasoned that there must be some limiting factors at
different times of the year.
Review Mono Lake
 The survival of the whole ecosystem depends on the
algae.
 If the algae population is large, the ecosystem will be
able to support a lot of primary consumers.
 Scientists wanted to understand the factors that limit
the populations of two important organisms in the
lake, the planktonic algae and the brine shrimp.
 We will look at the set up and data from their year long
experiment.
Experiments
 Look at lab pages 34 and 35. They describe the set up and
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procedures.
Eight aquariums were set up and maintained as described on
page 34.
Each aquarium had only one variable that changed. (In a
controlled experiment we can only change ONE variable!)
The populations were sampled every month for one whole year.
Look at the data that was collected and recorded on page 36.
After looking over the experiment and data on pages 34, 35 and
36, answer the questions on page 37. Use complete sentences and
give QUALITY conclusions with DATA from the experiment to
support them.
Things to think about
 Which experiments maintained cold temps all year?
 Which experiments maintained warm temps all year?
 Which had the same temps as Mono Lake all year?
 What would a graph of time versus temps look like for
the aquariums that had the same temps as Mono Lake
through out the year?
 The water temps would increase in the summer months.
Discuss Analysis
 Don’t forget a limiting factor is any biotic or abiotic
factor that acts in some way to limit the number of
individuals that survive and reproduce in a population.
 What effects did you find light and temperature had
on Mono Lake and the ecosystem?
 Within the light and temperature ranges that were
studied, algae were not significantly limited.
 Population increase was slightly slower in the low light
situation, but at the end of the year, the algae
populations were the same in all four aquariums.
Analysis cont.
 Brine shrimp were not limited by light intensity, but
were significantly limited by temperature.
 In the low temperature situation, none of the eggs
hatched.
 In the variable-light situation the population growth
and decline were directly related to water temp. The
greatest population increase was in the warm water.
Other Factors
 The Mono Lake populations would potentially be
subjected to other limiting factors.
 Algae could be impacted by abiotic factors like carbon
dioxide, nutrients and space. Biotic factors could be
predation by primary consumers and disease.
 Brine shrimp could be impacted by abiotic factors like
oxygen and space and biotic factors like food,
predation by secondary consumers and disease.
 Read Limiting Factors.
Wrap Up
 Read Limiting Factors. Pages 22-24.
 Define in your journals the following:
 Reproduction
 Reproductive potential
 Limiting factors
 Carrying capacity