Homeostasis and Crypsis: An Inquiry into in Color Change in
Canyon Tree Frogs
Oliver Hyman and Jackie Christoffel
This lesson takes an inquiry based approach to increase student understanding of
physiological tradeoffs using Canyon tree frogs (Hyla arenicolor) as a model organism.
Using easy-to-assemble enclosures, students will be able to test the importance of cryptic
coloration and homeostasis in this intriguing species of color changing frog. By allowing
students to empirically test the validity of important scientific concepts, this lesson not
only helps to internalize their understanding of homeostasis and camouflage, but also
enhances their mastery of the scientific method.
Key words: Adaptation, Homeostasis, Crypsis, Thermoregulation, Endothermy,
Ectothermy, Amphibian, Frog, Experimentation, Manipulation, Independent and
Dependent Variables,
Grade level: 8-12 * this lesson was designed to meet 8th grade science standards.
Duration: 6–12 class periods (dependent on time available and student ability)
SCIENCE STANDARDS:
Strand I: Inquiry Process
Concept 1: Observations, Questions, and Hypotheses
PO 1&3: Students will formulate questions and hypotheses from
their observations
Concept 2: Scientific testing/Controlled Investigations
PO 1: Students will learn proper handling/safety with live organisms.
PO 2-5: Students will design and conduct controlled experiments to test their
hypotheses.
Concept 3: Analysis and Conclusions
PO 1-8: Students will assess the results of their experiment using basic graphs,
interpret their results in relation to their initial hypothesis/predictions, evaluate
their validity and suggest future studies
Concept 4: Communication/Assessment
PO 1-5: Group work will develop communication
Write up/ppt. presentation of experiment and results
Strand II: Nature of Scientific knowledge
Concept 2: Nature of scientific knowledge
PO 1: Students will apply the scientific method to test scientific concepts.
PO 4: Explain why claims may be questionable if based on small sample
sizes, biased studies, or no control.
Strand IV: Life Science
Concept IV: Diversity, adaptation, and behavior
PO 1: Demonstrates how an organism’s behavior allows it to survive
PO 2: Describes one specific mechanism for how an organism can maintain a
stable internal environment while living in a constantly changing external
environment.
PO 3: Determine characteristics of organisms that could change over several
generations. Can be tied into this through a simple “dot” exercise.
PO 6: Describe factors that allow for the survival of living organisms.
- protective coloration, thermoregulation
LESSON OVERVIEW:
This lesson is meant to enhance students’ understanding of homeostasis and
protective coloration through both formal lecture and scientific inquiry. Students will
be introduced to important concepts including Homeostasis, Ectothermy,
Endothermy, Poikilothermy, Homeothermy, and Crypsis. Following a brief
introduction, students will be asked to test the validity of these concepts by designing
experiments using Canyon tree frogs and easily manipulated microhabitats. Student
designed experiments will not only solidify their understanding of these concepts, but
also improve student ability to implement the scientific method. Throughout the
course of the lesson, student learning will be assessed through the use of informal
review, in class worksheets, quizzes, tests, and a final lab write up.
MAIN OBJECTIVES
Science Content:
1) An organism’s habitat is the supportive environment in which it lives.
2) Anthropomorphism is attributing human thoughts and feelings to nonhuman
organisms.
3) Frogs are amphibians and therefore ectotherms that have to behaviorally control
their body temperatures. Metachrosis (or color changing) is one way to do this.
4) Homeostasis (maintaining a stable internal environment) is important for an
organism to optimally perform basic functions such as digestion, running, hunting,
attracting mates, etc.
5) Ectothermy is getting heat from an outside source. Endothermy is generating heat
internally/metabolically.
6) Poikilothermy is having a variable body temperature. Homeothermy is having a
stable body temperature.
7) Ectothermy is advantageous because it requires less energy than Endothermy.
Endothermy is advantageous because it allows organisms to always perform
optimally.
Conducting Investigations:
1) Conduct structured investigations to determine the importance and validity of
metachrosis and behavior in maintaining a stable internal temperature.
a) making observations
b) forming questions and hypotheses
c) experimental design
constants, independent, and dependent variables
d) Recording, organizing, and interpreting data
2) Demonstrate respect for living organisms while conducting investigations
Building explanations:
1) Describe and quantify habitat color preferences at different temperatures.
2) Construct graphs/tables to show trends in the data and interpret the graphs.
3) Interpret results with respect to hypotheses regarding thermoregulation and
homeostasis.
