Difference between revisions of "PhET-Simulations-for-Biology/C3/Natural-Selection/English-timed"

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Latest revision as of 18:42, 10 August 2022

Time Narration
00:01 Welcome to this tutorial on Natural Selection, an interactive PhET simulation.
00:08 In this tutorial, we will demonstrate Natural Selection, an interactive PhET simulation.
00:17 Here, I am using: Ubuntu Linux Operating System version 16.04,
00:26 Java version 1.8.0,
00:30 Firefox Web Browser version 60.0.2.
00:35 Learners should be familiar with biology and ecology.
00:41 Using this simulation, we will look at a population of rabbits for effects:

Of mutations and selection factors,

00:52 Of environment,

On pedigree.

00:55 Let us begin.
00:58 Mutations-

Mutations are alterations in the nucleotide sequence of any genetic element.

They are passed onto offspring.

01:11 Mutations may or may not change the observable traits or phenotype of an organism.
01:18 Inheritance of mutations can be dominant or recessive.
01:25 Use the given link to download the simulation.
01:30 I have already downloaded the Natural Selection simulation to my Downloads folder.
01:37 To open the jar file, open the terminal. At the terminal prompt, type: cd Downloads and press Enter.
01:48 Type: java space hyphen jar space natural-selection_en.jar.

Press Enter.

02:03 File opens in the browser in 'html' format.
02:08 This is the interface for the Natural Selection simulation.
02:13 Observe the rabbit hopping in the simulation panel.

Click the Pause button at the bottom of the interface.

02:22 Now we will explore the interface.
02:25 The interface has Simulation panel;
02:29 On the left side, Add Mutation,

Edit Genes,

02:35 in the middle- Graph,

Time until next generation progress bar,

02:42 Play/Pause button, Step button,
02:46 on the right side, Selection Factor,

Environment,

Chart.

02:54 Clicking on the Reset All button takes you back to the starting point.
02:59 Let us keep the default settings: None for Selection Factor,

Equator for Environment,

Population for Chart.

03:11 Observe the Population versus Time graph.
03:15 It shows the number of rabbits along the y-axis and time on the x-axis.
03:22 Click Play button at the bottom of the interface.
03:26 In the graph, observe how the black line moves to the right.
03:31 Keep clicking on the Step button to move the simulation along faster.
03:37 If there are no rabbits left, you will see a 'Game Over' pop-up box like this.

The text will read “All of the bunnies died!”

03:48 Click on the Play Again button to resume the simulation.
03:53 Click on Add a Friend to add another rabbit to the simulation.
03:58 Click on Pause at the bottom of the interface.
04:03 Generations of Progeny..
04:06 Observe the labels on the right and Roman numerals on the left of each row.

Generation P is shown in row I (one).

04:17 The F1 generation in row II (two) is made up of the progeny or children of generation P.

And so on until row V (five).

04:30 We will allow the population to grow until F3. This would be three steps after the mating pair.
04:41 Click Play at the bottom of the interface.
04:45 Note how the progress bar is full when a new generation begins.
04:52 The progress bar starts moving to the left as a generation starts growing.
04:58 Click Pause button.
05:01 Click the second button at the top left corner of the graph to zoom out.
05:08 You can now see the height of the next step.
05:12 The black line shows the total number of rabbits in the graph.
05:17 Under Selection Factor, click the 'Food' radio button.
05:22 Under Add Mutation, click the Long Teeth button.
05:27 A text-box “Mutation coming” appears at the bottom of the simulation panel.
05:33 Note the yellow triangle with the lightning inside.
05:37 This indicates a mutation. You can see a picture of long teeth in the text-box.
05:45 Under Edit Genes, the rows next to the Teeth label have become active.
05:52 The radio-buttons can now be clicked.
05:56 For each row, two options appear under the Dominant and Recessive columns.
06:03 To the left of each row, are the pictures of long and short teeth.
06:09 Default selections are dominant mutation for long teeth and recessive for short teeth.
06:17 Observe the progress bar and the graph after the mutation has been added.
06:22 Let us allow the population to grow for another three generations after the mutation.

Keep clicking on the Step button.

