Speciation (Chapters 21-22)

Simulation Activity

1.1 Section Title

Simulation Activity

To get started, click on the "Simulation" button at the top of the map. Select the severity of different mutations and the size of the two daughter populations, then click "Start" to see frequencies change over time. After you've tried the simulation at least once, click the button below to answer questions showing that you’ve understood the concepts covered here.

Simulation Assessment

You must try the simulation before answering the questions.

Simulation Assessment

Question 1 of 10

Questions

Question 1.1

Click on the "Simulation" button at the top of the interactive figure to switch over to the simulation review. Click "Start" and run the simulation until the parent population splits in two. Click "Stop", reset the simulation, and try again 4 more times.

The parent population often has a frequency of 100% grey individuals. How does this differ from a “natural” population?

A natural parental population will have variation.

A natural parental population will include individuals of many species.

A natural parental population will be larger.

A natural parental population does not exist.

Correct.

Incorrect.

Try again.

Question 1.2

Examine the snapshot below of five generations from a sample simulation run.

How is it possible that the green and red phenotype have simply appeared from nowhere in generations 85 and 86 on the snapshot above?

Mutation gave rise to the phenotypes so they appear in the next generation.

The simulation only allows for two possible phenotypes at any one time in the population.

Natural selection caused the population to develop the red phenotype because it is advantageous.

Natural selection is acting against the grey phenotype and is selecting for the other possible phenotypes in the simulation.

Correct.

Incorrect.

Try again.

Question 1.3

Using the following settings, run the simulation four times for 100 generations each:

Population size: 50 on both daughter populations
Mutations: set all mutant phenotypes on both daughter populations to neutral (except for the black phenotype, which is deleterious by default)

Take note of the frequencies of the different phenotypes present in each daughter population at the end of each run of 100 generations. How many simulations resulted in the final phenotype frequencies being the same between the left and right panel?

All of the simulations had the same phenotype frequencies.

Half of the simulations had the same phenotype frequencies.

Less than half had the same phenotype frequencies.

None of the simulations had the same phenotype frequencies.

Correct.

Incorrect.

Try again.

Question 1.4

Which evolutionary mechanism most likely contributed to the pattern you reported in the previous question?

gene flow

natural selection

sexual selection

genetic drift

Correct.

Incorrect.

Try again.

Question 1.5

Using the following settings, run the simulation four times for 100 generations each:

Population size: 50 for the left-hand daughter population, 600 for the right-hand daughter population
Mutations: for both daughter populations, set the grey mutant phenotype as neutral, the green and blue mutant phenotypes as highly deleterious (the top-most radio button), and the red mutant phenotype as highly advantageous (the bottom-most radio button)

Which population has a mutation that reached fixation more quickly than the other population?

the population on the left

the population on the right

It varied over the four iterations of the simulation.

Correct.

Incorrect.

Try again.

Question 1.6

Given the same settings as in the previous question (population sizes of 50 on the left and 600 on the right, grey mutants set to neutral, green and blue mutations set to highly deleterious, and red mutant set to highly advantageous for both populations), why doesn’t the small population reach fixation of the red phenotype more quickly than the large population every time the simulation is run?

Natural selection is not genetic drift. Natural selection operates without respect to population size.

Because natural selection requires variation in order to produce adaptation in a population, if the red phenotype is fixed, natural selection would have no purpose.

Natural selection acts on the population. The red phenotype will become fixed randomly in any population because of drift.

Natural selection will cause fixation quickly in a large population if it is sexual selection. The red phenotype must be correlated with mate choice.

Correct.

Incorrect.

Try again.

Question 1.7

Examine the snapshot below of five generations from a sample simulation run (the simulation was run with different settings than in the previous question).

Just by looking at the frequency pattern above, can you determine whether the high frequency of the red phenotype is caused by natural selection or by drift? Why or why not?

Yes, because only natural selection can result in and maintain such a high frequency of the red phenotype.

Yes, because only drift can result in and maintain such a high frequency of the red phenotype.

No, because drift can cause fixation through random processes. Natural selection could produce this result if the red phenotype was advantageous.

No, because the black phenotype appears in generation 78, so it must remain in the population at low frequency.

Correct.

Incorrect.

Try again.

Question 1.8

Examine the snapshot below from a portion of a sample run of the simulation (the simulation was run with different settings than in the previous question).

If fixation of an allele means it reaches a frequency of 1.0, then how can the appearance of the black phenotype in generation 97 be explained?

The black phenotype was selected for in that generation.

There must have been two heterozygotes in generation 91.

A mutation must have occurred in an individual of the population.

For some individuals a black phenotype was advantageous.

Correct.

Incorrect.

Try again.

Question 1.9

Below is a data table for three runs of the simulation. Final allele frequencies based on phenotypes are given for the left-hand (L) daughter population and right-hand (R) daughter population.

By examining the final allele frequencies of Runs 1 and 2 can you determine whether the L and R populations are now different species?

Yes, the allele frequencies are so different that there has been enough genetic divergence for speciation to occur.

Yes, they are different species because the R population has twice as many phenotypes as the L population.

No, the ability of the R and L populations to interbreed has to be assessed before they can be called separate species.

No, because neither population has changed that much from the initial population.

Correct.

Incorrect.

Try again.

Question 1.10

Below is a data table for three runs of the simulation. Final allele frequencies based on phenotypes are given for the left-hand (L) daughter population and right-hand (R) daughter population.

Examine the final allele frequencies for the R and L populations in Run 3. Assume the two populations are ecologically separated and do not interbreed. Has evolution occurred in these populations?

Yes, because they are reproductively isolated.

Yes, because there has been a change in allele frequencies from the initial population.

Yes, because 3/5 of the phenotypes have the same frequency.

Yes, because one of the phenotypes has been eliminated from the population.

Correct.

Incorrect.

Try again.

Chapter 1. Speciation (Chapters 21-22)

1.1 Section Title

Questions

Question 1.1

Question 1.2

Question 1.3

Question 1.4

Question 1.5

Question 1.6

Question 1.7

Question 1.8

Question 1.9

Question 1.10