1 00:00:00,000 --> 00:00:14,000 (Music) 2 00:00:14,000 --> 00:00:17,000 The Five Fingers of Evolution. 3 00:00:17,000 --> 00:00:20,000 A thorough understanding of biology requires 4 00:00:20,000 --> 00:00:22,000 a thorough understanding of the process of evolution. 5 00:00:22,000 --> 00:00:26,000 Most people are familiar with the process of natural selection. 6 00:00:26,000 --> 00:00:30,000 However, this is just one of five processes that can result in evolution. 7 00:00:30,000 --> 00:00:33,000 Before we discuss all five of these processes, 8 00:00:33,000 --> 00:00:35,000 we should define evolution. 9 00:00:35,000 --> 00:00:38,000 Evolution is simply change in the gene pool over time. 10 00:00:38,000 --> 00:00:42,000 But what is a gene pool? And for that matter, what is a gene? 11 00:00:42,000 --> 00:00:45,000 Before spending any more time on genetics, 12 00:00:45,000 --> 00:00:47,000 let us begin with a story. 13 00:00:47,000 --> 00:00:52,000 Imagine that a boat capsizes, and 10 survivors swim to shore on a deserted island. 14 00:00:52,000 --> 00:00:57,000 They are never rescued, and they form a new population that exists for thousands of years. 15 00:00:57,000 --> 00:01:00,000 Strangely enough, five of the survivors have red hair. 16 00:01:00,000 --> 00:01:05,000 Red hair is created when a person inherits two copies of the red gene from their parents. 17 00:01:05,000 --> 00:01:08,000 If you only have one copy of the gene, you won't have red hair. 18 00:01:08,000 --> 00:01:10,000 To make this easier, we will assume 19 00:01:10,000 --> 00:01:14,000 that the five non-redheads are not carriers of the gene. 20 00:01:14,000 --> 00:01:16,000 The initial frequency of the red hair gene 21 00:01:16,000 --> 00:01:20,000 is therefore 50 percent, or 10 of 20 total genes. 22 00:01:20,000 --> 00:01:22,000 These genes are the gene pool. 23 00:01:22,000 --> 00:01:25,000 The 20 different genes are like cards in a deck 24 00:01:25,000 --> 00:01:28,000 that keep getting reshuffled with each new generation. 25 00:01:28,000 --> 00:01:32,000 Sex is simply a reshuffling of the genetic deck. 26 00:01:32,000 --> 00:01:36,000 The cards are reshuffled and passed to the next generation; 27 00:01:36,000 --> 00:01:39,000 the deck remains the same, 50 percent red. 28 00:01:39,000 --> 00:01:43,000 The genes are reshuffled and passed to the next generation; 29 00:01:43,000 --> 00:01:47,000 the gene pool remains the same, 50 percent red. 30 00:01:47,000 --> 00:01:50,000 Even though the population may grow in size over time, 31 00:01:50,000 --> 00:01:53,000 the frequency should stay at about 50 percent. 32 00:01:53,000 --> 00:01:56,000 If this frequency ever varies, then evolution has occurred. 33 00:01:56,000 --> 00:02:00,000 Evolution is simply change in the gene pool over time. 34 00:02:00,000 --> 00:02:02,000 Think about it in terms of the cards. 35 00:02:02,000 --> 00:02:05,000 If the frequency of the cards in the deck ever changes, 36 00:02:05,000 --> 00:02:07,000 evolution has occurred. 37 00:02:07,000 --> 00:02:10,000 There are five processes that can cause the frequency to change. 38 00:02:10,000 --> 00:02:15,000 To remember these processes, we will use the fingers on your hands, 39 00:02:15,000 --> 00:02:17,000 starting from the little finger and moving to the thumb. 40 00:02:17,000 --> 00:02:21,000 The little finger should remind you that the population can shrink. 41 00:02:21,000 --> 00:02:24,000 If the population shrinks, then chance can take over. 42 00:02:24,000 --> 00:02:28,000 For example, if only four individuals survive an epidemic, 43 00:02:28,000 --> 00:02:31,000 then their genes will represent the new gene pool. 44 00:02:31,000 --> 00:02:33,000 The next finger is the ring finger. 45 00:02:33,000 --> 00:02:38,000 This finger should remind you of mating, because a ring represents a couple. 46 00:02:38,000 --> 00:02:41,000 If individuals choose a mate based on their appearance or location, 47 00:02:41,000 --> 00:02:43,000 the frequency may change. 