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Natural Selection Scenarios Bell Ringer • Write your learning targets at the top of your notebook page • Silently complete the exit quiz from last class Agenda • • • • • • Bell Ringer (10 minutes) Review (10 minutes) Scenario Practice (10 minutes) Group Activity (40 minutes) Independent Practice (10 minutes) Exit Quiz (10 minutes) Essential Question • How does overproduction, inherited variation and the struggle to survive allow for natural selection? “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” Charles Darwin Natural Selection • Natural Selection: the process in nature where the most fit organisms survives to reproduce and pass on traits to offspring • Natural selection leads to evolution • There are three requirements for natural selection to occur 1. Overproduction=organisms produce more offspring than needed and not all offspring will survive – Offspring will compete for resources 2. Inherited Variation=there are differences among the organisms in a population caused by genetic mutations and recombination – Some variations will be better for survival than others 3. Struggle to survive= organisms must compete for resources and fight to stay alive • Overproduction + inherited variation + struggle to survive = differential reproductive success • Differential reproductive success=individuals with certain traits are more likely to survive and reproduce; those traits will be more frequent in the population You should be: Natural Selection Example • Which rabbit has a better chance of surviving in the North Pole? Why? You should be: Natural Selection Example Oh, snap, I just found dinner. Gosh darn it, no rabbits here. All the brown rabbits die Only one white rabbit dies White rabbits have babies Now we have ALL white rabbits! Now assume only fat rabbits can survive the cold Now we have all fat white rabbits - We can say that the rabbits evolved into fat white rabbits. - The process is called evolution. Moth Scenario In England, a species of moth called the peppered moth lives on trees. Peppered moths can either look light with gray spots or can look dark. During the 1800s, the Industrial Revolution changed the landscape of England. New coal-powered factories spewed tons of dirty smoke into the air, blanketing the forests with soot. The tree trunks were darkened by the pollution. When this happened, the light colored moth form was easier to spot than the dark form, and as a result more were eaten. By 1895, dark moths accounted for nearly 100% of the total population in some forests. How is this natural selection? Group Activity • We will simulate natural selection of finches on the Galapagos islands • It is crucial that you follow ALL INSTRUCTIONS and LISTEN CAREFULLY • If you are not following instructions, you will not participate Sexual Selection Scenario • Felix always felt a little awkward with his extra-long trunk. When he reached adulthood, he found out that ALL the female elephants found this once strange trait, VERY attractive. • Predict how this trait may become very common in the elephant population over several generations. Behavioral Selection • Lemmings are small rodents who reach sexual maturity a month after birth and have large litters. Periodically, when their populations exceed their resources (carrying capacity), groups of lemmings will jump into water. This was historically thought of as a mass suicide. • Clearly, suicide is NOT FAVORABLE TO THE INDIVIDUAL. How can you explain this behavior as being advantageous to the ENTIRE lemming population? Background • You and your classmates will simulate the survival of birds called medium ground finches on Daphne Major, one of the Galápagos Islands. This bird species has three possible variations in beak shape: deep, cutting, and pointy. Each “bird’s” ability to acquire food will determine whether it dies, or whether it survives. • Medium ground finches typically feed on small, soft fruit and seeds. The birds prefer soft seeds because they are easier to crack. However, during periods of drought, food becomes scarce. The birds are forced to eat more hard seeds that are difficult to break open. Birds with deeper beaks are better able to crack open hard seeds than birds with shallower beaks. These variations in beak depth made it possible for some of the medium ground finches to get enough food to survive and reproduce during long droughts. • After simulating changes in the bird population for six generations, you will analyze data to discover how the frequency of each beak phenotype in the population changed over the generations Variables • Independent Variable: what are we purposefully manipulating in the activity? • Dependent Variable: what are we going to measure in the activity? • Constants: what will be kept the same? Hypothesis • As a group, form an “If…then…because…” hypothesis about what will happen in the activity. • For example: “If we test (independent variable) then we will see (dependent variable) because…” Procedures • For each round, use your beak and to pick up as much food as you can and put it your “nest” (plastic bag) • You need to collect 10 pieces of food by the time the timer runs out to stay alive. • You may only pick up ONE piece at a time. • If you collect 15 or more, you “reproduce” (get another of your beak type from Mrs. Franklin). Practice Round • Practice gathering “seeds” for one minute Data Table Independent Practice Big Idea: Bacterial Resistance Exit Quiz Homework • Finish the group activity worksheet!