Pre-Lab: The Growth Cycle of Yeast
Problem What type of population growth occurs in a yeast culture?
Materials yeast culture, stirring rod, dropper pipettes, microscope slides, coverslips, microscope, 10-mL graduated cylinder, test tubes, test-tube rack, graph paper
Lab Manual Chapter 5 Lab
Skills Measure, Calculate, Interpret Graphs
Connect to the Populations depend on, and are limited by, their environments. A population can grow when its members have the resources they need to survive and reproduce. Factors that can limit those resources include natural disasters, such as forest fires, and competition from other species. Predation and disease are also limiting factors for populations.
In nature, populations often experience cycles of growth and decline. In this lab, you will investigate whether such a cycle occurs in yeast populations.
Review What is the carrying capacity of a population?
Sequence Briefly describe the three phases of logistic growth.
Relate Cause and Effect Describe two different ways that a population might achieve a growth rate of zero.
Classify After two weeks of hot and sunny days with very little rain, the blades of grass in a backyard began to wither and die. Were any of the factors that caused the decline of the grass population dependent on density? Explain.
Preview the procedure in the lab manual.
Infer Why was grape juice used to prepare the yeast cultures instead of plain water?
Form a Hypothesis Why will you locate the yeast cells under low power, but switch to high power to count the cells?
Calculate Suppose you have to do one dilution of your culture before you are able to count the yeast cells. If you count 21 yeast cells in the diluted sample, how many yeast cells were in the same area of the undiluted sample?
Predict What do you think will happen to a yeast population between Day 3 and Day 7? Give reasons for your answer.
Visit Chapter 5 online to test yourself on chapter content and to find activities to help you learn.
Untamed Science Join the Untamed Science crew as they learn the latest techniques for counting populations.
Art in Motion View a short animation that brings age-structure diagrams to life.
Art Review Review your understanding of limiting factors with this drag-and-drop activity.
InterActive Art Manipulate factors such as starting population size, birthrate, and death rate to see how they would impact moose and wolf populations over time.
Data Analysis Analyze logistic growth curves in order to make predictions about zebra mussel growth.