EVOLution · FINAL 2026
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Evolution Study Guide · BIOL 4230

Evolution,
Zimmer & Emlen
— Final.

Teach → test. Read the block, study the diagram, answer the questions. Every prompt is answerable from the passage directly above it — no tricks, just mastery through spaced retrieval.

📅 May 4, 2026 · 5–7 PM · Dr. Travis Robbins 📝 Two-part: Exam 3 (60 pts MC, new material) + Cumulative (60 pts MC + SA) = 120 pts 📚 Chapters 1–18 · 20 lectures
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Exams 1–3 · Evolutionary Biology
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EVOLution · Flashcards · Ch 14
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Term · §14.1
Treadmilling
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Definition
At steady state, actin filaments show net polymerization at the barbed (+) end and net depolymerization at the pointed (−) end — filament length is constant but subunits flow from − to +. Requires continuous ATP hydrolysis.
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EVOLution · Reference Sheet · Exams 1–3 · L01–L20

Hardy-Weinberg · L04

Equation
p² + 2pq + q² = 1 · genotype freq from allele freq
Assumptions (5)
No selection · no drift (∞ N) · no migration · no mutation · random mating
Use
Null model — deviation flags one of the 5 forces
q from rare recessive
q ≈ √(disease freq); carriers ≈ 2pq
X-linked
Males: q · Females: q² — disease much more common in ♂

Forces of evolution

Selection
Differential reproduction by phenotype · adaptive · directional
Drift
Random allele freq change · stronger in small N · non-adaptive
Gene flow
Migration homogenizes populations · counters local adaptation
Mutation
Source of all variation · ~10⁻⁸/site/gen · weak alone
Non-random mating
Inbreeding ↑ homozygosity (no Δp) · assortative skews genotypes

Selection types · L05–L07

Directional
Mean shifts; one tail favored (peppered moth, Galápagos beaks)
Stabilizing
Mean steady, variance ↓ (birth weight)
Disruptive
Both tails favored, variance ↑ (can drive sympatric speciation)
Breeder's eq
R = h²S · response = heritability × selection differential
Sexual sel
Differential mating success — runs counter to natural sel

Drift & effective N · L04

Fixation prob
New neutral allele = 1/(2N) · time to fix ≈ 4N gens
Bottleneck
Crash → drift dominates → ↓ heterozygosity (cheetah, N. elephant seal)
Founder effect
Few colonists → non-random sample of source pool
FST
0 = panmictic · 0.05–0.15 moderate · >0.25 very structured
Coalescence
Trace lineages back to MRCA; T̄ ≈ 4Nₑ for autosomes

Sexual selection · L11

Anisogamy
Unequal gametes → ♀ choosy, ♂ competitive (Bateman)
Intrasexual
Same-sex contest — armaments, body size (elk, elephant seals)
Intersexual
Mate choice — ornaments (peacock tail, bird song)
Runaway (Fisher)
Trait + preference genetically correlated → exponential elaboration
Good genes / handicap
Costly signal honest if only fit males can bear it (Zahavi)
Sexual conflict
Evol. interests differ between sexes — antagonistic coevolution

Phylogenetics · L15

Monophyletic
Ancestor + all descendants — only valid clade
Paraphyletic
Ancestor + some descendants (Reptilia w/o birds) · invalid
Polyphyletic
Multiple origins (e.g. "warm-blooded") · convergent
Synapomorphy
Shared derived trait — defines a clade
Parsimony / ML
Fewest changes · highest likelihood under substitution model
Molecular clock
~constant rate → divergence time; calibrate with fossils

Speciation · L16–L18

BSC (Mayr)
Interbreeding pops reproductively isolated · fails for asexuals/fossils
Allopatric
Geographic barrier → vicariance or peripatric (most common mode)
Sympatric
No barrier — disruptive sel, polyploidy (apple maggot fly)
Prezygotic
Habitat · temporal · behavioral · mechanical · gametic
Postzygotic
Hybrid inviable / sterile / breakdown F2 (mule, Haldane's rule)
Reinforcement
Sel against hybrids strengthens prezygotic isolation in sympatry

History of life · L13–L14

~3.8 GYA
LUCA · prokaryotes · RNA-world precursors
~2.4 GYA
GOE — cyanobacteria oxygenate atmosphere
~2.1–1.6 GYA
Eukaryotes — α-proteobacterial mitochondria
~540 MYA
Cambrian explosion — most animal phyla appear
Big Five
Ord-Sil · Late Dev · End-Permian (96%) · End-Tri · K-Pg (dinos)
Endosymbiosis
Mito ← α-proteo · plastids ← cyanobacteria (1° & 2°)

Coevolution & medicine · L09, L20

Mutualism
Both gain (pollinators, mycorrhizae); cheaters punished
Red Queen
Host-parasite arms race — must keep evolving to stay even
Antibiotic R
Strong + recent selection · pre-existing variation · HGT spreads
Mismatch
Modern environment ≠ EEA (obesity, myopia, autoimmune)
Proximate vs ultimate
HOW mechanism vs WHY adaptive — Tinbergen's distinction
Inclusive fitness
Hamilton: rB > C · explains kin-directed altruism (L12)
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