Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
一、參選類別(請勾選): ■「學士班必修課程與全校性共同課程」候選人 □「其他(學士班選修及研究所) 課程」候選人 四、近二年任教之學士班必修課程與全校性共同課程 學年度 學期 當學期 課號 課程名稱 開課單位 開課對象 修課 (系級班別) 人數 97 1 1495 普通生物學(一) 生科系 生科系大一 59 98 1 1557 普通生物學(一) 生科系 生科系大一 63 國立交通大學生物科技學院 助理教授 林勇欣 The “mystery of mysteries” that captivated Darwin is speciation, the process by which one species splits into two or more species Speciation fascinated Darwin (and many biologists since) because it is responsible for the tremendous diversity of life, repeatedly yielding new species that differ from existing ones Speciation explains not only differences between species, but also similarities between them (the unity of life) Speciation also forms a conceptual bridge between microevolution, changes over time in allele frequencies in a population, and macroevolution, the broad pattern of evolution over long time spans Chapter 23 – microevolution Chapter 25 – macroevolution In this chapter, we will explore the “bridge” – the mechanisms by which new species originate from existing ones First, we need to establish what we actually mean when we talk about “species” The tephritid fly has distinctive dark bands on its wings. When disturbed, the fly holds its wings perpendicular to its body and waves them up and down. Entomologists had noticed that this display seems to mimic the leg-waving, territorial threat display of jumping spiders. • The first step in any evolutionary analysis is to phrase the question as precisely as possible • In this case: Do the wing markings and the wing waving of the fly mimic the threat displays that jumping spiders use on each other, and thereby allow the flies to escape predation? • • When the researchers tested treatments A, C, and E against other predators, all of the test flies were captured and eaten There was not even an appreciable difference in time-tocapture among the three treatment groups The initial allele frequencies are 0.01 for B1 and 0.99 for B2 A general treatment of selection If there are two alleles, B1 and B2, with frequencies p and q We incorporate selection by imagining that B1B1 zygotes survive to adulthood at rate w11; B1B2 zygotes survive at rate w12; and B2B2 zygotes survive at rate w22 All individuals that survive produce the same number of offspring We can therefore refer to the survival rates as fitnesses The average fitness for the whole population, w, is given by the expression: w = p2w11 + 2pqw12 + q2w22 ≦ 1 A general treatment of selection The average fitness for the whole population, w, is given by the expression: w = p2w11 + 2pqw12 + q2w22 ≦ 1 The new frequencies of the genotypes are: B1B1 B1B2 B2B2 p2w11 2pqw12 q2w22 w w w The new frequency of B1 is p 2 w11 pqw12 p' w The new frequency of B2 is pqw12 q 2 w22 q' w A general treatment of selection It is instructive to calculate the change in the frequency of allele B1 from one generation to the next This value, ∆p, is the new frequency of allele B1 minus the old frequency of B1: p 2 w11 pqw12 p p' p p w p 2 w11 pqw12 p w w p pw11 qw12 w w The change in the frequency of allele B2 from one generation to the next is q q pw12 qw22 w w An algebraic treatment of selection on recessive and dominant alleles frequencies fitness AA p2 wAA = 1 Aa 2pq wAa = 1 aa q2 waa = 1 + s Where s called selection coefficient pqwAa q 2 waa pqwAa q 2 waa q1 sq q' 2 2 p wAA 2 pqwAa q waa 1 sq 2 w If a is a lethal recessive, then s is equal to -1 q1 q q1 q q q' 2 1 q 1 q 1 q 1 q An algebraic treatment of selection on recessive and dominant alleles frequencies fitness AA p2 wAA = 1 + s Aa 2pq wAa = 1 + s aa q2 waa = 1 p 2 wAA pqwAa p 2 wAA pqwAa p1 s p' 2 2 p wAA 2 pqwAa q waa 1 2sp sp 2 w If A is a lethal dominant, then s is equal to -1 A lethal dominant is eliminated from a population in a single generation p1 1 p' 0 2 1 2 p p An algebraic treatment of selection on recessive and dominant alleles