Chapter 15 The Theory of Evolution

Section 15.1 Natural Selection and the Evidence for Evolution

Evolution What is evolution? A change in a population over time These changes is caused by many factors and are mapped out through fossils

Charles Darwin Darwin on HMS Beagle Ships naturalist

A Little Help Charles Lyell Thomas Malthus Increased food production leads to increased populations!! Geological changes on Earth take a long time and are always occurring!!

Darwin continues his studies Many species produce large numbers of offspring Individuals struggle to compete in changing environmental conditions Only some individuals survive the competition and produce offspring Charles Darwin ???

Darwin tests Heredity Artificial selection( 人工选择 ) : breeding organisms with specific traits in order to produce offspring with identical traits Controlled by humans; Can produce fast changes Pigeon Breeding

Natural Selection Organisms with favorable variations survive, reproduce, and pass their variations to the next generation. Traits are only favorable at that time and under specific conditions. No giant insects No giant lizards Humans do not have gills Controlled by nature Slow process

Structural adaptations arise over time Mimicry( 拟态 ):a structural adaptation that enables one species to resemble another species. Adaptations: Evidence for Evolution

–Camouflage( 伪装 ) ： an adaptation that enables species to blend with their surroundings Adaptations: Evidence for Evolution

Physiological adaptations( 生理性适应 ) can develop rapidly; “Micro-evolution” Adaptations: Evidence for Evolution

Fossils ： provide a record of early life and evolutionary history. Even with holes in the record, scientists can fill in the gaps Other Evidence for Evolution

Homologous structures( 同源器官 ): structural features with a common evolutionary origin Homologous structures can be similar in arrangement, in function, or in both. Anatomy

Analogous structures( 同功器官 ): the body parts of organisms that do not have a common evolutionary origin but are similar in function Anatomy

Vestigial structure ( 遗迹结构 ) ： a body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor Anatomy

Biochemistry Similar organisms have similar cellular organelles and/or enzymes Living things use DNA as a genetic blueprint Species in the 3 Domains use similar sized ribosomes

Section 15.2 Mechanisms of Evolution

Population: –Collection of members in a species –DNA explains the variation among individuals of a population Population genetics( 种群遗传学 ) –studies of the complex behavior of genes in populations of plants and animals Population Genetics and Evolution

Populations, not individuals, evolve Gene pool( 基因库 ) picture all of the alleles of the population’s genes as being together in a large pool Allelic frequency( 等位基因频率 ) the percentage of any specific allele in the gene pool Population Genetics and Evolution

Hardy-Weingberg Equation: p + q = 1 p = frequency of Dominate allele q = frequency of Recessive allele p 2 + 2pq + q 2 = 1 –75 (RR) = 75 x 2 = 150 R –15 (R’R’) = 15 x 2 = 30 R’ –10 (RR’) = 10 R and 10 R’ 160 R and 40 R’ –200 alleles total R alleles = 160/200 = 0.8 = p R’ alleles = 40/200 = 0.2 = q Calculating Allele Frequency AA= p 2 2Aa = 2pq aa= q 2 Aa AAAAa a aa 100 flowers; 75 are Red, 15 are White, and 10 are Pink. What are the frequencies for alleles R and R’? What are the genotype frequencies? RR= p 2 = = 0.64 R’R’= q 2 = = RR’= 2pq = 2(.8)(.2) = 0.32

Genetic equilibrium( 遗传平衡 ) The population is in genetic equilibrium when the frequency of its alleles for specific trait is the same in all its generations Population Genetics and Evolution

1) Mutation( 突变 ) 2) Gene flow( 基因漂流 ) The transport of genes by migrating individuals 3) Genetic drift( 遗传漂变 ) the alteration of allelic frequencies by chance events All three have can huge effects on small populations Changes in Genetic Equilibrium

Natural selection is usually the most significant factor that causes changes in established gene pools—small or large 3 Types of Natural Selection: 1) Stabilizing selection -favors the average 2) Directional selection -favors one extreme of a trait 3) Disruptive selection -favors both extremes of a trait Types of Natural Selection

Speciation( 物种形成 ) The evolution of new species Members of similar populations no longer interbreed to produce fertile offspring within their natural environment. The Evolution of Species

Polyploidy ( 多倍体 ) any individual or species with a multiple of the normal set of chromosomes Causes of Speciation

Reproductive Isolation: Species no longer can physically mate or offspring are sterile Behavioral Isolation: populations have different mating behaviors Causes of Speciation

Gradualism( 渐变论 ) species originate through a gradual change; small changes over a long time Punctuated equilibrium( 骤变论 ) speciation occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium Types of Evolution

Divergent evolution( 趋异进化 ) species that once were similar to an ancestral species diverge, or become increasingly distinct. Adaptive Radiation( 适应辐射 ) Ancestral species evolves into many species to fit a number of diverse habitats Convergent evolution( 趋同进化 ) distantly related organisms evolve similar traits Patterns of Evolution

That’s all !