4) Evaluate validity of results.
5) Communicate results using oral presentation and written lab report.
Materials:
~10 habitat boxes: Cardboard boxes constructed with velcro attachment sites for 8
ceramic tiles. (click here for instructions).
~160 ceramic tiles Standard ~4 in.X 4 in. tiles. 80 black and 80 white on the back.
You can buy these in bulk from Home Depot for $0.15/tile.
~160 velcro fasteners to stick to the back of the tiles
~10-20 Canyon tree frogs* (Hyla arenicolor) – click here for notes on husbandry.
~2 heat lamps.
~1 rubber snake
~Saran wrap
~Rubber bands
~1 aquarium with tight, metal lid (10-20 gallon)
~10-20 clear plastic cups (use these to house frogs individually during experiment)
~10 “colorimeters”
~10 rubbermaid shoe boxes or any clearish container of comparable size.
~Rocks
*if Canyon tree frogs are not available, other tree frogs (family Hylidae) or anoles purchased from
local pet stores will also work.
Worksheets:
Initial assessment worksheet
Observations worksheet
Notes for day 2 (Print the “student notes for powerpoint” in note taking format for students)
Project design worksheet
Analysis worksheet
Lab report grading rubric
Final Assessment Test
Powerpoint Lectures:
Introduction to Homeostasis, Camouflage, and Amphibians and Making Observations
Review questions:
For a list of important review questions click here
Procedures:
PREPARATION:
Previous Week
Construct habitat to hold frogs.
Collect frogs from field, or contact local expert to help (I recommend
getting in contact with local the local fish and game non-game division, or
email me: oliverhyman@hotmail.com)
Construct habitat boxes. Gather other materials including lamps, heat lamp
bulbs, observation containers, and colorimeters.
Review lecture material.
Reserve computers for “graphing day” – Day 5
Day 1
Print initial assessment worksheet and observation worksheet
Set up stations with frogs in observation containers
Day 2
Print notes for powerpoint
Day 3
Project design worksheet
Day 4
Print analysis worksheet
Day 5
Print lab report rubric
Day 6
Print final assessment test
EXECUTION:
This lesson builds upon itself, so it will be very important to remind students throughout
the week to keep all of the worksheets, quizzes, notes, etc. together and well organized in
an easily accessible notebook/folder/binder.
PART 1: MEET THE TREE FROG
Synopsis: students observe tree frogs to familiarize themselves with their external
structures and how they move and behave. They record what they know about frogs and
list what they would like to find out about them.
Objectives: Students should demonstrate respect for living organisms while learning how
to make and record basic observations.
Preparation:
1) Set out individual frogs in 6-12 separate observations chambers.
2) Print out assessment and observation sheets.
Step-by-Step:
Day 1:
1) Initial assessment quiz (15 min). Hand out the initial assessment sheet. This
will give you an idea of weaknesses and misconceptions in the students’ background
knowledge, and will help you to assess points that will need to be stressed and those that
can be glazed over in following lectures. Give them 20 minutes tops. If they don’t finish
no big deal. Once they are all handed in proceed to step 2.
2) Explain rules of handling frogs/respect for living organisms (5 mins):
a) Be extremely gentle. Do not squeeze or throw.
b) Do not rub eyes, nose, or mouth after handling
c) Must remain very quiet and avoid bumping tables and crowding over
enclosures during observation
d) DO NOT freak out if frog gets away. Just stay calm, recapture the frog
and continue with the experiment.
e) DO NOT tap on glass or try to rile the frogs up.
3) Observations (40 min): Set up a couple different “stations”. Warm room. Cold
room. Light colored room. Dark colored room. Rocky room. Feeding room. Dark room.
Predator room. Multiple frogs room. Hand out observation worksheets. Have students
rotate to each station for 5 minutes and record observations. Encourage students to write
down all their observations, no matter how trivial. Remind them to remain quiet and not
disturb the frogs’ natural behavior. During this time teachers should be working the
classroom, asking questions, encouraging ideas, etc. BE SURE STUDENTS KEEP
THEIR OBSERVATION SHEETS. This concludes the first day.
PART 2: FROG BIOLOGY, HOMEOSTASIS, AND ANTHROPOMORPHISM.
Synopsis: Class discusses observations from previous class period, and addresses the
issue of anthropomorphism. After discussion students are introduced to the concepts of
homeostasis and related terms.
