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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
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