Vernier Software and Technology
Vernier Software & Technology

Population Dynamics


As organisms reproduce, die, and move in and out of an area, their populations fluctuate. In a closed population, organisms do not move in and out of an area, so their populations change only through natality, or births, and mortality, or deaths of individuals. Yeast are very small, rapidly reproducing organisms. They can experience dramatic population changes over a relatively short time. In this experiment, a population of yeast will be given a small amount of food and placed in a closed environment. Organic materials will not enter or leave the environment—only inorganic gases will be allowed to be exchanged. The population of yeast can be monitored by measuring the turbidity, or cloudiness, of the medium that contains the yeast.

To measure the yeast population, you will be using the Colorimeter or Spectrometer. In this device, light from an LED light source will pass through the medium containing yeast and strike a photocell. Photons of light that strike a yeast cell will be reflected away from the photocell and will make the medium appear more turbid. The Colorimeter or Spectrometer monitors the light received by the photocell as either an absorbance or a percent transmittance value. The absorbance value is proportional the population of yeast present in the medium.


In this experiment, you will

  • Use a Colorimeter to monitor a closed population of yeast.
  • Use a microscope to monitor a closed population of yeast.
  • Compare the population estimates obtained using the two different techniques.
  • Practice making dilutions for population counts.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Option 3

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Biology with Vernier »

Biology with Vernier

See other experiments from the lab book.

1Energy in Food
2Limitations on Cell Size: Surface Area to Volume
3Acids and Bases
4Diffusion through Membranes
5Conducting Solutions
6AEnzyme Action: Testing Catalase Activity
6BEnzyme Action: Testing Catalase Activity
8The Effect of Alcohol on Biological Membranes
9Biological Membranes
11ACell Respiration (O2)
11BCell Respiration (CO2)
11CCell Respiration (Pressure)
11DCell Respiration (CO2 and O2)
12ARespiration of Sugars by Yeast
12BSugar Fermentation
13Population Dynamics
14Interdependence of Plants and Animals
15Biodiversity and Ecosystems
16AEffect of Temperature on Respiration
16BEffect of Temperature on Fermentation
17Aerobic Respiration
18Acid Rain
19Dissolved Oxygen in Water
20Watershed Testing
21Physical Profile of a Lake
23AEffect of Temperature on Cold-Blooded Organisms
23BEffect of Temperature on Cold-Blooded Organisms
24ALactase Action
24BLactase Action
25Primary Productivity
26Control of Human Respiration
27Heart Rate and Physical Fitness
28Monitoring EKG
29Ventilation and Heart Rate
30Oxygen Gas and Human Respiration
31APhotosynthesis and Respiration (O2)
31BPhotosynthesis and Respiration (CO2)
31CPhotosynthesis and Respiration (CO2 and O2)

Experiment 13 from Biology with Vernier Lab Book

<em>Biology with Vernier</em> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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