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• ATB: OPEN LOGBOOK TO DOTS ACTIVITY • DO THE 8 QUESTIONS YOU ATTACHED AT THE END OF THE PERIOD YESTERDAY • PLANNER: HW-CHECKUP PRACTICE DUE FRIDAY • LOGBOOK CHECK AND CHECKUP ON FRIDAY • LEAVE THE BACK TWO (SMALL) TABLES EMPTY, PLEASE Questions to answer in your lab book 1. Which, if any, shades of paper squares survived better than others in the second, third, and fourth generation starting populations of paper squares? 0% color survived the best. 2. What might be the reason that predators did not select these shades as much as they did other shades? They blended into the environment and were more difficult to find. 3. What effect did capturing a particular shade square have on the numbers of that shade in the following generations? The shaded squares that were captured were decreased in number in the next generation. 4. What is the average color in generation 1? What is the average color in generation 5? Generation 1 = 50% shade Generation 5 = 13 % shade 5. Did any 50% shade squares turn into 0% squares? Any 100% squares turn No into 50%? 6. If none of the squares changed into other squares, then why is the average member of the dot/square population different after 5 generations? The 100% shaded squares were “eaten” and could not pass on traits to the next generation. 0% squares continued to survive and pass on traits to next generation. 7. How has the amount of variation in the population changed over time? The amount of variation has decreased in the population over time. Most of the population has 0% shade. 8.What affect do you think the environment (habitat and predator) has on the average characteristic and the variation of a population? The environment determines which characteristics are favorable. • MAKE A NEW ENTRY TITLED “EVOLUTION AND NATURAL SELECTION” • GET A NOTES SHEET FROM THE FRONT COUNTER THE HORSE ON THE LEFT IS AN ANCESTOR OF THE HORSE ON THE RIGHT. BASED ON WHAT WE’VE LEARNED IN THIS UNIT ABOUT VARIATION AND CHANGES DUE TO THE ENVIRONMENT—HOW COULD THE AVERAGE HORSE WIND UP LOOKING LIKE THE ONE ON THE RIGHT (AFTER A LOOOOONG TIME). USE LEG LENGTH AS YOUR EXAMPLE • DOTS-- GENETIC OR GET USED TO THE WHITE BOARD? • ANTIBIOTIC RESISTANCE—GENETIC OR “GET USED TO”? • LACTOSE INTOLERANCE– GENETIC OR “GET USED TO” MILK • IF AN ORGANISM DOESN’T HAVE THE TRAIT—CAN THEY DEVELOP IT? EVOLUTION YOUR OWN DEFINITION AND AN EXAMPLE Evolution: Change in the heritable (genetic) traits of a population over time Note: when we discuss evolution, we are talking about populations changing, not individuals Natural selection: The main mechanism by which evolution occurs 4 Conditions for Natural Selection: 1. Variation: Individuals in a population are not identical to each other. 2. Inheritance: Traits are passed to offspring; traits have a genetic basis 3. Environmental population limits: Environmental limiting factors prevent all individuals from surviving to reproduce; some die young. 4. Environmental selection: • Individuals in the population with more favorable (advantageous) traits are the ones that survive to reproduce. • Individuals without advantageous traits die before reproducing. These factors result in a change in the average trait of the population… Biologists call this EVOLUTION! 1. VARIATION Members of a population have traits similar to the average trait of the entire population, but they are not identical. YOUR TURN: Using height as an example, sketch a graph to represent the statement above. Mean (average) height Frequency • Height (cm) 2. INHERITANCE • DNA determines the traits of individuals DNA mRNA protein trait • Individuals inherit DNA from their parents • This causes the traits of the offspring to resemble the traits of the parents 3. ENVIRONMENTAL POPULATION LIMITS Population A. For all species, if every individual born into a population were to reproduce, the population would grow exponentially Time 3. ENVIRONMENTAL POPULATION LIMITS Population B. Environmental factors (limiting factors) prevent the majority of individuals from surviving to reproduce Time 4. SELECTION • Individuals without advantageous traits die before reproducing. Individuals with advantageous traits survive to reproduce. Frequency • These individuals survive to reproduce Characteristic Populations change, not individuals Frequency • The “average” characteristic or other measure of the population changes over generations These individuals survive to reproduce Characteristic The environment is the selective force behind evolution • The environment determines what characteristics are “favorable” • Because the environment changes over time, the characteristic that is more favorable for a population changes • Therefore, characteristics of the population change, or evolution occurs Questions for discussion •Describe how variation existed in the PAPER SQUARES . •Describe how inheritance existed in the PAPER SQUARES. •Describe how population limits existed in the PAPER SQUARES. •Describe how environmental selection affected the PAPER SQUARES. •PEPPERED MOTHS Evolution of Peppered Moths Dark form Peppered form Explain the evolution of color in the peppered moth population. 1. Describe what trait evolved. 2.Describe how each of the 4 conditions for natural selection exists in the moth example: a) Variation b) Inheritance c) Population limits d) Selection (Environmental Selection) Make a graph that shows how the average color changed over several generations • The population of peppered moths became darker in color near industrial areas. • Originally, some moths were dark, some moths were peppered (light). • Color is determined by genes inherited from parents. • Not all moths survive to reproduce- some are eaten by birds. • Pollution killed lichen and made the environment darker, so darker moths were better camouflaged and not eaten as much as peppered (light) moths. • This caused the average color of the moth population to become darker • Apply the 4 factors of Natural Selection to the Giraffe Population • Variation • Inheritance • Population Limits • Environmental Selection • Make a graph that shows there is a variety of neck lengths, but most are like the average • Make a graph that would show how the average neck length has changed over time (to be longer) •Checkup practice • A POPULATION OF BIRDS HAD BEAKS WITH LENGTHS RANGING FROM 5CM TO 15CM. THESE BIRDS ATE MOSTLY FRUIT AND A FEW SEEDS— ONLY LONG-BEAKED BIRDS CAN EAT SEEDS. AFTER 3 YEARS OF DROUGHT, THE AVERAGE LENGTH OF BEAK INCREASED. • APPLY THE 4 FACTORS OF NATURAL SELECTION TO THE BIRDS • A GRAPH THAT SHOWS THE BIRDS’ BEAKS ARE SIMILAR BUT NOT IDENTICAL TO ONE ANOTHER • A GRAPH THAT SHOWS HOW THE AVERAGE BEAK LENGTH INCREASED OVER A FEW YEARS Starting Population Generation number 1 Surviving Population 15cm 10cm 5cm 15cm 5cm 10cm 6 8 7 3 6 7 2 6 12 14 4 9 13 3 8 18 26 4 15 24 4 8 30 48 • APPLY THE 4 FACTORS OF NATURAL SELECTION • GRAPH THAT SHOWS HOW THE AVERAGE COULD CHANGE OVER TIME • CALCULATE THE AVERAGE TRAIT OVER GENERATIONS (DATA TABLE WILL BE PROVIDED—BRING YOUR OWN CALCULATOR) • EXPLAIN WHAT WOULD HAPPEN IF ONE OF THE 4 FACTORS WERE NOT PRESENT