Objectives: Frogs are amphibians and therefore ectotherms that have to behaviorally
control their body temperatures. Metachrosis (or color changing) is one way to do this.
Homeostasis (maintaining a stable internal environment) is important for an organism to
optimally perform basic functions such as digestion, running, hunting, attracting mates,
etc. Ectothermy is getting heat from an outside source. Endothermy is generating heat
internally/metabolically. Poikilothermy is having a variable body temperature.
Homeothermy is having a stable body temperature. Ectothermy is advantageous because
it requires less energy than Endothermy. Endothermy is advantageous because it allows
organisms to always perform optimally.
Preparation:
1) Review powerpoint presentation for Day 2.
2) Print powerpoint presentation in note taking format to give to students.
Step-by-Step
Day 2:
1) Discussion of observations (30 mins). First, pass out the note taking sheets for
your lecture. Next have students volunteer their observations and write them up on the
board. See if students have any biological explanations for their observations.
This is the opportunity to address the issue of anthropomorphic observations.
Invariably, students will come out with observations like, “the frog likes heat” or “the
frog hates the snake”. These statements are incorrect because they imply that the students
are able to observe a frog’s feelings. This is beyond the abilities of our senses. All we can
do is observe if the frog prefers one thing over another. The students are projecting their
own feelings upon the frogs, when there is no way for us to really know how a frog feels
or if it even has feelings. This is what is known as anthropomorphism, or giving human
emotions to things that we can only observe. We cannot know an animal’s feelings or
emotions. All we can know are their preferences. It is important to make these
distinctions because once we begin to project our own feelings on the animals we are
studying, we begin to introduce bias into our studies.
Write a few examples of these kind of statements and have students correct them.
Example: “the frog likes the dark”  “the frog moves less when it is dark”
We have no way to know if the frog likes or hates the dark, all we know is that it
moves around more in the light than in the dark.
So what is a preference? And how do we show whether an animal has preferences or
not?
A preference is shown when an animal is given two or more options (be they
different habitats, foods, mates, etc) and consistently chooses one over the others. For
example if you took everyone in the room and gave them the choice between dog food or
a piece of fruit, almost all would choose the fruit. That is a preference.
Next you introduce them to a fair test of preference. First, make this statement,
“For example, I could give _Student X_ a choice between coke and pepsi.” Then ask
student x which she prefers. Then you say, “therefore 8th grade students like coke more
than pepsi” Immediately students will begin to disagree that they like pepsi better. Ah ha!
So how do we make this a fair test? Now present them with a more rigorous example and
have them pick out the problems with it.
Ex. Ted’s Experiment:
Ted is examining frog habitat preferences. He puts a frog on top of a piece
of sand paper and the frog immediately jumps off. It then lands on a piece
of yellow tape. Ted writes, “Frogs like yellow tape the best.” Do you
agree with his conclusions? What is wrong with them?
2) What is a Frog? What is Homeostasis? Lecture (45 min) This should be a
brief review of the animal kingdom and the Class Amphibia. Show them the different
kinds of amphibians (Caecilians, Salamanders, and Frogs). Tell them what all amphibians
have in common: Ectothermic, Permeable skin, no shells on eggs, often associated with
aquatic breeding and terrestrial habitats.
Suggestions for directing class:
1) Open up with question: what is a frog? Is it an animal? Is it an
amphibian? What is an amphibian?
2) Allow students a few minutes to discuss what they think in
groups before going into lecture.
PART 3: EXPERIMENTAL DESIGN: WHY DO FROGS CHANGE COLOR?
CRYPSIS OR METACHROSIS?
Synopsis: Class develops different hypotheses for the questions “why do frogs change
color” Students then design and conduct an experiment to test the competing hypotheses
of crypsis and metachrosis.
Objectives: Frogs may change color for either crypsis (camouflage) or metachrosis (to
thermoregulate). Using habitat boxes students can make the background light/dark and
hot/cold to design a box and experiment that will determine which of these competing
hypotheses is correct. Students will learn to distinguish between hypotheses (crypsis and
metachrosis) and predictions (the frog will get lighter or darker). Students will learn to
identify independent/manipulated variables (tile color and temperature) and dependent
variables (frog color). Students will learn experimental design and the importance of
objective quantification (using colorimeters to measure color). Students will use graphs to
interpret their data and determine whether it supports or rejects their competing
hypotheses. Finally, they will learn to write a formal lab report of their experiment and
results.
