• Evolution
     
    Big Idea
     
    The genes and traits of populations change over time. 
     
    Essential Questions 
    1. Why do populations need genetic variation to evolve?
    2. How can fossils teach us about the history of life on Earth?
     
    Bill Nye Populations

     

    You did it! You finished the genetics unit, but don't think you can just forget it! In our evolution unit, we'll be using everything we learned in genetics about DNA, mutations, cell division, and reproduction. This time, though, we won't just be looking at individual animals and plants, we'll be looking at entire populations of them! What's a population? Well, we have our guest teacher, Bill Nye, here to tell you all about it.

    Before you watch, tape the Bill Nye Populations worksheetView in a new window into your notebook and answer the "Before You Watch" questions. Then take notes as you watch. When you're done answer the "After You Watch" questions.

    Bill Nye Populations (Links to an external site.)Evolution

     
    PBS Dog Breeding Game
     
    You've seen chihuahuas, bulldogs, and labradors, but have you ever wondered how people can create dog breeds like that? In this activity, you will become a dog breeder. You can control the offspring's traits by carefully selecting the parents! Use what you know about dominant and recessive traits as well as punnet squares to help you choose the parents that will give your puppies the traits you want. Begin with Level 1. Record your data on your worksheet as you go. 
     
    Dogs & More Dogs
     
    200,000 years ago, man's best friend didn't exist! What did those poor cave men and women do? Who fetched the newspaper back then? 
     
    So if poodles, labradors, and chihuahuas didn't exist, where did they come from? Watch the video, "Dogs & More Dogs" by NOVA, to find out. 
     
     
    Population Genetics Game
     
    Can the traits of a population really change over time? Let's find out! We're going to start with a population of mice that have been accidentally released into White Sands National Monument. Some of the mice are brown, and some are white. Unlike in their safe, little cage, there are predators here in the park. Will this change the genes that the population has?
     
    Working with your group, use a game set to model what happens to the mice. Before beginning the game, make a pie chart of the number of brown and white alleles in the population. When you are done, make another pie chart. Is there a difference? Why do you think that is? Record your data and answers in your game booklet in your notebook.
     
     
    Percents
     
    To analyze our data from our Population Genetics game, we are going to calculate what percent of alleles in our last generation that are brown and what percent are white. What is a percent? It's a combination of per and cent. That's what you were going to say, right? No, really! It is! Per means "for each." That means when you drive 50 miles per hour, you are going 50 miles for each hour you drive, and if you get 15 pickles/jar, you get 15 pickles for every jar. Cent means "100." that's how many cents are in a dollar. It's also the number of years in a century. (How many soldiers do you think served under a Roman Centurion?) So if per means "for every," and cent means "100,"  percent means "for each hundred." Percents are a proportion related to 100! So if 1/2 of MacArthur students prefer pizza to hot dogs, that is the same as 50/100. For every 100 students, 50 of them prefer pizza! 
     
    How are percents and fractions related? How do you change a fraction to a decimal or a percent? (You'll need to know this to finish your population genetics lab.) First, watch the BrainPOP video on percents; then Check out this tutorial and game on the Dunk Tank at PBS.org. Think you already know how to use percents? Try this Cyberchase game at PBS.org! Another fun game to play is "The Legend of Dick and Dom" from the BBC.
     
     
    Darwin's Theory - Natural Selection
     
    What is evolution? When the traits of a population change over time, that is evolution. In our mouse game, we saw that over 4 generations of living in white sands, the white alleles became more common because white mice camouflaged better. That meant they were more likely to survive and pass on the white trait to the next generation. This process is called natural selection. To summarize how this process works, watch the presentation "Recipe for Evolution." Take notes in your notebook. (To learn more, check out some of the other links on the Variation, Selection, and Time page.)
     
    After traveling to the Galapagos Islands, Charles Darwin first proposed that natural selection is what causes species to evolve. See if you can find the Galapagos islands on Google Maps WITHOUT using the search box. Just zoom out and move the map around; then zoom in on the right area to find them. They are about 600 miles off the west coast of Ecuador. (Hints: Ecuador is along the north-western coast of South America. The largest of the Galapagos islands is called Isla Isabella.) Watch the National Geographic video "Galapagos Islands," to see some of the amazing wildlife that Darwin saw.
     
    Read about Charles Darwin in on pages 150-151 in your Interactive Reader (306-307 in your text book). In your notebook, answer the following questions based on the reading:
     
    1. What did Darwin notice about the wildlife on the Gallapagos Islands? (Give specific examples.)
    2. What question did Darwin wonder about after observing the Galapagos Islands' wildlife? 
    We will use this information in the introduction to our essay about how Darwin developed his theory of evolution by natural selection.

    Darwin's Theory - Selective Breeding
     
    Focus Question: What lesson did Darwin learn from selective breeding?
     
