Yakima WATERS Mini Lesson
Freeze Tolerance in Frogs: Making Frogsicles
Targets and Assessment
WA Science Standards Addressed:
 9-12 INQB Investigate
 9-11 ES2D
 9-11 LS1A
 9-11 LS2A
Lesson Parameters
Content Area: Biology
Assessments:
 Rubric
Suggested Time: 90 minutes
Overview: Observe a rare process in which frogs become
completely frozen and thawed back to life
Grade Level: 9-12
Special Materials:
Freeze tolerant frogs (Wood frog, pacific chorus frog, or
spring peeper), cooling bath, ice nucleator, and ethanol)
Learning Outcomes:
Knowledge: Students will be able to state the physiological processes which are required to survive freezing and
subsequent thawing, and why it is so unusual in vertebrates. Students should be able to describe which factors allow for
freeze tolerance and which factors lead to freeze avoidance. Students should also be able to explain why humans are
currently unable to survive freezing.
Skill: Students should be able to generate a research question based on prior knowledge, create a testable
hypothesis, and make predictions.
Science Concept Background:
Freeze tolerant organisms must undergo a series of changes as their temperatures decrease to protect cells, tissues,
and organs from damage due to ice in order to survive freezing. In frogs, glucose synthesized and mobilized to vital
tissue and organs to provide an energy source for anaerobic cellular respiration. Cellular fluids need to be moved to
intercellular space to prevent damage to the cellular membranes. Freeze tolerance is an effective way to suppress
metabolism in the winter when food is scarce and sunlight is reduced.
Materials:
A Cooling bath capable of temperatures down to a minimum of 30 degrees Celsius
Ethanol
Frogs – Wood frog (Rana sylvatica), pacific chorus frog (Pseudacris regilla), or spring peepers
(Pseudacris
crucifer) – have enough individuals to present at least two samples in several different stages of freezing, thawing, and
normal
An ice nucleator – this is necessary to begin the formation of ice crystals within the frog, otherwise it
would
supercool and unlikely survive
Procedure:
-Freeze at least four frogs two days before the lab. Begin thawing two individuals the night before the lab
-Place the frogs in a test tube into the cooling bath set at -30 degrees Celsius. When the temperature reaches -10
degrees Celsius spray the test tubes with the ice nucleator to induce crystallization in the frogs
-Students should answer prelab questions
-Ask them to generate questions to test, such as “what issues must be accounted for to survive being frozen?”
-Ask students to generate a testable hypothesis
-Connect the concept and procedures to the students’ hypotheses
-Students should answer post lab questions and report results
Key questions:
-What happens to body fluids when their temperature drops below its freezing point?
-Are frozen frogs alive?
-What qualifies as being “alive”?
Author: Jack Lester, Yakima WATERS Project, CWU, 2009-2010
-What processes are significantly reduced or stopped all together?
-How is it possible for frogs to survive freezing, but not humans?
-Which treatments did you test?
-Sometimes the frogs do not survive this treatment. Why is it some survive and some do not?
-How does climate change affect organisms that are adapted to freezing in the winter? Will they have enough
food to survive the winter if they don’t freeze?
Teaching Tips:
Connect the concepts of homeostasis, adaptation, and winter energetics.
Supplements:
Students should already have been exposed to text and lectures about homeostasis, evolution, and metabolism.
Frogsicle
Teacher Name:
__________________________
Student Name:
_________________
CATEGORY
Experimental
Hypothesis
Conclusion
Scientific
Concepts
4
3
2
1
Hypothesized
relationship between
the variables and the
predicted results is
clear and reasonable
based on what has
been studied.
Hypothesized
relationship between the
variables and the
predicted results is
reasonable based on
general knowledge and
observations.
Hypothesized
relationship
between the
variables and the
predicted results
has been stated,
but appears to be
based on flawed
logic.
No hypothesis
has been
stated.
Conclusion includes
whether the findings
supported the
hypothesis, possible
sources of error, and
what was learned from
the experiment.
Conclusion includes
whether the findings
supported the
hypothesis and what
was learned from the
experiment.
Conclusion includes
what was learned
from the
experiment.
No conclusion
was included in
the report OR
shows little
effort and
reflection.
Answers illustrate an
accurate and thorough
understanding of
scientific concepts
underlying the lab.
Answers illustrate an
accurate understanding
of most scientific
concepts underlying the
lab.
Answers illustrate a
limited
understanding of
scientific concepts
underlying the lab.
Answers
illustrate
inaccurate
understanding
of scientific
concepts
underlying the
lab.
Author: Jack Lester, Yakima WATERS Project, CWU, 2009-2010