Day 3: Experimental Design
Preparation:
Print copies of experimental design worksheet and colorimeters for each student. Also,
have boxes and tiles ready to be distributed to each student group. Be sure to review and
fully understand the experimental design worksheet.
Step-by-Step:
1) 15 minutes: begin with quiz/review game to review the concepts we learned
yesterday.
2) Remainder of class:
Experimental Design
The goal is to come up with one experimental design that the entire class can do as a
group and combine all their data at the end. Hand out experimental design worksheet,
habitat boxes with tiles, and colorimeters for students to mess with. Tell students they
will be able to chose black or white tiles and make them hot or cold as they see fit. Each
group will work individually to develop an experiment to test the question: “Why do
frogs change color?”
First make sure each student is able to come up with the following hypotheses for
why frogs change color: Crypsis and Metachrosis (see worksheet for details). Once
students understand these two hypotheses, allow them time to come up with their own
experimental designs to test these hypotheses. The worksheet will lead them step-by-step
through this thought process.
Once the each group has completed the worksheet, have groups trade worksheets
and evaluate each other’s experiments. After students have had time to look at someone
else’s experiments then have them volunteer an experimental design that they like best.
Discussion:
Now it is your job to direct a group discussion of this experimental design. Using the
Chalk board, have a student draw how the tiles will be set up and what their steps will be.
Your job is to criticize different aspects of the design that you feel are weak. The first
part is coming up with a design that has clear predictions. This will be the hardest part for
the students.
They need to design experiments that have clear predictions for one hypothesis
and not another. For example, a student comes up with the following design: You have a
half black and half white box, you put a frog in for 10 minutes and observe which color it
picks. So now you must ask students the following question: “What does our hypothesis
predict will happen?”
Frogs could pick the black tiles to blend in or to heat up, or maybe they’ll pick the
white tiles to cool off and blend in we can’t say for sure. This experiment is bad for two
reasons. 1) it doesn’t have a clear prediction that supports one hypothesis and not another
2) it doesn’t really address the initial question of why do frogs change color? This
experiment actually address the question, Which color of tile do frogs prefer? Which is
fine, but is not our initial question.
The best design is as follows: Have a box with all white all cold tiles. (or an all
black all hot box). Then measure the frog color before and after you put it in this box for
about 10 mins. Now we have clear and opposing predictions for each hypothesis: Crypsis
predicts the frog will turn lighter to blend in with the white tiles while Metachrosis
predicts the frogs will turn darker to absorb more heat while on the cold tiles.
Allow students to figure this out on their own. They can do it. I’ve seen it done.
Once they come up with the right box design then you need to really nail down the
procedure: What parts of the frog are they going to measure. How do we ensure that
everyone measures the same way? When do you want to measure the frog? How long
does the frog need to be in the box? How many frogs should we use? How many trials
should each group do? Where do we keep the frog when it’s not in the box? How long
should we keep it out of the box? How are we going to record the data? What should our
data table look like? Once they’ve got all this stuff figured out then you can do the
experiment.
Day 4: Conducting the Experiment
Preparation: Print experimental analysis worksheet. Have frogs in individual containers
with some water to ease distribution to groups. Have tiles prepared (heated or chilled
accordingly).
Daily Plan:
1) 15 minutes: Review of concepts from Day 2.
2) Remainder of class: Conduct experiment and begin Analysis worksheet
Review the experimental procedures that were decided upon during last class and
write them on the board/ppt, so all can see the step-by-step process. Also, review rules for
handling animals carefully and respectfully. Have the boxes on the desks and have tiles
(cold/hot) ready to go at the start of class. Also, I recommend putting frogs into
individual plastic cups with a bit of water in the bottom. You can cover these cups using
Saran wrap and rubberbands. Then you can use these cups to hold frogs in-between trials.
Have students work in original groups, and delegate responsibilities so that everyone has
a job. Have students develop table to record data and be sure that each group holds onto
their data until next class.
During down time students should be working on the analysis worksheet. They
will only be able to answer up to question 5.
Day 5: Data Analysis
Preparation: review experimental analysis worksheet and print lab report rubric be sure
you understand the answers. Obviously, these answers will change according to the
results and experimental design your class came up with. The answers on this sheet are
just an example of what could happen.
Daily Plan:
1) First 15 minutes: Review of concepts.
2) 30 minutes: Combine data, analyze, and finish analysis worksheet
The goal for today is to combine results from the entire class, construct a bar graph to
help interpret these results, and finally to use these results to complete the question on the
experimental analysis worksheet.
