FNR-430-W UNIT 3 Reptiles, Amphibians, and the Scientific Method

Purdue extension

FNR-430-W

Lucas Woody, Heather Powell, Estelle Coffin, and Rod N. Williams

Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907

Overview ............................... 2

Teacher Information Packet ................3

Lesson 1: Habitat Selection ................ 5

Reptiles and Amphibians Worksheet .........7

Life Cycle Worksheet ......................9

Habitat Poster ..........................11

Reptile and Amphibian Images .............12

Habitat Selection Worksheet ..............13

Herpetologist Badges .....................15

Lesson 2: Icy ’N Hot Crickets ............... 17

Ectotherm Experiment Worksheet ..........19

Lesson 3: Hot Rock ......................21

Hot Rock Experiment Worksheet ...........22

www.purdue.edu/nature

• UNIT 3 •

Reptiles, Amphibians,

and the Scientific Method

Reptiles and amphibians can be used to describe many scientific concepts,

including life cycles, thermoregulation, and the scientific method.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Estimated Time

Three 45–60 minute Lessons

Vocabulary

• Amphibians

• Basking spots

• Cold-blooded

• Ectotherms

• Herpetologist

• Metamorphosis

• Reptiles

• Thermoregulation

Unit Objectives

Students will be able to:

• Identify the differences and similarities

between reptiles and amphibians.

• Predict how temperatures affect

cold-blooded animals.

• Understand the importance of thermoregulation.

• Understand how reptiles and amphibians utilize

objects in their environment to thermoregulate.

Targeted Grade-Level Indiana Standards

K–5 Math Standards

1.5.5

2.1.12, 2.5.8

3.5.8

5.5.6

K–5 Science Standards

1.1.2, 1.1.3, 1.1.4, 1.2.7, 1.3.3

2.1.2, 2.1.3, 2.1.4, 2.4.1

3.1.2, 3.1.3, 3.1.4, 3.1.5, 3.4.1, 3.5.1

4.1.2, 4.1.4, 4.1.6, 4.2.5, 4.3.11, 4.3.13

5.1.1, 5.3.10, 5.4.7

K–5 English Standards

1.1.1, 1.6.1

2.6.1

Required Materials

• Teacher Information Packet

• Reptiles and Amphibians Worksheet

• Life Cycle Worksheet

• Habitat Poster

• Reptile and Amphibian Images

• Habitat Selection Worksheet

• Herpetologist Badges

• Ecotherm Experiment Worksheet

• Hot Rock Experiment Worksheet

• Desk clamp lamp with 60-watt bulb

• 20 crickets

• Rock (flat, slate, approximately 6–8 inches

wide)

• Thermometer

• Ice packs

• 3 Tupperware containers (clear)

• Reptile and Amphibian Worksheet

transparency

Unit 3 • Overview

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Acknowledgments

The authors would like to thank the Indiana licensed teachers Allison Marquis and Lee Sweet for allowing this plan to be presented in their classroom as well as reviewing the plan. The authors would like to give a

special thanks to the fellow students of the Nature of Service Learning class, who provided ideas and helpful comments on previous versions of this unit. Photos by Rod Williams, Brian MacGowan, and Dan Annarino.

Purdue University Agricultural Communication Service • Purdue University Cooperative Extension Service • Editor: Becky Goetz • Designer: Dan Annarino

03/11

UNIT 3 • Reptiles, Amphibians the Scientific Method

Reptile and Amphibian General Overview

Reptiles and amphibians represent a diverse collec-

tion of animals. In general, there are six major

taxonomic groups (three are reptile, and three are

amphibian). The groups and their general charac-

teristics are given below.

Reptiles:

• Snakes—long, tubular bodies covered in

scales; forked tongue; no legs

• Lizards—tubular body covered in scales,

generally long tail, four legs with claws

• Turtles—body covered in hard shell above and

below, four legs

Amphibians:

• Salamanders—generally very small, moist

skin, usually four legs, no claws

• Frogs—long back legs, very agile jumpers,

short front legs, moist and smooth skin

• Toads—long and strong back legs, great at

hopping, skin somewhat drier and warty

Amphibians are a group of animals that are very

well known for their moist skin. This moist skin can

dry out very quickly, thus amphibians need to live

in moist environments or near water. Amphibians

are so tied to the water that many spend a major

part of their life in the water (more on this in the

Life Cycle section). Many amphibians can be seen

around the edges of wetlands, lakes, streams,

ponds, etc.

