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February 2015
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Student Handout
Virtual Lab
Lizard Evolution Virtual Lab
LIZARD EVOLUTION VIRTUAL LAB
Answer the following questions as you finish each module of the virtual lab or as a final assessment
after completing the entire virtual lab.
Modul
e 1: Ecomorphs
1. At the beginning of the virtual lab, you were asked to sort eight lizards into categories. What
criteria did you initially use to make your groups? Did you revise your criteria later? Why?
2. An adaptation is a structure or function that is common in a population because it enhances the
ability to survive and reproduce in a particular environment. Provide one example and an
explanation of one adaptation in the Anolis lizards.
3. Provide one evolutionary explanation for why lizards living in the same part of the habitat (i.e.,
grass) would have similar characteristics.
4. What is an ecomorph? Provide one example from the virtual lab.
5. How is an ecomorph different from a species?
6. Explain how a particular body feature of one of the lizard ecomorphs from the virtual lab is an
adaptation to their particular niche.
I based my criteria on the size of the anoles' legs. I did not revise my criteria later. I
chose the size of the anoles' legs because I believe that each of the different anoles had
evolved based on their habitat, and I wanted to base my experiment on that.
One adaptation is the short legs on the sheplani hispaniola anolis lizard. This is most
likely due to the slim branch it lives on. The short legs make the lizard able to hold onto
the branch/twig better and survive longer because it does not fall off.
Lizards in the same habitat would have similar characteristics because there are many
ways to do something, however there is only one way that is the best for surviving.
Basically, lizards in the same habitat have the characteristics that are most fit for
survival, so most lizards in that habitat would exhibit those most fit characteristics.
Ecomorphs are species with similar body types and habitats. "eco" stands for ecological
niche and "morph" for morphology, or shape. An example is how the sheplani
Hispaniola and occultus Puerto Rico lizards both have short legs, but with slight
differences/look.
An ecomorph is different from a species because it only classifies the organism as
having similar body types and habitats, however species have other different
characteristics such as color or look.
One of the lizard ecomorphs, the occultus Puerto Rico anole has short legs because it
needs to be able to stick to/crawl on slim twigs in their habitat.
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February 2015
Page 2 of 5
Student Handout
Virtual Lab
Lizard Evolution Virtual Lab
Module 2: Phylogeny
1. In module 1, you identified which species of lizards were most similar to one another based on
relative limb length and toe pad size. In this module, you determined which lizards are more
similar to one another based on what type of information?
2. Are the species of lizard that are more similar to one another according to body type also more
closely related based on the results obtained in this module? Explain your answer.
3. The figures below show two phylogenetic trees similar to the one you constructed in the virtual
lab but with more lizards. The trees below show the evolutionary relationships among species
from four ecomorphs from the four largest Caribbean islands.
Figure 1. Phylogeny of anole lizards on four
of the major Caribbean islands color-coded
according to geographical distribution. Light
dotted line, Puerto Rico; small dashed line,
Cuba; large dashed line, Hispaniola; and solid
line, Jamaica.
Figure 2. Phylogeny of anole lizards in the
four major Caribbean islands colored in
according to ecomorph. Light dotted line,
twig; small dashed line, trunk-ground; large
dashed line, trunk-crown; solid line, grass-
bus.
I determined which lizards are more similar based on DNA sequence analysis.
No, lizards that are similar according to body type are not more closely related based on
the results obtained from the DNA sequence analysis. This is because similar body
types are farther away from each other on the phylogeny tree.
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February 2015
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Student Handout
Virtual Lab
Lizard Evolution Virtual Lab
What conclusion can you draw about the evolution of the Anolis lizards based on these figures?
4. What is convergent evolution? Use evidence from the trees to explain how the Anolis lizards are
an example of this concept.
Modul
e 3: Experimental Data
1. In Dr. Losos’s experiment, why was it important that the experimental islands lacked lizards?
2. Dr. Losos’s data suggest that after only a few generations, the lizards on the experimental
islands have shorter legs on average than the lizards on the larger island. Explain how the data
you collected either supports or does not support this claim.
3. Based on what you know about the experimental islands and the lizards that were placed on
these islands, explain how and why the average leg length of the population might change over
time. Include the concept of natural selection in your discussion.
4. If the population from one of the experimental islands were reintroduced on the original island,
do you predict that lizards from the two populations would still mate and reproduce? Justify
your answer with scientific arguments.