Have students get out their data tables from last class. Then draw the following table up
on the board (but obviously it should be blank and big enough for each group to fill in the
data for all of their trials:
Trial
Leg
Spots
Back
Total
Lighter?
Darker?
1
2
3
5
10
1
3
4
6
13
X
2
3
3
4
10
2
3
4
4
11
X
3
Etc.
Then have one member or each group come up to the board and fill in all the data
from all their trials. The idea here is to combine data from all the experiments and see
how many total times the frog got lighter or darker or stayed the same.
Once all the data is up your job is to show students what is going on by explaining
what all these numbers mean.
a) Count the total number of trials conducted (this will probably be like 30 or so)
b) Count the number of trials in which the frog got light/darker/stayed the same
and white these total on the white board.
These totals may look something like this:
Same = 4
Darker = 24
Ligher =2
Once students understand what these numbers mean you should have them individually
design bar graphs to represent the data. Be sure that they :
a) label axes
b) give an informative title
c) allow you to determine the meaning of each bar
Below is an Example of what their graphs should look like:
Color change in Canyon Treefrogs:
Crypsis vs. Metachrosis
number of trails
30
25
20
15
10
5
0
Darker
Lighter
Same
color change
Students should individually complete this graph and the experimental analysis
worksheet. You can choose to collect the worksheet or go over it as a group. However,
you like, but is important that they understand their results and which hypotheses they
support or reject.
4) Once this sheet has been completed to you satisfaction, students should begin writing
their lab reports following the guidelines of the lab rubric.
5) Remind students about closed note quiz on Monday.
Day 6: Final Test
Preparation: Print final assessment worksheet
Daily Plan:
1) 45 minutes – 1 hour: Test: Administer final assessment worksheet. This will
cover all major concepts from last week as well as assess whether students have met the
objectives of this lesson.
2) Remainder of class: allow students to work on lab report.
*Note to teachers: Because this lab introduces students to the idea of cryptic coloration and
predator avoidance, it sets the stage for a perfect transition into the jellybean lab or dot lab. This lab helps
to demonstrate the process of natural selection and meets a number of state standards. I highly recommend
using the jellybean experiment as a follow up lesson to this one.
Canyon Tree Frog Lesson
Initial Assessment Questions:
Please answer the following questions to the best of you ability.
1) Why do all humans have a body temperature of 98.6 degrees?
2) Why do chameleons change color?
3) Why are warm blooded animals called warm blooded and why are cold blooded
animals called cold blooded?
4) Can you name a warm blooded animal? How about cold blooded?
5) Which is better in terms of survival, being warm blooded or cold blooded? Why?
6)What is homeostasis?
7) What is an amphibian? What makes an animal an amphibian?
8) How would you define what a frog is? What would you like to know about frogs?
Frog Observation Sheet
Name___________________
YOUR JOB IS TO WRITE DOWN ANYTHING THAT YOU THINK IS
INTERESTING ABOUT THE FROGS YOU OBSERVE.
Station:
Observations:
What color is the frog? Does it blend in well with its background?
Does it change color?
Station:
Observations:
What color is the frog? Does it blend in well with its background?
Does it change color?
Other observations?
Station:
Observations:
What color is the frog? Does it blend in well with its background?
Does it change color?
Other observations?
Table Game Review Questions
1) Name one attribute that makes an animal an amphibian
2) Give me an example of an amphibian.
3) What do you call an animal that get its heat from an outside source?
4) Having variable body temperature.
5) Having a constant body temperature.
6) Producing your own body heat internally.
7) Maintaining a constant body temperature.
8) Maintaining a constant internal environment
9) Give me one reason homeostasis is important.
10) Changing colors to aid in thermoregulation
11) Example of an endothermic animal
12) Example of an ectothermic animal
13) Example of a cold blooded animal
14) Example of a warm blooded animal
15) Name one advantage of being endothermic
16) Name one advantage of being ectothermic
17) Giving human traits and emotions to animals
18) Why is anthropomophisizing bad?
19) Having camouflage to avoid predators.
20) What does permeable mean?
21) Name one method ectotherms use to thermoregulate.
22) Errors in an experiment due to beliefs of the experimenter.
23) What’s wrong with this statement, “Bird love pine trees”
24) When an animal consistently chooses one thing over another.
Frog Lesson Experimental Worksheet:
Names of Group Members: __________________ ___________________ __________________
Answer the following questions completely:
1) Come up with 3 hypotheses that may be answers to the following research question:
Why did the frogs change color?