48 00:02:43,000 --> 00:02:47,000 If redheaded individuals only mate with redheaded individuals, 49 00:02:47,000 --> 00:02:49,000 they could eventually form a new population. 50 00:02:49,000 --> 00:02:52,000 If no one ever mates with redheaded individuals, 51 00:02:52,000 --> 00:02:54,000 these genes could decrease. 52 00:02:54,000 --> 00:02:55,000 The next finger is the middle finger. 53 00:02:55,000 --> 00:02:59,000 The M in the middle finger should remind you of the M in the word "mutation." 54 00:02:59,000 --> 00:03:03,000 If a new gene is added through mutation, it can affect the frequency. 55 00:03:03,000 --> 00:03:07,000 Imagine a gene mutation creates a new color of hair. 56 00:03:07,000 --> 00:03:10,000 This would obviously change the frequency in the gene pool. 57 00:03:10,000 --> 00:03:12,000 The pointer finger should remind you of movement. 58 00:03:12,000 --> 00:03:16,000 If new individuals flow into an area, or immigrate, 59 00:03:16,000 --> 00:03:17,000 the frequency will change. 60 00:03:17,000 --> 00:03:20,000 If individuals flow out of an area, or emigrate, 61 00:03:20,000 --> 00:03:22,000 then the frequency will change. 62 00:03:22,000 --> 00:03:25,000 In science, we refer to this movement as gene flow. 63 00:03:25,000 --> 00:03:30,000 All four of the processes represented by our fingers can cause evolution. 64 00:03:30,000 --> 00:03:34,000 Small population size, non-random mating, 65 00:03:34,000 --> 00:03:37,000 mutations and gene flow. 66 00:03:37,000 --> 00:03:39,000 However, none of them lead to adaptation. 67 00:03:39,000 --> 00:03:41,000 Natural selection is the only process 68 00:03:41,000 --> 00:03:45,000 that creates organisms better adapted to their local environment. 69 00:03:45,000 --> 00:03:48,000 I use the thumb to remember this process. 70 00:03:48,000 --> 00:03:52,000 Nature votes thumbs up for adaptations that will do well in their environment, 71 00:03:52,000 --> 00:03:55,000 and thumbs down to adaptations that will do poorly. 72 00:03:55,000 --> 00:03:59,000 The genes for individuals that are not adapted for their environment 73 00:03:59,000 --> 00:04:02,000 will gradually be replaced by those that are better adapted. 74 00:04:02,000 --> 00:04:05,000 Red hair is an example of one of these adaptations. 75 00:04:05,000 --> 00:04:08,000 Red hair is an advantage in the northern climates, 76 00:04:08,000 --> 00:04:12,000 because the fair skin allowed ancestors to absorb more light 77 00:04:12,000 --> 00:04:15,000 and synthesize more vitamin D. Thumbs up! 78 00:04:15,000 --> 00:04:19,000 However, this was a disadvantage in the more southern climates, 79 00:04:19,000 --> 00:04:23,000 where increased UV radiation led to cancer and decreased fertility. 80 00:04:23,000 --> 00:04:25,000 Thumbs down! 81 00:04:25,000 --> 00:04:29,000 Even the thumb itself is an adaptation formed through the process of natural selection. 82 00:04:29,000 --> 00:04:34,000 The evolution that we have described is referred to as microevolution, 83 00:04:34,000 --> 00:04:36,000 because it refers to a small change. 84 00:04:36,000 --> 00:04:38,000 However, this form of evolution may 85 00:04:38,000 --> 00:04:41,000 eventually lead to macroevolution, or speciation. 86 00:04:41,000 --> 00:04:46,000 Every organism on the planet shares ancestry with a single common ancestor. 87 00:04:46,000 --> 00:04:49,000 All living organisms on the planet are connected back in time 88 00:04:49,000 --> 00:04:52,000 through the process of evolution. 89 00:04:52,000 --> 00:04:53,000 Take a look at your own hand. 90 00:04:53,000 --> 00:04:58,000 It's an engineering masterpiece that was created by the five processes I just described, 91 00:04:58,000 --> 00:05:00,000 over millions and millions of years. 92 00:05:00,000 --> 00:05:04,000 Can you recall the five main causes of evolution from memory? 93 00:05:04,000 --> 00:05:07,000 If you can't, hit rewind and watch that part again. 94 00:05:07,000 --> 00:05:18,138 But if you can, give yourself or your neighbor a big five-fingered high five.