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  • The Five Fingers of Evolution.

    五隻手指的進化

  • A thorough understanding of biology requires

    要透徹的了解生物學需要

  • a thorough understanding of the process of evolution.

    透徹地了解進化的過程

  • Most people are familiar with the process of natural selection.

    大多人對天擇的歷程並不陌生

  • However, this is just one of five processes that can result in evolution.

    然而,那只是能造就進化的五個歷程之一

  • Before we discuss all five of these processes,

    在我們探討這五個歷程之前,

  • we should define evolution.

    我們應該先定義進化

  • Evolution is simply change in the gene pool over time.

    進化就是指基因庫隨時間而改變

  • But what is a gene pool? And for that matter, what is a gene?

    但是何謂基因庫?更甚者,何謂基因?

  • Before spending any more time on genetics,

    在花更多時間在基因學上之前,

  • let us begin with a story.

    讓我們以一個故事作為開頭

  • Imagine that a boat capsizes, and 10 survivors swim to shore on a deserted island.

    想像一艘船翻覆了,十位生還者游上一座無人島的岸邊

  • They are never rescued, and they form a new population that exists for thousands of years.

    他們再也沒有被營救,並自成一個新的族群,生存了幾千年

  • Strangely enough, five of the survivors have red hair.

    說也奇怪,五位生還者有著紅頭髮

  • Red hair is created when a person inherits two copies of the red gene from their parents.

    紅色頭髮傳承自父母雙方的紅髮基因

  • If you only have one copy of the gene, you won't have red hair.

    如果你只得到一份這種基因,你不會有紅頭髮

  • To make this easier, we will assume

    為了讓事情簡單點,我們假設

  • that the five non-redheads are not carriers of the gene.

    五位非紅髮的人並沒有這種基因

  • The initial frequency of the red hair gene

    因此最初紅髮基因的機率

  • is therefore 50 percent, or 10 of 20 total genes.

    是 50%,或者說所有基因的二十分之十

  • These genes are the gene pool.

    這些基因即是基因庫

  • The 20 different genes are like cards in a deck

    這二十個不同的基因就像是一副牌

  • that keep getting reshuffled with each new generation.

    不斷在每個新的世代重新洗牌

  • Sex is simply a reshuffling of the genetic deck.

    性簡單來說就是基因重新洗牌的過程

  • The cards are reshuffled and passed to the next generation;

    卡片被重新洗牌並傳承至下一代;

  • the deck remains the same, 50 percent red.

    這副牌維持不變,一樣是 50%的紅色

  • The genes are reshuffled and passed to the next generation;

    基因被重新洗牌並傳承至下一代;

  • the gene pool remains the same, 50 percent red.

    基因庫維持不變,一樣是 50%的紅色

  • Even though the population may grow in size over time,

    即使人口數隨著時間逐漸成長,

  • the frequency should stay at about 50 percent.

    機率分佈應該要維持在 50%

  • If this frequency ever varies, then evolution has occurred.

    如果這個機率分佈有任何變動,表示有進化發生了

  • Evolution is simply change in the gene pool over time.

    進化就是指基因庫隨時間而改變

  • Think about it in terms of the cards.

    從卡牌的角度來思考看看

  • If the frequency of the cards in the deck ever changes,

    如果一副牌的機率分佈有任何改變,

  • evolution has occurred.

    進化已發生了

  • There are five processes that can cause the frequency to change.

    造成機率分佈改變的歷程有五種

  • To remember these processes, we will use the fingers on your hands,

    為了記住這些歷程,我們會用你的五隻手指作為代表,

  • starting from the little finger and moving to the thumb.

    從小指開始到拇指

  • The little finger should remind you that the population can shrink.

    小指告訴你人口可能會縮減

  • If the population shrinks, then chance can take over.

    如果人口縮減了,機率分佈便轉而接管

  • For example, if only four individuals survive an epidemic,

    例如,如果只有四個人從流行病中存活下來,

  • then their genes will represent the new gene pool.

    他們的基因就代表了新的基因庫

  • The next finger is the ring finger.

    下一隻手指是無名指

  • This finger should remind you of mating, because a ring represents a couple.

    這隻手指代表了擇偶,因為戒指代表著伴侶

  • If individuals choose a mate based on their appearance or location,

    如果一個人是基於對方的外表或地域來擇偶,

  • the frequency may change.

    機率分佈便可能會改變

  • If redheaded individuals only mate with redheaded individuals,

    如果紅髮的人只跟紅髮的人在一起,

  • they could eventually form a new population.