(Example: The frogs change color to communicate with each other.)
The answers we’re looking for are:
1)Crypsis: changing color to hide from predators/camo
2)Metachrosis: changing color to thermoregulate (they get dark to heat up and light to cool off)
2) Do any of these hypotheses relate to any of the concepts we learned in class (such as homeostatis or
crypsis)? Please explain how it relates to these ideas.
Yes, metachrosis relates to thermoregulation and homeostasis. Since the frog is an ectotherm it gets its body
heat from the sun. Therefore, changing color from light to dark makes a difference in how quickly it heats
up. This is an exmple of thermoregulation and thermoregulation is a type of homeostasis.
3)Design an experiment using the materials we have in class to see if frogs change color for the purpose of
crypsis or metachrosis (or both/neither).
a) What is the question you want to answer?
Why does the frog change color?
b) What is your hypothesis? (ie your answer to this question)
To blend in (crypsis) or to heat up (metachrosis) or both
c) Draw how your frog habitat will be set up.
Basically students decide whether they want these blocks to be black/white and hot/cold.
d) Give step by step instructions for how your experiment will be conducted. Be sure to include the number
of times the experiment must be repeated.
This should be something like: 1)measure frog color, 2) put frog in box, 3) give 10 minutes for frog to adjust
4) Measure frog color again 5) take frog out for 10 mins. 6) Repeat.
It is important that students remember1) to measure the frog color before and after. 2) to come up with a
standardized way to measure frog color (ie what parts (back?belly?legs?spots?) do you measure, how do
you measure them?(just eye it or use colorimeter?), when do you measure them (before and after,etc).
c) What variables will you be measuring, and how will you record them?
We will record the color of the frog’s back, legs, and spots before and after being in the box using a
colorimeter
d) Draw a table for recording your data.
Trial
1
1
2
Time
10:00
10:10
10:20
Leg
3
4
Back
4
5
Spots
6
6
Total
13
15
d) Tell me what your independent, dependent, and constant variables are.
Independent – Tile temperature and color
Dependent – Frog color
Constants –Time in container, type of tiles, size of box, colorimeter, species of frog, etc.
e) If your hypothesis from 3b is correct, what do you predict will happen in your experiment? This should
be an “if…then” statement. Ex. If frogs change color for crypsis, then they should turn black in an all black
container.
Canyon Treefrog Final Assessment Test: Homeostasis
Match each of the following terms to its definition. Some letters may be used more
than once ( X points each):
1) Homeostasis__e___
2) Endotherm__f___
3) Ectotherm__j___
4) Poikilotherm___c__
5) Homeotherm__g___
6) Thermoregulation__h___
7) Metachrosis___i__
8) Crypsis __b___
9) Anthropomorphism_a____
10) Cold-blooded___j___
11) Bias___d__
a. Giving human traits and emotions to
nonhuman organisms
b. Changing color to blend in with your
environment, like camouflage.
c. An animal that has a variable body
temperature
d. Errors in an experiment due to the notions
or beliefs of an experimenter
e. Maintaining a stable internal environment
through physiological or behavioral
responses
f. An animal that produces its own heat
internally
g. An animal that maintains a constant body
temperature
h. maintaining a stable body temperature
through behavioral or physiological
responses
i. Changing colors to aid in absorption of
heat/thermoregulation
j. An animal that receives its heat from
external sources
12) Circle which animal(s) is/are Endothermic
a) Mouse
b) Lizard
c) Lion
d) Fish
e) Eagle
13) Circle which animal(s) is/are Ectothermic
a) Cat
b) Human
c) Penguin
d) Crocodile
e) Caecilian
14) Circle the animal(s) that is/are Poikilothermic
a) Bear
b) Beetle
c) Fish
d) Squirrel
e) Whale
15) Circle the animal(s) that is/are Homeothermic
a) Horse
b) Gila Monster
c) Fly
e) Rat
f) Rabbit
16) Why is Homeostasis important for an animal to survive. Give two good reasons?
Animals must maintain a stable internal environment in order to conduct
basic physiological/chemical processes such as running, digesting, hunting,
reproducing, etc.
17) Is it possible for an animal to be Ectothermic and Homeothermic? Be sure to
explain your answer.
Yes! If are in a place, say the tropics, where it stays warm all the time you
can be and ectotherm and still keep your body at the same temperature.
