Download Simulation 1: Evolution by Natural Selection

Ecology Lab
name: _____________________________
Lab 5: Natural selection – the mechanism of adaptive evolution
Charles Darwin’s great contribution to the field of biology was figuring out the process by
which adaptations evolve. This process is natural selection. We will use a computer simulation called
“EvoDots”* to explore how natural selection, and how it leads to adaptation.
In the EvoDots simulation, you can explore how a population of dots evolves. You will play the role of a predator: you
can ‘eat’ a dot by clicking on it. You will also collect data on how the population of dots changes. Click the EvoDots icon
to open the simulation.
Simulation 1: Evolution by Natural Selection
Click ‘New Population’ to generate a population of 50 dots. Before you start ‘eating’ dots, record the number of dots of
each color in the starting population; use the attached data sheet.
Now, click ‘Run’ and the dots will start moving around. Eat 25 dots as quickly as you can! When only 25 dots remain,
click ‘Stop.’ On your data sheet, record the number of dots of each color remaining after predation.
What are two ways that the dots vary?
1)
2)
Which dots are easier to catch?
Click ‘Reproduce’ and each of the 25 remaining dots will split into 2 dots (this is an example of asexual reproduction).
Now, record the number of dots of each color in the population after reproduction.
What is the relationship between the phenotype of the ‘mother’ dot and her ‘daughter’ dots?
Run through several more generations, ‘eating’ 25 dots from each generation, then allowing the survivors to reproduce. Be
sure to record the data for each generation.
Enter your data into a Microsoft Excel spreadsheet and create a graph that shows the frequency of dots of each phenotype in
each generation.
Has your population evolved? Why or why not?
Has your population undergone adaptive evolution? Why or why not?
Does you population still have the potential to evolve? Why or why not?
* EvoDots 1.0 Copyright 2001 by Jon C. Herron
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Ecology Lab 5 – Natural selection in EvoDots
name: _____________________________
Simulation 2: The Requirements of Natural Selection
Can a population evolve if all members of the population are identical? Why or why not?
You can explore this question in “EvoDots” by unselecting the ‘Variable’ box. Then click ‘New Population.’
What does this new population look like?
Click ‘Run,’ and go through a few rounds of predation (eating 25 dots each time) and reproduction. Record the data on
your data sheet. When you’re finished, reselect ‘Variable.’
Has this population evolved? Why or why not?
Does this population have the potential to evolve? Why or why not?
Can a population evolve if offspring do not resemble their parents? Why or why not?
Explore the role of heritability by unselecting the ‘Heritable’ box. Get a new population and go through one generation of
predation and reproduction. Record the data!
What is the relationship between the phenotype of the ‘mother’ dot and her ‘daughter’ dots in
this population?
Go through several more generations of predation and reproduction. Record the data on your data sheet. When you’re
finished, reselect ‘Heritable.’
Enter your data into a Microsoft Excel spreadsheet and create a graph that shows the frequency of dots of each phenotype in
each generation.
Has this population evolved? Why or why not?
Has this population undergone adaptive evolution? Why or why not?
Can a population evolve if survival is random? Why or why not?
Explore the role of selective survival by unselecting the ‘Selective’ box. Get a new population and go through one
generation of predation and reproduction. Record the data.
What happens when you try to ‘eat’ a dot?
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Ecology Lab 5 – Natural selection in EvoDots
name: _____________________________
Go through several more generations of random removal of 25 dots followed by reproduction. Record the data.
Enter your data into a Microsoft Excel spreadsheet and create a graph that shows the frequency of dots of each phenotype in
each generation.
Has this population evolved? Why or why not?
Has this population undergone adaptive evolution? Why or why not?
Charles Darwin’s theory of evolution by natural selection states:
if a population contains variation,
and if the variation is at least partly heritable,
and if more offspring are born than will survive to reproduce,
and if survival is selective,
then the population will evolve by natural selection. Evolution by natural selection is adaptive
because it results in later generations in which typical individuals are better suited to survive
(or reproduce) in their environment than the typical individuals in early generations.
Simulation 3: The Role of Mutation
Click ‘Window’ in the toolbar and scroll down to ‘Mutation’s Role.’ Generate a new population and select ‘with
mutation.’ Go through several generations of predation and reproduction. Record your data.
Enter your data into a Microsoft Excel spreadsheet and create a graph that shows the frequency of dots of each phenotype in
each generation.
Could you detect mutations in this population? What did they look like?
Why is mutation important?
Other questions to explore:
What is the effect of changing selection intensity? For example, instead of removing 25 individuals,
you could remove 37 or 38 (then reproduce twice to get the population back up to near 50).
What is the effect of changing population size? In the ‘Mutation’s Role’ window, you can select the
beginning population size. Warning: Don’t try to go larger than 50, or the program may crash!
Use EvoDots to explore one of these questions or one of your own. Below, describe what
happened and what you learned.
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