    We will be writing a paragraph about this in our essay about how Darwin developed his theory of Evolution by Natural Selection. To begin, in your Interactive Reader page 152 (text p. 308), read the section called "Ideas About Breeding." 
    1. Topic Sentence: Find the sentence that best answers the question. Underline it in your Interactive Reader (not the text). Paraphrase this sentence. It will be the topic sentence for your paragraph.
    2. Elaborate by defining "selective breeding" in your own words. Use your notes from "Dogs and More Dogs" and the dog breeding game to help you.
    3. Elaborate by giving two examples of how the traits of an entire population can change over time through selective breeding. You may use one example from the "Dogs and More Dogs" video and one from your choice of the sources below. In each example, explain:
      • What plant or animal people were selectively breeding 
      • Which trait they wanted, and
      • What happened to that population's traits over time.
    Read or watch one of the sources below to find more examples of traits spreading through a population by selective breeding:
    Darwin's Theory - Thomas Malthus
     
    Focus Question: What did Darwin Learn form Thomas Malthus?

    Use an egg carton to model Thomas Malthus' ideas about population. There are 2 rows of 6 egg cups. Place the carton horizontally, so there is a "top" and "bottom" row. In the top row, we will place pinto beans to represent the human population. In the bottom row, we will put black beans to represent the food for the people.

    1 pinto bean = 100 people
    1 black bean = food for 100 people for life

    Copy the following data table under the question:

     Generation 1 2 3 4 5 6
     
     People
    (Pintos) x2
     
     Born:
     
    Survivors: 
     
     Born:
     
    Survivors: 
     
     Born:
     
    Survivors:
     
     Born:
     
    Survivors:
     
     Born:
     
    Survivors:
     
     Born:
     
    Survivors:
     
     Food
    Supplies
    (black
    beans)
    +1 
         

    Rules:
    1-In the first generation, start with two people and two food supplies. 
    2-The people who have enough food survive; the ones that don't starve. So if you have 7 people and 4 food supplies, then only 4 people survive, and 3 people starve.
    3-Only the survivors reproduce. Each survivor has 2 children; so If 4 people survive, in the next generation there will be 8 people born (4 people x 2 = 8 people).
    4-In each generation, the food supply increases by 1, so the 2nd generation will have 3 food supplies (2 food supplies + 1 = 3 food supplies).
    5-After each generation, record your data in your chart.
    6-Graph your data. The X axis should be "Generations," and the Y axis should be "Number of people and food supplies." Make 2 lines on your graph. One will be the number of people (graph both the number of people born and the number of survivors.); the other line will be the number of food supplies.
    7-Notice how the population increases and decreases. Not all the people born survive. Also notice that the population always goes down to the level of the food supply. The population may go over it for a time, but it must come back down. Since food supply limits how large the population can get, we call it a limiting factor. 
     
    Read more about this in the section on called "Ideas About Population" (IR p.153, text p. 309). Use what you learned from that paragraph and your model to answer the question "What did Darwin learn from Thomas Malthus?" 
    From Malthus, Darwin learned ....   Based on this, Darwin reasoned ... 
     
    Darwin's Theory - Lyell and the Age of the Earth
     
    Focus Question: What did Darwin learn from Charles Lyell? Why was that important to his theory? 
     
    Without the research Lyell published, the theory of Natural Selection would make no sense. Read about Charles Lyell and watch the first 5 minutes of "How the Earth Was Made."** The video doesn't mention Lyell, but the research they are talking about is the same research that he published. When you're done, read the section called "Ideas About Earth's History" in your book (IR p.153, text book p. 309). Use what you learn from these sources to answer the focus questions. This will be your topic sentence(s). Add background information an other details to support your main idea. As always, write in your own words.
      
    **Note: If you were absent, there are 3 ways you can watch the video. This is the 1 1/2 hour special NOT an episode in the series that has the same name.
    1. I have the DVD, which you may watch during tutoring. (Free)
    2. Watch it through Amazon streaming (Find episode 24 on the list SD-$1.99, HD-$2.99)
    3. It's also on iTunes (Find episode 6 on the list $3.99)
     
    Natural Selection Illustration
     
    So what exactly is Darwin's theory? We are going to summarize it by creating an illustration of natural selection. You will be creating an illustration similar to the one on page 310 in your textbook, except that each student will pick a species of wild plant or wild animal that was not used as a sample. Create a rough draft in your notebook (stick drawings are fine here). Then create your final draft on the worksheet provided. This must be accurate, neat, and in color.
     