18) Name one advantage and one disadvantage of being Ectothermic:
Advantage: Consume less energy, need less food, bring more biomass into the
system
Disadvantage: Not always at optimal temp, limits habitats, less predictable,
limits activity
19) Which do you think is better, being endothermic or ectothermic? Defend your
answer using two specific examples of why one is better/worse/just as good as the
other.
Students can answer this either way as long as they defend their arguments.
Example of full credit answer: Endothermy is better than Ectothermy. Although
endotherms use a lot more energy to maintain a constant body temperature, they
still have the huge advantage of always being at an optimal temperature to mate or
evade predators, or digest food.
20) Which graph represents a poikilotherm, A or B? Explain your answer?
Chart B
30
25
20
15
10
A
7: M
00
A
9: M
00
AM
11
:0
0
AM
1:
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Chart A
21) Name 3 attributes that make an animal an amphibian?
1)Permeable Skin
2)Two life Stages (aquatic and terrestrial)
3)No shell on eggs
4)Backbone
22) Circle the animals below that are amphibians. Tell me why the ones that you did
not circle are not amphibians.
Penguin, Alligator, Salamander, Earthworm, Tadpole, Snake
Penguins Alligator and Snakes do not have 2 life stages, they do not have permeable skin,
and they do not lay eggs with no shells.
23) What is Anthropomorphism? Give one example.
Giving human traits or emotions to nonhuman organisms. For example, saying, “Cats
hate lettuce.” would be anthropomorphizing.
24) Why is it bad to anthropomorphize?
Because it introduces subjectivity, bias, and opinions of the experimenter, and
science/experiments should be unbiased.
25) What is a preference?
This is when given a choice between two or more things an animal consistently chooses
one option over the others.
26) Bill is examining Dog food preferences. He puts a dog on in a room with wet
food in one corner and dry food in the other. The dog immediately goes for the wet
food. Ted writes, “Dogs love wet food the best.” Do you agree with his conclusions?
Explain your answer thoroughly. Do a good job, because it’s worth a lot of points.
I disagree for a few reasons. 1) He is anthropomorphizing. He should say dogs like or
prefer wet food, not love. 2) He is overstating his case. He has only done one trial with
one dog and one set of options. It could be a weird dog that isn’t representative of most
dogs, It could be a bad brand of dry food. The dog may choose differently on a different
day, so to say categorically that dogs prefer wet food the BEST is wrong. We need more
rigorous experiments to be sure.
Experimental Analysis Worksheet:
1) What was the initial question our experiment set out to answer?
Why do frogs change color?
2) What were our hypotheses?
Crypsis and Metachrosis
3) What are the scientific concept(s) that our experiment tested?
Homeostasis, thermoregulation, ectothermy, crypsis. Etc.
4) What were the independent and dependent variables in our experiment?
Independent – tile color and temperature; Dependent – frog color
5) How did we predict our dependent variable would change in response to our
independent variable if each of our hypotheses were correct?
If crypsis is correct then frogs in a cold white box should turn white to blend in.
If metachrosis is correct then frogs in a cold white box should turn dark to heat up.
6) What were the results of our experiment? ie how many frogs did we test in total?
How many trials did we do for each frog? In total how many times did a frog
change color as we predicted it would? Use tables or graphs in your answers.
We sampled 10 frogs ten times each for a total of 100 trials. In 90 out of
100 trials the frogs turned lighter.
7) What was the major outcome of our experiment?
Canyon tree frogs change color for crypsis.
8) Did this outcome support or reject each of our hypotheses? Explain.
It supported crypsis and rejected metachrosis. 90 out of 100 times the
frogs turned lighter as crypsis predicted they should. Only 10 out of 100 times did
they turn darker as metachrosis would predict. Therefore our results support crypsis
as the reason frogs change color
Habitat Boxes
Velcro Attachment
4.75”
4.75”
9”
Cut box from cardboard, fold up side walls and secure with duct tape. Once box is
Constructed you can cover with saran wrap secured by a strong rubber band.
Basic Amphibian Care:
You should keep the frogs in an aquarium as described below. Once you have this
aquarium set up all you need to do is feed each frog about two crickets per a week
and change the water once a week. Very easy.
