1.族群(population)的定義：A localized group of individuals that belong to the same species.
2.基因庫(gene pool)的定義：All of the genes in a population
3.基因頻率的概念：allele frequency and genotype frequency
4.microevolution：evolution within species
changes of frequency
發生的原因有兩點：第一個是mutation(新的變異產生)，第二個是evolutionary mechanisms(改變基因的頻率)
A. evolutionary mechanisms:
(1) natural selection :
a. directional selection：at one extreme of phenotype
b. stabilizing selection : favors individual with intermediate phenotypes
c. disruptive selection : favors the survival of two or more different genotypes
d. balancing selection : maintain genetic diversity
two mechanisms : balanced polymorphism : heterozygotes advantage
negative frequency-dependent selection : rare individuals have higher fitness
(2) random genetic drift：發生在樣本少的population，可能有兩種現象的發生
a. bottleneck：
b. founder effect：
(3) migration：gene flow between populations
(4) nonrandom mating : 基因的配對不是隨機的
Assortative：similar phenotypes -----homozygotes increase
Disassortative： dissimilar phenotype --- heterozygote increase
Inbreeding ：近親，增加同型合子的機率
(5) neutral theory of evolution：non-Darwinian evolution
neutral variation ：沒有表型的變化，故無天擇的影響，完全是靠genetic drift 的影響
(6) sexual selection：性擇
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