    他們最終會成為一個新的族群

  • If no one ever mates with redheaded individuals,

    如果沒有人要跟紅髮的人成為伴侶,

  • these genes could decrease.

    這些基因可能會消失

  • The next finger is the middle finger.

    下一隻手指是中指

  • The M in the middle finger should remind you of the M in the word "mutation."

    「中指」(middle finger) 裡的字母M可以讓你聯想到突變 (mutation) 中的字母M

  • If a new gene is added through mutation, it can affect the frequency.

    如果一個新的基因因突變而出現了,它會影響機率分佈

  • Imagine a gene mutation creates a new color of hair.

    設想一個突變的基因創造出新的髮色

  • This would obviously change the frequency in the gene pool.

    這理所當然地會影響基因庫中機率分佈

  • The pointer finger should remind you of movement.

    食指讓你聯想到行動

  • If new individuals flow into an area, or immigrate,

    如果新的一批人流進入一個區域,或者移民,

  • the frequency will change.

    機率分佈便會改變

  • If individuals flow out of an area, or emigrate,

    如果人流移出一個區域,或者遷徙,

  • then the frequency will change.

    機率分佈會隨之改變

  • In science, we refer to this movement as gene flow.

    在科學領域,我們稱這樣的改變為基因流動

  • All four of the processes represented by our fingers can cause evolution.

    我們四隻手指所代表的歷程皆會導致進化

  • Small population size, non-random mating,

    小型人口數、非隨機的擇偶、

  • mutations and gene flow.

    突變以及基因流動

  • However, none of them lead to adaptation.

    然而,這其中沒有任何一個能造就適應性

  • Natural selection is the only process

    天則是唯一

  • that creates organisms better adapted to their local environment.

    能讓生物體更加適應於其周遭環境的歷程

  • I use the thumb to remember this process.

    我用大拇指來記住這個歷程

  • Nature votes thumbs up for adaptations that will do well in their environment,

    大自然會對那些適宜環境的適應質表示讚許,

  • and thumbs down to adaptations that will do poorly.

    但對表現不佳的適應質表示否決

  • The genes for individuals that are not adapted for their environment

    在所屬環境適應不良的個體基因

  • will gradually be replaced by those that are better adapted.

    會逐漸被適應良好的取代

  • Red hair is an example of one of these adaptations.

    紅頭髮是適應質的其中一個例子

  • Red hair is an advantage in the northern climates,

    紅頭髮在北方的氣候中是一個優勢,

  • because the fair skin allowed ancestors to absorb more light

    因為白皙的皮膚使得祖先們可以吸收更多的光

  • and synthesize more vitamin D. Thumbs up!

    並形成更多維他命 D。給個讚!

  • However, this was a disadvantage in the more southern climates,

    然而,這在南方的氣候中卻形成一個劣勢,

  • where increased UV radiation led to cancer and decreased fertility.

    更多的紫外線輻射會導致癌症和生育率下降

  • Thumbs down!

    否決!

  • Even the thumb itself is an adaptation formed through the process of natural selection.

    即使是拇指本身,也是一個天擇後留下的適應質

  • The evolution that we have described is referred to as microevolution,

    我們所描述的進化只是所謂的微進化,

  • because it refers to a small change.

    因為它只涉及微小的改變

  • However, this form of evolution may

    然而,這樣的進化也可能

  • eventually lead to macroevolution, or speciation.

    逐漸演變成大進化,或新物種形成

  • Every organism on the planet shares ancestry with a single common ancestor.

    地球上每個生物體都與一個共同的祖先流著相同血液

  • All living organisms on the planet are connected back in time

    活在地球上的所有生物體在時間線上都是相連著的

  • through the process of evolution.

    透過進化的過程

  • Take a look at your own hand.

    看看你自己的手

  • It's an engineering masterpiece that was created by the five processes I just described,

    這是一項工程上的巨作,藉由我剛才介紹的五個歷程所創造出的,

  • over millions and millions of years.

    經過數以百萬年的時間

  • Can you recall the five main causes of evolution from memory?

    你可以回想出那五個造成進化的主要原因嗎?

  • If you can't, hit rewind and watch that part again.

    如果不行,按下倒轉然後重新看一次那一段

  • But if you can, give yourself or your neighbor a big five-fingered high five.

    但如果你做得到,跟你自己或是身旁的人大大地擊掌吧!

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B1 中級 中文 TED-Ed 進化 基因 歷程 機率 紅髮

【TED-Ed】五隻手指的進化 (TED : Five Fingers of Evolution - Paul Andersen)

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    Calvin Chen 發佈於 2012 年 12 月 17 日
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