    In your notebook, divide your page into 4 quadrants. You are going to create an illustration similar to the one on page 310, but change the captions to make sense for your organism. (Ex: Instead of "A tarantula's egg sac may hold 500-1000 eggs," I put "A mallard may lay 6-12 eggs in a nest.")
    • Research accurate information about your organism for the captions.
    • Do NOT use unreliable sources like:
      • Yahoo Answers
      • Wiki Answers
      • Any site that is not created by a professional organization
    • You may use Wikipedia, but choose "Simple English" as the language.
    Quadrant 1 - "Overproduction"
    • Research accurate information about your organism for the captions:
      • How many offspring does your species produce?
      • Use the correct term for the offspring as well. Ex: Kangaroos have joeys. Foxes have kits.
    • Do NOT use unreliable sources like:
      • Yahoo Answers
      • Wiki Answers
      • Any site that is not created by a professional organization
    • You may use Wikipedia, but choose "Simple English" as the language.
    Quadrant 2 - Your illustration must SHOW the differences among the animals or plants.
    • Use labels to show traits that aren't visible like "smarter" or "more aggressive." 
    Quadrant 3 - Struggle to Survive (Selection)
    • Illustrate a true struggle in the wild (no human interference).
    • If your animal is a top predator, you may not put that it "could be eaten by _____." Think of other traits that it might need to outcompete other predators for food like hunting skills, speed, camouflage, etc.
    Quadrant 4 - Successful Reproduction
    • Show that the offspring are similar to the parent. Again, labels are good for traits we can't see.
    HINTS
    Population is limited by competition: 
    The bighorn sheep that wins this fight will get the right to mate with the females and pass on his traits. What traits do you think will help him do that?
     
    Animals compete to mate in other ways too. Sometimes males develop traits that make a female choose him as a mate. (In some species this works the other way around too!) See "Beautiful Plumed Bird of Paradise" by BBC.
     
    Population is also limited by starvation:
    What traits does the cheetah need to catch enough prey to survive and reproduce? Watch "Predator Cheetach vs. Antelope" by National Geographic to find out.
     
    Population is limited by resources like water:
    What traits do springbok antelope have that help them survive in their environment? ("Springbok Antelopes vs Cheetah" BBC Video
     
     
    How the Earth Was Made
     
    Now we will discover Darwin's next big lesson that helped him develop his theory. In order for natural selection to produce the many species alive on Earth today, there would have to be a very long time, but people believed the Earth only existed as long as humans had existed. In Darwin's time, we were discovering that the Earth was much older that we thought before. Watch the History Channel Special "How the Earth Was Made" to find out what Darwin knew and what we know now. (The full video is available on iTunes if you missed it, or you may watch during tutoring. It's #6 on the list.)
     
     
    Peppered Moth Natural Selection
     
    You know that the organisms with the most favorable traits are the most likely to survive, but what traits are most favorable? That depends on the environment, and the environment can change over time! Read about Peppered Moths and do the simulation to find out what happens when the environment changes. There's one important rule: When you are the predator, don't be a picky eater! You are hungry. Eat the first moth you see, don't choose what color you want to eat.
     
    Answer these questions in your notebook. Answer numbers 1, 2, and 3 BEFORE you begin the simulation. 
    1. What variation exists in the peppered moth population? (Read the section called "Life Cycle of the Peppered Moth" to find out.)
    2. What happened to the peppered moths' environment? (Read the section called "Pollution and Peppered Moths.)
    3. Do a pie chart showing the moth population before you started. (Find this information in the introduction to the simulation, "A Bird's Eye View of Natural Selection.")
    4. Do a pie chart showing the moth population after you did the simulation on white bark.
    5. Do a pie chart showing the moth population after you did the simulation on dark bark.
     
    Darwin's Survival Game "Who Wants to Live a Million Years?"
     
    We learned that there are 3 ingredients for evolution: variation, selection, and time. Why is variation so important? Play Darwin's Survival Game to find out!
     
    If we really want to answer this question, we need to compare populations that have little or no genetic variation to populations that have lots of genetic variation. Here's what to do:
     
    Condition 1: NO variation
    • Your initial population should have NO genetic variation, so pick 3 of the exact same animal. (Read the hints on the screen to pick which traits you think will be best for your organism. Keep in mind the environment will change over the million years!)
    • Do not add any new traits by mutation during the game.
    Condition 2: LOTS of variation
    • Your initial population should have as much variation as possible. (some with stripes, some without, some fat, some thin, some with long legs some with short, etc.).
    • Add mutations as often as you can to help your species survive. (Unlike real life, you can pick which one you think will be best for the changing environment.)
    If you are working alone, you will need to do each condition at least 10 times to have decent data. In class, we will use the whole class's data to have enough trials. 
    In your notebook, make 2 columns, one for condition 1 (no variation) and the second for condition 2 (lots of variation). In each column, record the following data:
    • Number of surviving species
    • Fraction of species surviving
    • Percent of species surviving (show work)