Lizard Evolution Virtual Lab

Lizard Evolution Virtual Lab

The more than 700 islands of the Caribbean are home to about 150 species of anoles, a group of lizards of the genus Anolis.

These lizards live in diverse habitats and vary greatly in size and other physical characteristics, such as leg and tail length and skin color and pattern.

Why are there so many species of anoles? And how did they evolve?

To answer these questions, you will perform several exercises modeled after actual research studies. The lab is divided into four modules, each one involving data collection, calculations,

analysis, and answering questions.

The virtual lab includes four modules that investigate different concepts in evolutionary biology, including adaptation, convergent evolution,

phylogenetic analysis, reproductive isolation, and speciation.

Module 1: Ecomorphs

Species of Caribbean anoles can be categorized into groups, called ecomorphs, according to their body characteristics (morphology) and the ecological niches they occupy. In this

module, you will take measurements of lizards from eight species belonging to different ecomorph groups. (Approximate length: 1 hour and 30 minutes)

Part 1: Lizard Groups

1. How did you originally group the lizards and what labels did

you give the groups? List them below.

Part II: Measuring the Lizards’ Traits Your Measurement Table

A.

everma nni

A.

cristatel lus

A.

occultu s

A.

pulchell us

A.

olssoni A.

coelesti nus

A.

cybotes A.

sheplan i

Hindlim b

Length

A.

everma nni

A.

cristatel lus

A.

occultu s

A.

pulchell us

A.

olssoni A.

coelesti nus

A.

cybotes A.

sheplan i

Hindlim b

Length

Body

Length

Tail

Length

Lamella

e Count

Relative

Hindlim

Body Length Tail Length Lamella e Count

1. How do your table measurements compare to the “reference measurement table”? Were any severely off in comparison? If so, why do you think this happened?

2. Are your calculations similar to the ones in the “reference measurement table”? If not, why do you believe this

happened?

3. Do you notice any patterns in the measurements calculated?

4. What does the term “ecomorph” stand for?

Part III: Results Table + Video

1. What are the four ecomorph groups described in the video?

What characteristic is associated with each particular group?

2. Would you change your original groupings (See Question #1 in Part I) based on this new information from the video and the measurements you took in Part II? If so, why?

Part IV: Graph Your Results

Plotting Toepad vs. Hindlimb Length

*Construct graph (such as the one in the virtual lab) on graphing paper and attach to the back*

Plotting Toepad vs. Hindlimb Length

Relative Hindlimb

Length Lamellae Count Relative Hindlimb

Length Relative Tail Length A. evermanni

A. cristatellus

A. occultus

A. pulchellus

A. olssoni

A. coelestinus

A. cybotes

A. sheplani

A. evermanni A. cristatellus A. occultus A. pulchellus A. olssoni A. coelestinus A. cybotes A. sheplani

*Construct graph (such as the one in the virtual lab) on graphing paper and attach to the back*

1. What is the reason for performing these two comparison charts?

2. After viewing the Reference graphs, how would you reconsider your original groupings of the lizards for each ecomorph?

Part V: Questions

Write your answers for the questions in this section. If you

answered the question incorrectly, explain why that choice was wrong and write the correct answer. If you answered correctly, explain your reasoning for choosing that answer.

1. What do the four groups of anoles (trunk-crown, twig, trunk-

ground, and grass-bush) represent?

2. Which of the following features may differ among different ecomorph groups?

3. Why did you need to calculate relative hindlimb length rather than absolute hindlimb length?

4. Species that belong to the same ecomorph group are similar in

appearance and occupy similar habitats. This suggests that

species living in similar habitats evolved similar traits, which

allow them to be successful in those habitats—in other words,

the different traits are adaptations. Which of the following

observations supports this conclusion?

5. Based on what Dr. Jonathan Losos said, why have different lizard species evolved to occupy different parts of the habitats?

6. On Puerto Rico and Hispaniola, you find the same:

7. Based on what you have learned so far, what is the most likely explanation for why the same ecomorphs evolved on both Puerto Rico and Hispaniola?

Module 2: Phylogeny

Analysis of the DNA sequences of certain genes reveals the evolutionary relationships among different anole species. In this module, you will build a phylogenetic tree of anole species.

(Approximate length: 15 minutes) Part I: Generating a Phylogenetic Tree

Take the DNA sequences and plug them into the MABL website (just as the directions state) and email the results to yourself.

When you receive the email with the link to your phylogenetic tree, forward me the link to my email ([email protected]), so I know you actually did the tree.

1. Do you notice any differences in the tree you constructed versus the example the phylogenetic tree for the 8 species of lizards? If it is different, why do you think this occurred?

Part II: Coloring Tree Branches

Construct two trees (Ecomorphs and Island) below using the same colors as the key used in the lab.

1. What patterns do you notice based on the relation of the eight lizard in regards to ecomorph type and island location?

Part III: Questions

Write your answers for the questions in this section. If you

answered the question incorrectly, explain why that choice was wrong and write the correct answer. If you answered correctly, explain your reasoning for choosing that answer.

1. The tree is more consistent with which of the following hypotheses:

2. Which of the following statements is supported by the evidence from the tree?

3. Which of the following statements is supported by the

evidence from the tree?

4. According to Dr. Losos, the independent evolution of similar species on the different islands is an example of which of the following processes?

Module 3: Experimental Data (Extra Credit)

What happens when lizards that belong to a particular ecomorph group are placed in a different habitat? In this module you will analyze data from an experiment designed to answer that question. (Approximate length: 30 minutes)

Part I: About the Experiment Part II: Taking Measurements

Iron Cay X-Rays

1

Hindlimb Length Tail Length

2 3 4 5 6 7 8 9 10

Iron Cay I X-Rays

1

Hindlimb Length Tail Length

2 3 4 5 6 7 8 9 10

Module 4: Dewlap Colors

No two lizard species living in the same habitat share the same type of dewlap, the flap of skin under their throats that male anoles display to attract females. In this module, you will

characterize two species of lizards based on their dewlap color.

(Approximate length: 15 minutes) Part I: Introduction

*Watch the video*

Part II: Measure Dewlaps

A. cristatellus

Individual Dewlap Color Mean Calculations Mean:

SD:

SEM:

A. cooki

Individual Dewlap Color Mean Calculations Mean:

SD:

SEM:

1. How your calculations compare to the reference table? Do you see any trends?

Part III: Results Graphs

*Construct graph (such as the one in the virtual lab) on graphing paper and attach to the back. Make sure everything is labeled*

1. Does your graph coincide with the graph generated by a scientist using the same data set? If not, why?

Part IV: Questions

Write your answers for the questions in this section. If you

answered the question incorrectly, explain why that choice was

wrong and write the correct answer. If you answered correctly,

explain your reasoning for choosing that answer.

1. Which anole species has a brighter dewlap?

2. Male anoles use their dewlaps to communicate and to attract females of their own species. What is an adaptive explanation for why the dewlap of one species evolved to be brighter and that of another species darker?

3. According to Dr. Losos, dewlap color is an adaptation to:

4. The population of Anolis cristatellus that you analyzed lives in a shady, forest environment and A. cooki in an open, sunny environment. Are the results you obtained consistent with what Dr. Losos describes?

5. A. cristatellus and A. cooki are different:

6. No two species of lizards living in the same area have the same dewlap color. The different dewlaps keep species:

Summary

Using the video summary, graphs, charts, and questions,

summarize what you learned in this lab.