The process of evolution drives the diversity and unity of life.

BIG IDEA #1

Natural selection acts on phenotypic variations in populations Sources of variation:

Mutation Random assortment during meiosis Crossing Over Random Fertilization Diploidy

Allele Frequencies can be altered by: Gene Flow: Immigration and Emigration Genetic Drift: small populations Mating Patterns: Inbreeding and Sexual Selection

MECHANISMS OF VARIATION

Stabilizing Selection: favors intermediate phenotype (heterozygote advantage)

Directional Selection: favors one extreme over another

Disruptive Selection: favors both extremes over the intermediate

TYPES OF SELECTION

Campbell, Neil A. Reece; Jane B., BIOLOGY, 6th Edition 2002

Convergent Evolution: two dissimilar populations evolve similar traits b/c of similar selective pressures. Ex: dolphin and shark

Parallel Evolution: similar to convergent however, organisms do not need to occupy the same niches. Ex: warning colors of many organisms

Divergent Evolution: organisms from a common ancestor become less similar (adaptive radiation) Ex: Galapagos Tortois

PATTERNS OF EVOLUTION

DNAAmino acid sequence/similar proteinsAnalogous structuresVestigial structuresHomologous structures

EVIDENCE FOR EVOLUTION

Large populationRandom matingNo mutationsNo gene flowNo natural selection

CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM

Frequency of dominant allele if frequency of recessive allele is given p if q is given

Frequency of recessive allele if the % of the population with the recessive phenotype is given q if q2 is given

Calculate the % of the population with recessive allele if the % of the population expressing the dominant allele is given q2 if p2+2pq

DETERMINING ALLELE FREQUENCIES

Speciation occurs when populations accumulate enough changes over time to lead to the emergence of a new species.

Types: Allopatric—geographic

barriers Sympatric—reproductive

barriers Polyploidy in plants leads

to new species b/c the polyploids can not breed with the diploid ancestors

SPECIATION

Prezygotic Isolating Mechanisms: Geographic (Habitat) Isolation Ecological Isolation Behavioral Isolation Temporal Isolation Mechanical Isolation Sexual Isolation

Postzygotic Isolating Mechanisms: Hybrid Sterility Hybrid Inviability Zygote Mortality

MECHANISMS FOR REPRODUCTIVE ISOLATION

PRE AND POST ZYGOTIC MECHANISMS FOR REPRODUCTIVE

ISOLATION

Miller and Urey’s Experiment Amino acid monomers, polymers, protobiont, first cells

Characteristics of the First Cells Unicellular Heterotrophic Prokaryotic Simple lipid membrane Ribosomes RNA

Autotrophic prokaryotes would appear soon after

ORIGINS OF LIFE

Theory of Endosymbiosis—Large eukaryotic cells evolved when a small prokaryotic cells was engulfed by a larger prokaryotic cell and they developed a symbiotic relationship where both benefi tted. Smaller one eventually

evolves into mitochondria (in heterotrophs) or chloroplasts (in autotrophs).

Evidence: Mitochondria and Chloroplasts have their own DNA and ribosomes. They are about the size of prokaryotes. Their membranes are similar to prokaryotes.

ORIGINS OF COMPLEX CELLS

Three Domains Bacteria Archae Eukarya

Six Kingdoms Eubacteria Archaebacteria Protista Fungi Plantae Animalia

DIVERSITY OF LIFE

Cladograms show relative relatedness between a group of organisms

CLADOGRAMS