Module 1: Evolution MonthDayTopic Sept8Mechanisms of evolution I 11Mechanisms of evolution II 13Speciation 15Macroevolution 18Biodiversity 20The history of plants 22Molecular evolution Exam review First mid-term exam

Outline What is it that evolves? Mechanisms of microevolution

Evolution:

Descent with modification

Evolution: Descent with modification Natural selection:

Evolution: Descent with modification Natural selection: Differential reproductive success

What is it that actually evolves?

Populations are the essential units that evolve

Population: A group of individuals of the same species living in the same area at the same time

Darwin’s theory Charles Darwin ( s): –Fact #1: Overproduction and struggle for existence (Malthus) –Fact #2: Heritable individual variation within populations (Mendel) –The inescapable conclusion: Differential or unequal reproductive success yields evolution.

Ever since Darwin... Mendel develops theory of heredity (1860s)

Ever since Darwin... Mendel develops theory of heredity (1860s) –Parents pass onto their offspring discrete, heritable factors that are responsible for inherited traits.

Ever since Darwin... Mendel develops theory of heredity (1860s) –Parents pass onto their offspring discrete, heritable factors that are responsible for inherited traits. –Discrete, heritable factors = genes –Genes act in predictable ways

Genotype: genetic constitution of an individual Phenotype: interaction between genotype and environment Remember: offspring inherit genes, not phenotypes

Survival of the fittest...

Genes are the raw materials of evolution Populations are the essential units that evolve

Microevolution Change in the frequencies of genotypes in a population

Genetics Gene: unit of heredity, basis of phenotype Alleles: alternate forms of a gene Haploid: 1 set of chromosomes, 1 copy of an allele Diploid: 2 sets of chromosomes, 2 copies of an allele

Genetics Dominant allele: the ability of one form of an allele to determine the phenotype of an individual Recessive allele: an allele that is not expressed when in the presence of a dominant allele

Microevolution Change in the frequencies of genotypes in a population

RR RrrR rr R = dominant allele for colorr = recessive allele for color R r Sperm R r Egg

Genetics Homozygous Two dominant or two recessive alleles Heterozygous One dominant and one recessive allele

RR Rr rr Heterozygous dominant Homozygous dominant Homozygous recessive

A gene pool is... all of the genes in a population all of the alleles in a population

Microevolution Change in the frequencies of genotypes in a population

Microevolution Change in the frequencies of genotypes in a population Change in the frequency of alleles in a population

Microevolution Change in the frequencies of genotypes in a population Change in the frequency of alleles in a population Change in the gene pool of a population

Genes are the raw materials of evolution Populations are the essential units that evolve

How do we know if a population is evolving? How do we know if there is change in the frequencies of alleles in a population?

Frequency of an allele in a population # of copies of allele sum of alleles p or q = (for a gene)

Hardy-Weinberg or genetic equilibrium... is a null hypothesis: no change in the frequency of an allele between generations

Simple, discrete trait... Is flower color evolving in this population? RR Rr rr Is there a change in the frequency of flower color alleles in this population?

Frequency of dominant and recessive alleles in a population p + q = 1 p= frequency of dominant allele q= frequency of recessive allele

If the population is at genetic equilibrium, then... 1.Frequency of alleles will remain constant from one generation to the next

If the population is at genetic equilibrium, then... 1.Frequency of alleles will remain constant from one generation to the next 2.This equation predicts the genotype frequencies in the next generation: p 2 + 2pq + q 2 = 1

Frequency of homozygous dominants Frequency of heterozygous dominants Frequency of homozygous recessives

RR RrrR rr R r Sperm R r Egg Parents: p = 0.8q = 0.2 (R) (r)

RR RrrR rr R r Sperm R r Egg Parents: p = 0.8q = 0.2 (R) (r) p=0.8 q=0.2 p=0.8 q=0.2

Sperm Egg Parents: p = 0.8q = 0.2 (R) (r) RR RrrR rr R r R r p=0.8 q=0.2 p=0.8 q=0.2 p 2 =0.64 q 2 =0.04 pq=0.16 qp=0.16

If frequencies of genotypes in the population match p 2 + 2pq + q 2 = 1 then population is at genetic equilibrium-the frequencies of alleles match those of the parent generation. The population is not evolving, at least for the flower color trait we examined

What if.. p 2 + 2pq + q 2 = 0.96 ? RR RrrR rr R r R r p=0.8 q=0.2 p=0.8 q=0.2 p 2 =0.64 q 2 =0.04 pq=0.16 qp=0.16

What factors will throw off genetic equilibrium? Or, what causes populations to evolve?

Microevolution Change in the gene pool of a population

What causes microevolution? 1.Mutation 2.Gene flow 3.Genetic drift 4.Nonrandom mating 5.Natural selection

Critique this cartoon: 1. What is wrong with Bob the dinosaur’s concept of evolution? 2. Is this cartoon funny?