06:33 The interval between two narrow steps in the graph corresponds to a generation.
06:41 Click on the second Zoom Out button in the graph until you see the steps.
06:47 Observe how differently coloured lines appear in the graph after mutation and food selection.
06:56 Note that the timing of mutations and selection factors will affect population growth.
07:03 The legend below the graph gives the different colours and what they mean.
07:09 We introduced a dominant mutation for long teeth.
07:14 Let us look at the magenta line for long teeth, the olive line for short teeth.
07:23 Initially, the olive line is above the magenta line.

The number of short-toothed rabbits is higher than that of the long-toothed rabbits.

07:36 Later, the magenta line is above the olive line.
07:41 The number of long-toothed rabbits has increased relative to the short-toothed ones.
07:49 This means that long teeth help rabbits survive by eating the available food.
07:57 Fur Mutation: Set up conditions to study effects of a fur mutation on survival of rabbits.
08:06 Keep brown fur as the dominant mutation and white fur as the recessive mutation.
08:13 Choose wolves as the selection factor.
08:17 Allow the population to grow for another 3 generations after the mutation.
08:25 Observe how the wolves move in and out, killing the rabbits.
08:31 Brown rabbits begin to appear after the mutation was introduced.
08:37 Note that we are still looking at effects of the dominant long teeth mutation besides brown fur.
08:46 Compare numbers of rabbits having white and brown fur in the graph and simulation panel.
08:55 Initially, there are more white rabbits than brown rabbits.
09:02 Later, the number of brown rabbits has increased relative to white ones.
09:10 At the equator, with wolves killing the rabbits, brown fur is an advantage for survival.
09:18 This strategy to blend with the environment is called camouflage.
09:24 What can you say about the numbers of long and short-toothed rabbits?
09:31 Sometimes a mutation changes the phenotype of all rabbits.
09:37 If so, the graph will not compare the mutation versus the wild type (unmutated) phenotypes.
09:45 Here, there are more long-toothed rabbits than short-toothed ones.
09:53 Tail Mutation-

Set up conditions to study effects of a tail mutation on survival of rabbits.

10:02 Keep long tail as the dominant mutation and short tail as the recessive mutation.
10:09 Choose wolves as the selection factor.
10:13 Allow the population to grow for another 3 generations after the mutation.
10:20 Keep clicking on the Step button to move the simulation along faster.
10:28 Click on the 2nd Zoom Out button.
10:31 Note the number of rabbits with brown fur, long teeth and short tails.
10:38 It is higher than that of rabbits with white fur, short teeth and long tails.
10:49 Brown fur and short tails help escape from wolves.
10:55 Long teeth help survival by making it easier to eat vegetation.
11:01 Under Chart, click Pedigree.
11:04 Note the text, “Click a Bunny” at the top.
11:08 Let us click on the rabbit at the left bottom corner of the simulation panel.
11:16 Observe how the selected rabbit is framed inside a blue rectangle.
11:22 The pedigree chart appears for the rabbit framed in the blue rectangle.
11:28 Click on the top right button in the Pedigree window.
11:33 The Pedigree window is separated and the Population chart appears behind it.
11:41 We can now resize the Pedigree window.
11:46 Note the color of the previous four generations of rabbits above the selected rabbit.
11:54 Red crosses on the rabbits indicate that they are dead.
11:59 The yellow triangle with the lightning symbol inside indicates a mutation.
12:06 It shows that that rabbit underwent a mutation; so its genotype and phenotype changed.
12:14 Pedigree analysis allows study of inheritance of genes based on data about phenotypes.
12:23 Click repeatedly on the Step button.

Rabbits can be seen all over the continents on the planet Earth.

12:33 Observe the caption, “Bunnies have taken over the world!”
12:38 These are the long-term effects of the simulation under these conditions.
12:44 Do refer to Additional material provided with this tutorial.
12:50 Let us summarize.
12:52 In this tutorial, we have demonstrated how to use the Natural Selection PhET simulation.
13:00 Using this simulation, we looked at a population of rabbits for effects:

Of mutations and selection factors,

Of environment,

On pedigree.

13:13 As an assignment-

observe the rabbits: for effects of mutations and selection factors in Arctic environment.

13:23 After switching mutations from dominant to recessive and vice versa.

For changes in pedigree, under different conditions.

13:34 The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

13:43 The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates on passing online tests.

For more details, please write to us.

13:55 Please post your timed queries in this forum.
13:59 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
14:08 Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.

14:21 This is Vidhya Iyer from IIT Bombay, signing off.

Thank you for joining.

Contributors and Content Editors

Nancyvarkey, PoojaMoolya, Sandhya.np14

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