Reptiles, unlike amphibians, are not as dependent

on water. Their bodies are covered in scales that

allow them to keep the water inside their bodies

and not dry out. Depending on the time of day,

most reptiles can be seen on rocks, logs, or on the

forest floor. During the hottest times of the day,

they will most likely be hiding (more on this in the

Thermoregulation section).

Although they are different, reptiles and amphibians

are generally studied as a group. A person who

studies reptiles and amphibians is known as a

herpetologist. (The field of biology focused on

the study of reptiles and amphibians is known as

herpetology.) However, there is a very key differ-

ence between the two groups: their life cycles.

Life Cycle

The life cycles of reptiles and amphibians are

remarkably different. Reptiles have three major steps

in their life cycle, whereas amphibians have four.

A brief description of each cycle can be seen below.

Reptile:

Egg [ Sub-adult [ Adult

Amphibian:

Egg [ Aquatic Larva [ Sub-adult [ Adult

Amphibians have an extra step within the life cycle:

the aquatic larva. These larvae hatch from eggs laid

in water (a pond, wetland, etc.). Larvae are adapted

to live in the water. Young larvae have gills for

breathing in water and a flat tail for swimming, and

they lack legs. After a period of time (a few days to

a few years), these larvae begin to metamorphose.

They lose their gills and develop lungs, begin to

grow legs, and absorb their tails (if they are frog or

toad larvae). They are then ready to live on land as

sub-adults. The name amphibian literally means

“two lives,” and it is important that they can live in

these two completely different environments.

Living both in water and on land allows them to use

a vast array of resources that many other species

cannot use.

Reptiles differ from amphibians in that they hatch

from eggs directly into sub-adults (or miniature

versions of an adult). Reptile eggs differ from

amphibian eggs in that they have leathery shells that

resist drying out (unlike amphibian eggs, which must

be in water). These eggs are usually laid in nests of

soil or leaves, covered to hide them from predators.

Teacher Information Packet

UNIT 3 • Reptiles, Amphibians the Scientific Method

Note: We are describing the general life cycles for

amphibians and reptiles. Some species within these

groups deviate from the general patterns. For more

details on unique life cycles, see the following

references: Salamanders of Indiana, Frogs and

Toads of Indiana, Turtles of Indiana, and Snakes and

Lizards of Indiana.

Thermoregulation

While the life cycles of reptiles and amphibians

differ greatly, both groups of animals are similar in

that they are cold-blooded. Cold-blooded animals

cannot generate heat in their bodies. Birds and

mammals (like ourselves) are warm-blooded and

use a process in our body (i.e., metabolism) that

creates heat from the food that we eat. However,

reptiles and amphibians generate very little heat

from food, and must obtain heat using another

method, thermoregulation.

(Note: The term cold-blooded is misleading in

that reptiles and amphibians have blood that can

be warm at times using the process described in the

following paragraph. A more accurate term for the

inability of an animal to generate its own body heat

is ectothermic. However, for simplicity, teachers with

younger students can use the term cold-blooded.)

The process of thermoregulation is simply when an

animal uses the environment around it to heat and

cool itself to a desired temperature. For instance, if

a lizard is too cold in the morning, it will lay out in

the sun until it becomes warm. On the other hand,

if the lizard becomes too warm, it may hide in the

shade under a rock or another object to cool down.

Animals have even discovered that some objects

(such as logs and rocks) become warmer than the

surrounding ground, and they use these areas as

“basking” spots to warm up more rapidly. If a cold

reptile or amphibian cannot bring its body to a

desired temperature, its body may not function

correctly. It may become slow, or may not be able

to digest food properly. Alternatively, when tem-

peratures skyrocket, many species use objects in

their environment to hide from the sun. By hiding

under moist logs or leaves on the forest floor, many

amphibians avoid drying out on hot days. Salaman-

ders are well known for hiding under the layers of

leaves on the ground, or under rotting logs that

hold moisture.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Estimated Time



50-60 minutes

Required Materials

• Teacher Information Packet

• Reptiles and Amphibians Worksheet

• Life Cycle Worksheet

• Habitat Poster

• Reptile and Amphibian Images

• Habitat Selection Worksheet

• Herpetologist Badges

• Reptile and Amphibian Worksheet transparency

Lesson 1:

Habitat Selection

This lesson helps students understand

the differences and similarities between

amphibians and reptiles, including

how they may select habitat.

Procedure

1. Pass out the Reptiles and Amphibians

Worksheets, Reptile and Amphibian Images

(one from each of the six taxonomic groups),

and the Life Cycle Worksheet.

