Assignment Content Background: Evolution is the change in gene frequency between generations. Natural selection is one of the mechanisms by which this change occurs. This idea was first formulated by Charles Darwin in his work On the Origin of Species, which was first published in 1859. Darwin's studies of animals, both living and extinct, allowed him to see much of the variation within populations. He reasoned that the variations in traits might affect the ability of an individual to secure resources, to survive, and to reproduce. He noted that on the Galapagos Islands, near Ecuador, the finches varied slightly from each other, but resembled the mainland finches to some extent. He reasoned that those animals now present could have descended from those living in the past, but with changes. Darwin gradually developed a theory of natural selection to explain how such changes could come about. Here are the basic components of the idea: 1) All populations vary naturally. 2) All populations produce more offspring than can survive. 3) Resources are limited so that there is competition within species. 4) Variations allow some organisms within a species to survive and reproduce better than others. 5) These favorable traits are passed down from generation to generation--they are heritable. A population exhibits immense variation in its individual members, all of which are of the same species, but vary in the details of their shared characteristics. All of the genes in the entire population make up the gene pool. Remember that each kind of gene may exist in two or more slightly different forms called alleles. Individuals inherit different combinations of alleles, which leads to variations in phenotype. Alleles that promote survival or reproduction increase in frequency over generations, resulting in individuals that differ in one or more heritable traits-evolution. There are several sources of variation within populations. Gene mutations create new alleles. Crossing over during meiosis I leads to new combinations of alleles. Independent assortment in meiosis I mixes paternal and maternal chromosomes in the gametes. Fertilization mixes alleles from two parents. Changes in chromosome structure or number can lead to the loss, duplication, or alteration of alleles. Only mutation creates new gene forms; all the other sources of variation shuffle existing genes. Selection may be defined as any non-random force that causes differential reproductive success. There are different types of selection, based on the effects that the selection has on the population. One of these is directional selection. Directional selection shifts allele frequencies in a consistent direction in response to environmental pressures. Forms of traits at one end of the range of variation become more common than midrange forms. A giraffe's long neck is a good example of directional selection. An extreme characteristic (i.e. giraffe's long neck) is selected for by the environment. Another type of selection is stabilizing selection. Stabilizing selection favors the most common forms of a trait in a population. It counters the effects of mutation, genetic drift, and gene flow. In other words, this type of selection favors individuals who are closest to the average trait. An example of this involves human babies. Babies that weigh about seven pounds at birth have better survival chances than those that are larger, or smaller. There are many other examples of stabilizing selection. These may include body size in many animals, clutch size in birds, and patterns and colors of various animals. A third way that selection can affect populations is disruptive selection. In this type of selection, two or more phenotypes are maintained permanently in the population. Intermediate forms are selected against. Bill size in some birds may be an example of this. Each of these types of selection can be seen below: Directional Selection Selection against one extreme HOW does the trait change? Stabilizing Selection Selection against both extremes Population after selection Original population LONG Population after selection Original population LONG SHORT SHORT MEDIUM FOR: one extreme trait AGAINST: the other extreme SHORT MEDIUM FOR: moderate traits AGAINST: both extremes Disruptive Selection Selection against the mean MEDIUM -Population after selection Original population LONG FOR: both extremes AGAINST: moderate traits + EX. Long wiggly tails look like a snake and scare predators. The longer the tail, the more it looks like a snake. EX. Short tails mess up the cat's balance. Long tails drag on the ground. Medium tails are best. EX. Short tails help keep predators from catching you on the ground. Long tails are good for balance in the trees. Medium tails don't help. In this lab, we will be playing card games to investigate the 3 types of selection (directional, stabilizing, disruptive). You will need a partner to play some common card games. Focus on the results, and how it applies to natural selection In these experiments we will use familiar card games to simulate natural selection. The cards represent proportions of the population and not actual numbers. For example in a normal deck of cards Kings represent 1/13th of the total population. (4 kings out of 52 cards). So in these experiments, as the deck of cards gets smaller, do not infer the population of organisms is also shrinking. Assume that the number of organisms is stable, (at perhaps 1,000,000, and the only thing that is changing is the proportion of different organisms. For example, if in the final deck of cards, there are only 10 cards, and 1 of those is a Jack, then Jacks make up 10% of the total population. Question 1 Which of the following are components of natural selection (select all that apply)? A) Inheritance B Variation C) Selection D) Adaptation E Time 0.5 Points Experiment 1: Materials needed: 2 decks of cards (you will have one deck and your partner will use the other deck......you will not exchange any cards so it may help to use different styles of cards....for instance a blue deck of cards and a red deck of cards) We will play a modified version of the children's card game war. 1. Each player needs to shuffle his/her deck of cards. 