Preview - Evolution Of Populations To Speciation (Advanced)

Test Your Predictions

Set the initial values to:

Setting

Value 

CHANCE-FLOWER-TIME-MUTATION 

10%

CHANCE-TOLERANCE-MUTATION

10%

INITIAL-TOLERANCE 

all no tolerance

VISUALIZE-TIME-STEPS

“days” or “years” 

(you may switch back and forth as the model is running)

  1. Press SETUP. and Press GO/STOP to run the model.Keep the model running until the SIMULTANEOUS FLOWERING graph shows that the number of simultaneously flowering plants in the contaminated soil and in the regular soil, is very close to zero.

  2. Now make sure you have switched back VISUALIZE-TIME-STEPS to “days” mode and keep the model running.Below, record what you notice about when the flowers on the left side of the ecosystem are blooming versus the flowers on the right side of the ecosystem.

In the next set of questions you will try to explain why the flowers on the right have a different flower time than those on the left.  To do this you may want to rerun this previous exploration in “days” mode, change labels, and study the model graphs.  Feel free to conduct new experiments in this exploration to help you understand and explain why the initial plant population has “speciated”.

Referenced Questions

These questions were answered in the previous steps. They are provided here for your reference.

What do you predict the outcome will be for the metal tolerance of the plants?

What do you predict the outcome will be for the flower time of the plants?

Questions

Please answer the questions below.

Observations

Why are the tolerance values in the two regions different, and why do you think there aren't there many plants in the population with a tolerance in between 10 and 90?  Think back to the concepts of fitness, natural selection, and adaptation in response to different environments from the previous lessons.

When the plants first reached the blue contaminated soil, the plants growing in that region increased their metal tolerance very quickly.  Do you think this was a result of stabilizing selection or directional selection?  Why?

Now let's think about the differences in flowering times.  If a plant with no metal tolerance, growing on the left side (clean soil) were to reproduce with a plant with metal tolerance growing on the right side (contaminated soil), their offspring would inherit genetic information from both parents. Why would this offspring plant be at a competitive disadvantage for survival compared to other plants growing either in the clean soil or in the contaminated soil?

If a plant has to reproduce with another plant in order to have offspring, why would flowers in metal soil evolve a different average flower time than the flowers in the clean soil?

The type of selection acting on flowering times, where intermediate values are selected against and variation increases, is called disruptive selection.  How is it similar to or different from stabilizing and directional selection?

 

How do the TOLERANCES and FLOWER TIMES graphs support the claim that: "The population of plants on the left side of the ecosystem no longer breed with the population of plants on the right side of the ecosystem"

Do you think that the population of plants on the left side and the population of plants on the right side are still part of the same species?  Why or why not?

Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.