2. Introduce the six different taxonomic

groups (turtles, lizards, snakes, frogs, toads,

salamanders). Help students fill in the blanks

for group characteristics on the Reptiles and

Amphibians Worksheets using the transparency.

3. Introduce the term herpetologist and explain

that the students are going to be herpetologists

today. Discuss how reptiles and amphibians

are similar and different. Explain that different

groups may select different habitat types

within an area.

4. Pass out the Herpetologist Badges.

5. Explain the difference between reptiles and

amphibians with respect to their life cycles.

Here, introduce the life cycle information

found in the Teacher Information Packet.

Help the students complete their Life Cycle

Worksheets.

6. Explain how reptiles and amphibians are

similar by using thermoregulation. Here,

introduce the information given in the

thermoregulation section of the Teacher

Information Packet. Have each student write

the definition of thermoregulation in a

complete sentence on his or her worksheet.

7. Pass out the Habitat Selection Worksheet.

8. Place a picture from each taxonomic group on

the Habitat Poster using information given in

the introduction to determine the most

suitable placement for each animal. Reasoning

for each placement is as follows:

• Snake/Lizard: as reptiles, snakes and

lizards do not need to live close to

water. Thick scales protect reptiles from

drying out. They do, however, need sun

and shade to help them thermoregulate.

• Frog/Toad: Because they are amphibians,

frogs and toads are in danger of drying

out and need to be close to water.

However, they also go through changes

UNIT 3 • Reptiles, Amphibians the Scientific Method

that allow them to live on land (i.e., they

develop legs and lungs).

• Salamander: Because it is an amphibian,

a salamander needs to live close to

water to prevent itself from drying out.

However, since it has very thin skin, it

also needs to stay in the shade, if it does

leave the water. (Note: all amphibians

live near water, since they lay eggs in

wet areas, as well).

• Turtle: Although turtles are reptiles and

have scales to help keep them dry, they

are actually very well adapted to live in

the water (with webbed feet and flat

shells for swimming) and spend almost

all of their time there. This is beneficial

for them, since it makes it harder for

predators to capture them, and because

there is plenty of food in the water.

(Note: turtles do lay eggs on land like

other reptiles).

9. During the activity, students will write the

appropriate taxonomic group name (i.e., turtle,

salamander) in each blank that correlates

with the Habitat Selection Worksheet.

10. After completing the activity, briefly review

the major difference (life cycle) and similarity

(thermoregulation) between reptiles and

amphibians. Inform the students that by

knowing these important attributes, they can

better understand how reptiles and amphibians

live in and use their environments.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Reptiles and Amphibians Worksheet • KEY

Turtles:

Dry body protected by hard _______________________

_______________________ legs, body covered in scales

Snakes:

Long, dry, tube-like body covered in scales

Forked _______________________

_______________________ legs

Lizards:

Dry body covered in scales

_______________________ legs, each toe has a claw

Frogs:

Long, powerful back legs, good for _______________________

Very moist, _______________________ skin

Toads:

Powerful back legs, good for _______________________

Skin drier than frog’s, covered in _______________________

Salamanders:

Small animal with moist skin

_______________________ legs, toes with no claws

REPTILES

AMPHIBIANS

* FOUR

* HOPPING

* JUMPING

* SHELL

* SMOOTH

* TONGUE

* WARTS

* ZERO

WORD

BANK

Shell

Four

Tongue

Zero

Four

Jumping

Smooth

Hopping

Warts

UNIT 3 • Reptiles, Amphibians the Scientific Method

Reptiles and Amphibians Worksheet

Turtles:

Dry body protected by hard _______________________

_______________________ legs, body covered in scales

Snakes:

Long, dry, tube-like body covered in scales

Forked _______________________

_______________________ legs

Lizards:

Dry body covered in scales

_______________________ legs, each toe has a claw

Frogs:

Long, powerful back legs, good for _______________________

Very moist, _______________________ skin

Toads:

Powerful back legs, good for _______________________

Skin drier than frog’s, covered in _______________________

Salamanders:

Small animal with moist skin

_______________________ legs, toes with no claws

REPTILES

AMPHIBIANS

* FOUR

* HOPPING

* JUMPING

* SHELL

* SMOOTH

* TONGUE

* WARTS

* ZERO

WORD

BANK

UNIT 3 • Reptiles, Amphibians the Scientific Method

Life Cycle Worksheet • KEY

Reptile Life Cycle (Lizard)

Eggs are laid in _______________________

Amphibian Life Cycle (Frog)

Eggs are laid in _______________________

Thermoregulation: _________________________

_________________________________________

2.4.