2. Place the cards face down in front of you, and your partner should do the same. 3. Each player flips over the top card of his/her deck. 4. The player with the higher card, wins the match. Each player will create two piles of cards (one will be the "living" pile and the other will be the "dead" pile). Put the winning card in the "live" pile. 5. The player who lost the battle will put his card in the "Dead" pile. This card failed to compete and therefore died out. 6. In case of a tie, both of the players put their cards in their "living" pile. 7. The person who finished the deck first, ends the round. After this occurs a. Put the cards from the "living" pile in order from 2-A b. Count the total number of "living" cards (KEEP THE LIVING CARDS SEPARATE FROM THE DEAD CARDS.....YOU WILL USE THEM AS THE ROUNDS PROCEED) c. Count the number of each type of card. Fill in the table below (specifically the R1- # column). d. Once you have listed the number of each card still in the living pile, calculate the percentage of each card left in the pile. For example, if you had 1 ace left out of 26 living cards, you would have 3.8% aces (1/26 -0.038). e. Then calculate the total population number by multiplying your answer to the % by 1 million (0.038 * 1,000,000). 8. You will play 3 more rounds..........pay attention to how the living pile changes as the game proceeds (what cards are present in the first round vs the final round). To do this: a. KEEP ONLY LIVING CARDS. Reshuffle the living deck, and play again, ONLY using the cards from the living pile. DO NOT add cards back in from the "dead" pile. This means each round, you will be playing with less and less cards. 9. Repeat this procedure 3 more times. 10. The cards in the final "live" pile are the organisms most fit for their environment (at the end of round 4). Question 2 Fill in the following table. Note: "R" indicates the round. For each round, calculate: # Number of each card of that value remaining in the deck (these are the "living" cards after each round). % Number of each card / total number of cards. Example 1/10 = 10% Pop= Percentage times 1,000,000 (in this class we will assume a fixed population) R3 33 R4 14 1.5 Points 24 R4 R4 % Pop # % Pop R1 R1 R1 R2 R2 R2 R3 123 R3 Card # % Pop. # % Pop 2 3 4 5 6 7 8 6 10 10 J Q K A Total #/n Experiment 2: Materials needed: 2 decks of cards. We will demonstrate natural selection by playing a modified version of blackjack (21) against your lab partner. In this version of blackjack you already have two cards played worth 12 points [So each time you flip a card you are starting with a 12.....so if you flip a 6 and your partner flips a 7 then you are sitting with 18 (12+6=18) and they are sitting with a 19]. You and your partner will play one card in his/her deck. The person who finished closest to 21 without going over wins. Put the winning card in the living pile. Play through the entire deck (you and your partner will have a live pile and a dead pile). Remember the point values for face cards are 10, the ace is worth 1 or 11, and the number cards are worth their total. For example a 6 is worth six points. Play through the decks 3 times, using only the living decks in round 2 and 3. DO NOT put the "dead" cards back in the deck at any point. After the 3rd round answer the following questions. Experiment 2 tutorial CC Powered by Panopto Question 7 1.5 Points Complete the table using the deck of cards following your third round of Blackjack. Remember, the directions stated "Play through the decks 3 times, using only the living decks in round 2 and 3." This means you should have continued playing with decreased deck sizes in each round, without returning the "dead" cards to the deck at any point. 2 3 4 5 6 7 80 9 10 10 J Q K A totals # % Pop. Question 8 Which card dominates the winning deck? A Ace, as they are the high card B 9, as they cannot be beat C 2, as they are the low card D) None of the above Question 9 Is this different from the final deck found from playing war. A Yes - there are less low cards in the pile as they areallkilled off in this experiment B Yes - there are less high cards in the pile as they areallkilled off in this experiment CNo- the compositions are very similar 0.5 Points 0.5 Points/n Experiment 3: You only need one deck of cards for this experiment, and do not need a partner. You can complete this portion on your own. In this experiment the deck of cards represents a school of fish. The number on the cards indicates the weight of each fish. These fish live happily together until a new predator (the teacher) is introduced to their school. This particular predator weighs 20 pounds. As most predators are, this fish is fairly cautious and will not eat any fish greater than or equal to its body weight. Also any of the small fish in the school (defined as being less than 1/4 the weights of the predator) are able to hide from the predatory fish. Using this information, go through your school of fish (deck of cards) and remove all of the fish eaten by the predator. Hint: Think about it this way..... Your fish weighs 20 pounds and won't eat anything equal to or more than half of its weight, which means it will eat anything less than pounds, and anything larger than that will not be eaten, and will live (will remain in the pile). Anything less than 1/4 of its size, or less than pounds, can hide from it and will survive as well (will remain in the pile). Therefore, anything between and pounds will be eaten, and will therefore die off (be removed from the pile). Experiment 3 tutorial Powered by Panopto > CC Question 10 Complete the following table: 2 3 4 5 6 7 00 8 6 10 10 J - 0 K A % Pop. Use the editor to format your answer 1.5 Points Question 11 0.5 Points Describe the expected composition of the final deck (which cards are, and are not present). There may be more than one correct answer. The survivors include... A... individuals less than 5 pounds B... individuals more than 9 pounds ... individuals between 5 and 9 pounds D ... individuals between 5 and 10 pounds E some individuals more than 5 pounds Analysis Summary Question 12 Match the type of natural selection observed to the experiment. Prompts Experiment 1 Answers Select match 2 Experiment 2 Select match 3 Experiment 3 Select match Additional content Drag and drop files here or click to add text. 1.5 Points