Chapter 16 Darwin’s Theory of 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!!

Lamarck’s Malarkey (nonsense) Jean-Baptiste Lamarck: Acquired characteristics  living things can change to be the best to survive Acquired traits  parents can pass down these traits to their children A giraffe stretches every day to reach higher and higher branches; so his neck gets longer He eats better, survives, and passes his long neck onto his children Animals change themselves to fit their environments!!

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: 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  a structural adaptation that enables one species to resemble another species. Adaptations: Evidence for Evolution

Camouflage  an adaptation that enables species to blend with their surroundings Adaptations: Evidence for Evolution

Physiological adaptations 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: structural features with a common evolutionary origin Homologous structures can be similar in arrangement, in function, or in both. Anatomy

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

Vestigial structure : 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

Ch. 17 Evolution of Populations

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 picture all of the alleles of the population’s genes as being together in a large pool Allelic frequency 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 The population is in genetic equilibrium when the frequency of its alleles for specific trait is the same in all its generations 5 Conditions of the Hardy-Weinberg Principle 1)Random mating  must be no selection of who mates with who (sexual selection) 2)Infinitely Large Population  small populations are effected by change more 3)No Genetic Drift  gene pool must stay the same 4)No Mutations  gene pool must stay the same 5)No Natural Selection  all gene combinations have an equal chance to survive If all are met, the population will not change Population Genetics and Evolution

1) Mutation 2) Gene flow The transport of genes by migrating individuals 3) Genetic drift 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 The evolution of new species Members of similar populations no longer interbreed to produce fertile offspring within their natural environment 4 Isolating Mechanisms: 1)Geographical Isolation: Physical separation of two groups; often have different environmental factors The Evolution of Species

Polyploidy any individual or species with a multiple of the normal set of chromosomes Causes of Speciation

2) Reproductive Isolation: Species no longer can physically mate or offspring are sterile 3)Behavioral Isolation: populations have different mating behaviors 4) Temporal Isolation: Two groups reproduce at different times Causes of Speciation

Molecular Clock: All organism have DNA and all DNA mutates at a certain rates –Bacteria mutations per genome per generation –Humans 1.0 x mutations per site per generation Neutral mutation rates can show how long ago two species might have split Molecular Evolution

That’s all !