Eggs

Land

Water

The process by which

animals use heat from the environment as well

as objects in the environment to control their

body temperatures.

Eggs

Larvae

Subadult

Adult

UNIT 3 • Reptiles, Amphibians the Scientific Method

Life Cycle Worksheet

Reptile Life Cycle (Lizard)

Eggs are laid in _______________________

Amphibian Life Cycle (Frog)

Eggs are laid in _______________________

Thermoregulation: _________________________

_________________________________________

2.4.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Habitat Poster

UNIT 3 • Reptiles, Amphibians the Scientific Method

Reptile and Amphibian Images

Frog toad

turtle

lizard

Snake

SalaMander

UNIT 3 • Reptiles, Amphibians the Scientific Method

Habitat Selection Worksheet • KEY

Water/Dry Land

Water

Water/Shade

Dry Land/Sun & Shade

Frog/Toad

Snake/Lizard

Turtle

Salamander

UNIT 3 • Reptiles, Amphibians the Scientific Method

Habitat Selection Worksheet

Water/Dry Land

Water

Water/Shade

Dry Land/Sun & Shade

UNIT 3 • Reptiles, Amphibians the Scientific Method

Herpetologist Badges

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

Herpetologist

I am a Reptile and Amphibian Scientist.

Name: _________________________________

UNIT 3 • Reptiles, Amphibians the Scientific Method

Estimated Time



45 minutes

Required Materials

• Teacher Information Packet

• Habitat Poster

• Ectotherm Experiment Worksheet

• Heat lamp with 60-watt light bulb

• 30 crickets

• Ice packs

• 3 Tupperware containers (clear)

Lesson 2:

Icy ’N Hot Crickets

This lesson helps students understand

how temperature affects ectothermic

(cold-blooded) animals.

Procedure

1. Place ten crickets in each of the three Tupper-

ware containers before conducting the lesson

plan. One container will contain the ice packs,

one will have the heat lamp shining on it, and

the remaining container will have nothing

affecting the temperature. Label the crickets

with the ice pack and the crickets under the

lamps as the “Treatment Crickets,” and the

room temperature crickets as “Control Crickets.”

2. Pass out the ectotherm experiment worksheet.

3. Briefly review the main differences between

reptiles and amphibians using the poster, if

desired.

4. Review what a herpetologist is and inform

them that they will be herpetologists again

today. Pass out the herpetologist badges.

5. Explain that students will be conducting an

experiment to understand how a reptile or

amphibian’s temperature is affected by the

environment.

6. Review the basic steps of the scientific

process: Hypothesis (a proposed explanation

for an observation), Experiment, and Conclu-

sion.

7. Explain how an ectotherm’s (such as a

reptile, amphibian, or cricket) body tempera-

ture changes with the environmental tem-

perature. Have them fill in the ectotherm

definition on their worksheets.

8. Have the students hypothesize how the crick-

ets will move in the cold environment and

the hot environment. Have them write this

hypothesis in complete sentences on their

worksheets.

9. Explain that the treatment groups consist of

crickets whose environments are being

changed. The control group is the group to

which no changes are made.

10. Have the students observe each cricket

group for 30 seconds (begin with control

crickets). Afterwards, have the students

write their observations of how each cricket

group moved. The movements should be

described as: slow, fast, or medium.

UNIT 3 • Reptiles, Amphibians the Scientific Method

11. Ask them to compare what they observed

with what they hypothesized. Have the

students make a general statement as to

how temperature may affect the crickets’

behavior (slow to find food, eaten more

easily, etc.), and write it in the conclusion

section on their experiment worksheet

(in full sentences).

12. Ask the students why they think we used

crickets instead of reptiles or amphibians

(because they are small and easy to manipu-

late, and because they are also ectotherms).

13. Follow up the activity with a discussion

about ectothermy. Discuss a real-world

situation that would apply to the topic. For

instance, ask the students how a cold turtle

might act in the environment, and how this

would affect it (easier to catch, slower

digestion). Explain that although the crickets

are not amphibians and reptiles, they show

how those groups would behave given the

different environmental conditions. Explain

that many times experiments use substitutes

for animals or objects that cannot be used for

research (i.e., for endangered, hard to capture

or handle, hard to care for animals or objects).