The conclusion I can draw about the evolution of the Anolis lizards is based on
ecological niches on an island rather than the entire island itself. Two anoles on
different islands can have similar traits as long as their ecological niches are similar.
Convergent evolution is where organisms that aren't closely related independently
evolve and have similar traits due to similar environments or ecological niches. The
phylogenetic trees show this type of evolution because similar traits are based on
environments, and not location/species type. For example, anolis cybotes and anolis
sagrei both are trunk ground anoles, but live on different islands.
It was important because it allowed each ecomorph to be isolated and easier to study
their evolutions.
The data I collected supported Dr. Losos's claim because it shows that because the
environment on the island was more suited for shorter legs, the lizards evolved to have
shorter legs. Ecomorphs are based on ancestral causes, not geological
location/isolation, so the anoles evolved with shorter legs because shorter legs
increased their chances of survival.
I believe that the average leg length of the population will shrink because of the
environment/ecological niches of the experimental island. Because the advantage of
longer legs has been lost, some of the anoles will evolve with shorter legs, and some
will not. The ones with shorter legs will survive better and the ones with longer legs will
survive worse/die off. Therefore, in the end anoles with shorter legs will dominate the
population. This process is called natural selection.
I believe that the lizards from the two populations, both short legged and long legged
will still mate and reproduce. First of all, the lizards are still of the same species.
Secondly, the lizards would mate and reproduce because it will increase their species
chances of survival. In general, any chance of increasing survival rates will be taken in
any natural circumstance.
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February 2015
Page 4 of 5
Student Handout
Virtual Lab
Lizard Evolution Virtual Lab
Module 4: Dewlap Colors
1. Anolis cristatellus and A. cooki are both trunk-ground anoles that live on Puerto Rico. A.
cristatellus lives in a shady, forest environment, while A. cooki lives in an open, sunny
environment. What is an adaptive explanation for why the dewlap of one species evolved to be
brighter and that of another species darker?
2. From the bar graph generated in the virtual lab (see below), how do the dewlap colors of the
two species compare?
3. Ho
w would you determine whether the difference between the two populations is statistically
significant?
4. If a species of anoles with dark dewlaps colonized a heavily forested island, predict what would
happen over time to the color of the dewlap. Using your knowledge of natural selection and
genetics, explain your prediction.
The anolis cristatellus has a brighter dewlap and the anolis cristatellus has a darker
dewlap. Their dewlap contrasts the brightness of their environment, most likely because
it stands out more and attracts more female anoles.
The anolis cristatellus has a brighter dewlap by +2.3 and the anolis cooki has a darker
dewlap by -2.3.
There is definitely a difference between the two populations because their bars in the
graph both have different lengths +/- 2.3.
Over time, the color of the anoles' dewlaps would brighten because of their adaption to
the environment. This adaptation would allow more reproduction which would increase
survival rates/chances.
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February 2015
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Student Handout
Virtual Lab
Lizard Evolution Virtual Lab
Extension Questions
1. To m
inimize interspecific competition, organisms often divide the limited available resources in
an area, a concept called “resource partitioning.” As an example of this concept, the figure
below illustrates how different species of warblers utilize different portions of an individual tree.
Figur
e 3. Different species of North
American warblers live in different
parts of the same trees. The
shaded areas indicate the habitats
each warbler species occupies.
Explain how the different species of anoles on an island demonstrate “resource partitioning”
similar to the warblers in the figure.
3. Explain how resource partitioning can promote long-term coexistence of competing species,
thus increasing biodiversity.
Different species of anoles on an island would demonstrate "resource patitioning" by
seperating to different geological niches on the island. For example, anoles with short
legs would move to where there are slim twigs and anoles with long legs would either
live high up in trees or on the ground. In addition, anoles with brighter dewlaps would be
in darker areas and anoles with darker dewlaps would be in brighter areas.
Resource partitioning can promote long-term coexistence of competing species
because it allows different competing species to live in an area that suits their own
survival needs. Two species do not have to compete for the same space if they have
different traits because if they separate, then they have a better chance of survival. This
increases biodiversity because as long as there is varying habitats and geological
niches, then species can live separate from each other and have diversity. Contrary, if
there was only one type of habitat possible of living in, then the species would have to
compete for that land and the most fit would win. This would then mean that only one
species would survive in that habitat.
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