INVESTIGATION 9.2
Asexual reproduction in yeast and
amoeba
STUDENT LABORATORY NOTES
Introduction
Asexual reproduction is the creation of offspring identical to the parent plant. This enables organisms
to repopulate areas rapidly when conditions are favourable. Yeast are an example of an organism that
can reproduce asexually, via the production of buds that break off from the parent organism. These
buds are smaller than the parental organism.
An amoeba is another example of an organism that can reproduce asexually, via the process of binary
fission. The daughter cells are similar in size to that of the parental cells.
Aim
To observe budding in yeast and binary fission in amoeba under the microscope
Hypothesis
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Preparation for task
Location to conduct this task
In a laboratory
Duration
40–60 minutes
Group size
2–4 students
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Topic 9 | Reproductive strategies
Methodology
Materials (per group)
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500 mL beaker
125 mL warm water (41 °C –46 °C)
Dry yeast sachet (7 g)
5 g sugar
250 mL measuring cylinder
Microscope slide with cavity and coverslip
Thermometer
Microscope
Pipettes
Sugar
Electronic scales
Stirring rod
Prepared slides of amoebae dividing
To share with the class
 Kettle to warm water to 40 °C
 Water baths
Health and safety guidelines
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Yeast must be disposed of as a biohazard material.
Microscope slides can cause cuts — handle carefully.
Do not ingest any materials.
Method
Part A: Observing budding in yeast
1. Measure and pour 125 mL of 40 °C water into a beaker.
2. Add 5 g of sugar and the yeast sachet.
3. With a stirring rod, stir until the yeast is dissolved.
4. With a pipette, add three drops of the yeast solution to a microscope and add a cover slip.
5. Store the yeast suspension in a 40 °C water bath.
6. View under the microscope and sketch a diagram of your observations.
7. Count and record the number of budding yeast cells that can be seen.
8. Repeat every 10 minutes for 30 minutes.
Part B: Observing binary fission in amoebae
1. Observe prepared slides of amoebae dividing under ×100 and ×400 magnification.
2. Draw a sketch of your observations in the results at ×400, showing different stages of
division.
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Topic 9 | Reproductive strategies
Results
Complete the following results tables for each component.
TABLE 1 Budding in yeast
Time
Yeast suspension diagram
0 mins
10 mins
20 mins
30 mins
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Topic 9 | Reproductive strategies
TABLE 2 Division of amoeba
Diagram
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Topic 9 | Reproductive strategies
Discussion questions
1. Both yeast and amoebae reproduce asexually. Compare the modes of asexual reproduction for
these two organisms.
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2. What advantage does asexual reproduction confer?
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3. Identify a disadvantage of asexual reproduction and how this impacts on the survival of a
species.
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4. In step 7 of part A, you were asked to count the number of budding yeast cells. What type of
error would you expect to occur, and how could this be overcome if this practical was to be
repeated?
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5. Design an experiment to test the effect of temperature on the rate of asexual reproduction in
yeast.
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Topic 9 | Reproductive strategies
Conclusion
Write a conclusion for this investigation.
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