UNIT 3 • Reptiles, Amphibians the Scientific Method

Name: _________________________________________________

Ectotherm: ________________________________________________________________________________

________________________________________________________________________________

Hypothesis: ________________________________________________________________________________

________________________________________________________________________________

Observations:

Conclusion: _______________________________________________________________________________

_______________________________________________________________________________

Ectotherm Experiment Worksheet • KEY

Cricket Group Cricket Movement

Control Crickets

Ice Crickets

Hot Crickets

An animal whose temperature changes with the environment’s temperature.

Medium

Slow

Fast

Control Crickets will move more than the Ice Crickets and less than the Hot Crickets.

Ectotherms move slowly in cold environments and fast in hot environments.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Ectotherm Experiment Worksheet

Name: _________________________________________________

Ectotherm: ________________________________________________________________________________

________________________________________________________________________________

Hypothesis: ________________________________________________________________________________

________________________________________________________________________________

Observations:

Conclusion: _______________________________________________________________________________

_______________________________________________________________________________

Cricket Group Cricket Movement

Control Crickets

Ice Crickets

Hot Crickets

UNIT 3 • Reptiles, Amphibians the Scientific Method

Estimated Time 

50-60 minutes

Required Materials

• Teacher Information Packet

• Hot Rock Experiment Worksheet

• Desk clamp lamp with 60-watt light bulb

• Rock (flat, slate, approximately 6–8 inches wide)

• Thermometer

Lesson 3:

Hot Rock

This lesson demonstrates how

ectotherms use the environment to

control their body temperature.

Procedure

1. Set up the hot rock model by first placing the

rock on a table and clamping the desk lamp

above the rock. The lamp should be posi-

tioned so that part of the heat is projected

on the rock, while the rest of the heat is

projected on the table.

2. Review that an ectotherm cannot generate

its own body heat like humans. Instead, they

must utilize objects in their environment and

the heat from the sun to control their body

temperatures.

3. Ask the students to recall the process by which

an ectotherm (such as an amphibian or reptile)

controls its body heat (i.e., thermoregulation).

4. Review that thermoregulation is the process

of an animal using the environment around

it to heat and cool itself to the desired

temperature. When an ectotherm thermo-

regulates, it must move throughout its

habitat to warmer areas to raise its body

temperature, and cooler areas to lower its

body temperature.

5. Pass out the Hot Rock Experiment Worksheet.

6. Remind the students that scientists studying

amphibians and reptiles are herpetologists.

7. Review the basic steps of the scientific

process: Hypothesis (an explanation of

observations), Experiment, and Conclusion.

8. Explain to the students the general procedure

of the experiment: Students observe how

temperature can vary depending on the

exposure to sunlight and the type of surface

that is exposed to the heat. Students use

both touch and a thermometer to observe

these differences.

9. Have the students make a hypothesis about

which object will be the hottest: the air

under the lamp, the top of the rock, the

underside of the rock, or the surface next to

the rock (not under the rock).

10. Check temperatures starting from the cold-

est spot to the hottest. This will allow the

thermometer to record temperatures at a

faster rate. Lift and record a temperature

from directly underneath the rock. Have the

students take the temperature of the surface

next to the rock, then the temperature of the

air, and then the temperature on the top of

the rock. Before you move the thermometer,

record the temperature for each location.

Also, have the students touch all four spots

where a temperature was taken to feel the

temperature of each location.

11. Complete the lesson with a discussion of the

activity. Draw conclusions about the experi-

ment based on the observations recorded.

Discuss how temperatures of objects in the

environment may be affected by their colors or

by the materials of which they are made. Ask

the students to list the objects from coldest to

hottest. Create real-world situations based on

the observations. For example, if a lizard woke

up on a cold morning, where would it most

likely go in order to warm up? If it became too

hot, where might it go to cool down?

UNIT 3 • Reptiles, Amphibians the Scientific Method

Name: _________________________________________________

Hypothesis: ________________________________________________________________________________

________________________________________________________________________________

Conclusion: _______________________________________________________________________________

_______________________________________________________________________________

Hot Rock Experiment Worksheet • KEY

Air

Surface Next

to Rock

On Rock Under Rock

Temperature (F)

The temperature on the rock will be the hottest.

Discuss how an animal in the wild may use these different objects to regulate its temperature.

An option may be to create a real-world situation about a rock, or perhaps create a story

about animals using rocks to regulate temperature.

UNIT 3 • Reptiles, Amphibians the Scientific Method

Name: _________________________________________________

Hypothesis: ________________________________________________________________________________

________________________________________________________________________________

Conclusion: _______________________________________________________________________________

_______________________________________________________________________________

Hot Rock Experiment Worksheet

Air

Surface Next

to Rock

On Rock Under Rock

Temperature (F)