Treefrog Aquarium
timer
timer
Regular lamp
Heat lamp
Rocks
Rocks
Canyon tree frogs are a basking species of frog. They normally like to take a dip in the
water early in the morning then heat up throughout the day. To create the ideal habitat
For this you tilt the aquarium so there is a deep pool of water on one side and not the
other. Then stack up rocks as shown to provide basking sights and shelter. Put a metal
Mesh lid on the top that is tight, otherwise they will crawl out. On top of the lid you put two
Lamps, each of which should be connected to a timer. The regular lamp should turn on in
The morning (7am) and off at night (7pm). The heat lamp should be set to turn on for about
One hour four different times throughout the day (say 8am, 11am, 2pm, and 5pm). Water
Should be changed weekly and it is recommended to use aged tap water as opposed to
Water straight from the tap that still has a lot of chemicals in it.
Laboratory Report: Canyon Treefrogs and Color Change
Below is a list of the sections and requirements for your lab reports. These will be done
individually. Please fill in each section and be sure to follow the directions carefully. This
assignment is worth 40 points. Six of the 40 points will come from formatting, so please
follow the formatting directions below:
Format (6 points)
- Methods and Results written in past tense and paragraph form (2)
- Standard formatting: double-spaced, 12 point font, 1” margin (1)
- Spelling and grammatical errors minimal (2)
- Information is presented in appropriate sections (i.e. no results in introduction,
no interpretation in results) (1)
Title (2 points)
The title should be a short description of your main question or findings. It should
not be uninformative, (for example, “Frogs are cool” or “Homeostasis” are not a
good titles) (2)
Abstract (4 points)
This is a very short summary of your entire experiment: This sections should
introduce the behavior of interest, present our question and hypotheses, briefly
describe methods, state the main result, indicate your conclusion, and relate
conclusion to other studies and/or broader ideas (3)
- short (<300 words) (1)
Introduction (6 points)
This is your chance to give your reader some background information, so that
they know what your study was about and why it might be important. For full
credit, you should make sure that your introduction:
- Introduces background about the animal behavior we studied(for example:
metachrosis, crypsis, thermoregulation, homeostasis, etc.) (1)
- Provides relevant background information about the study organism (1).
- Describes the importance of the behavior of interest, including its role in the
survival and/or reproduction of the organism and other relevant information
(1)
- Research Question clearly stated (1)
- Hypothesis(es) are clearly stated (1)
- Predictions (if….then statements) are clearly stated for each hypothesis. (1)
Methods (6 points)
This section should explain how the experiment was run. It should not be a list.
You should clearly describe how the experiment was conducted, how you set up
your box, and how you recorded the data. Feel free to include figures or diagrams
to aid in your explanations (for example, a drawing of the boxes would be
helpful). Along with explaining how the experiment was done, be sure that your
methods section:
-
-
Clearly identifies independent variables and dependent variables, including
units. (2)
Clearly describes experimental design, including how independent variables
were manipulated and other variables controlled, and the number of frogs
tested and how many times each frog was tested (2)
Clearly describes method of measurement/observation/quantification of
dependent variable(s) (2)
Results (6 points)
This section should explain your results, but it should not go into to detail about
why you got these results. Save this for the Discussion. Your results section must
have at least one table or figure. More than one table or figure is welcome. Be
sure that your results section:
- Includes total sample sizes. (Example: “Twenty frogs were tested 4 times each
for a total of 80 trials”)
- Describes relationship between independent and dependent variable (2)
- Numerical results reported (example: Seventy five times out of a 80 trials, the
frog got darker).(1)
- Figure(s) and/or table(s) clearly show the main result(s); Does not include
table of all the raw data (2)
- Figures and tables include units and captions that describe information
presented, and are referred to in the text (each student must generate their own
graphs)(1).
Discussion (8 points)
This is your chance to explain why you got the results you got and tie these results
into your initial hypotheses and predictions. You should also mention potential
sources of error, but error analysis should not be the bulk of your discussion. Be
sure that your discussion:
- Explicitly compares results to predicted results of each hypothesis (1)
- States conclusion in context of original question and hypotheses (1)
- Conclusion is a logical and correct interpretation of results (2)
- Discussion of error is specific and describes potential effects on results. error
analysis should not be the bulk of the discussion(0.5)
- Relates findings to other studies of behavior of interest (1.5)
- Identifies future directions for research prompted by results of this study
including clearly stated new research questions and hypotheses (2)
Literature Cited (2 points)
- At least one book/paper/website is properly cited in text: (Author, year) (1).
- All citations in text are found in literature cited section and vice versa (0.5)
- Citations are complete: Author(s), Year. Title, Journal(Volume):Pages (0.5)
Total 40 points
Colorimeters: Print in black and white and cutout
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