Evolution Final · Visual Cram Sheet · 2-hour everything review

Big Picture · what evolution actually IS

Selection picks people · Evolution moves the population

Diagram · the evolution loop

"Mutation Makes, Selection Sorts, Drift Drifts, Flow Flows."

Background · what counts as evolution

Selection acts on individuals (one organism survives or breeds). Evolution happens to the population (allele frequencies shift between generations). Selection without heritability ≠ evolution.

⭐"V-H-D-F: Variation, Heritable, Differential, Fitness"Darwin's 4 NS requirements. Miss any → no evolution.

⭐"Selection picks PEOPLE; Evolution moves the POPULATION"

Theory ≠ guess. Theory of Evolution sits beside Theory of Gravity — a tested-to-death framework.
— Dobzhansky 1973: "Nothing in biology makes sense except in the light of evolution."

Pre-Darwinian History · who set the stage

Hutton-Lyell-Smith-Cuvier-Lamarck-Malthus → Darwin/Wallace 1858

Diagram · timeline of ideas Darwin needed

Wallace's identical theory (Malay Archipelago, 1858) forced Darwin to publish.

Each thinker · what they contributed

Hutton/Lyell — uniformitarianism, deep time
Smith — stratigraphy, index fossils
Cuvier — confirmed extinction
Lamarck — wrong mechanism, RIGHT that species change
Malthus — populations breed faster than food → struggle
Darwin/Wallace 1858 — joint paper

Key mnemonics

⭐"Malthus made Darwin Mean"Darwin read Malthus 1838 → realized struggle for existence is universal.

⭐"Lamarck = Limbs from Lifting + Legacy"Use & disuse + inheritance of acquired traits. Both wrong. Don't confuse with right-that-species-change.

Trap

⚠ Common TrapLamarck was wrong about mechanism (acquired traits don't inherit) but right that species change. Robbins penalizes "Lamarck was wrong about everything."

📜 WallaceSent Darwin his identical theory from Malay Archipelago 1858. Joint paper at Linnean Society — no priority dispute.

Genome & Mutation · the molecular fuel

Mutation = ONLY source of new variation · Cis-regulatory drives morphology

Diagram · base swap geometry

A↔G and C↔T are transitions (within-class). Anything else is a transversion (cross-class).

Diagram · functional outcomes (codon → protein)

Insertions/deletions not divisible by 3 = frameshift (worst). Single substitutions span the rest.

Diagram · cis-regulatory evolution · Stickleback Pitx1

"Cis-Regulatory Changes Make the Beast." Most morphological evolution = regulatory, not protein.

Background · the human genome

Of ~3 billion bases: ~2% codes for proteins; ~98% is noncoding (regulatory, structural, formerly "junk"). Most morphological differences between species sit in the regulatory 98%.

Mutation	What changes
Point	single base swap
Indel	insertion / deletion
Transition	purine↔purine OR pyrimidine↔pyrimidine — common
Transversion	purine↔pyrimidine — rarer, larger impact

⭐"Cis-Regulatory Changes Make the Beast"Most morphological evolution = REGULATORY, not coding-sequence change.

🔬 Stickleback Pitx1Pelvic-spine loss in freshwater lakes — regulatory change in Pitx1 (enhancer deletion). Same protein, different deployment.

Hardy-Weinberg · the null model

5 conditions hold → frequencies stay flat · break ANY → evolution

Diagram · population-level Punnett

2pq counts BOTH heterozygote squares — that's where the "2" comes from.

Equations · memorize cold

p + q = 1

p² + 2pq + q² = 1

2pq = HETEROZYGOTES

⚠ Trap"2pq = homozygote" → WRONG. 2pq is the HETEROZYGOTE frequency.

⭐"MMSRI"Mutation off · Migration off · Selection off · Random mating · Infinite N. Break ANY → evolution.

Math drill · steps not numbers

Disease frequency = q²
√(q²) = q
p = 1 − q
Carrier frequency = 2pq

🔬 WorkedDisease at 1/10,000 → q² = 0.0001 → q = 0.01 → p ≈ 0.99 → 2pq ≈ 0.02 = 1 in 50 are carriers.

HWE deviation → diagnose mechanism

Pattern	Mechanism
Heterozygote DEFICIT	Inbreeding / assortative mating
Heterozygote EXCESS	Heterozygote advantage (sickle)
Allele freq differs by region	Selection or drift
Small isolated village shifts	Drift
Allele freq matches mainland	Gene flow

Heritability & Breeder's Equation

Big H is whole-genetic · small h is additive-only · only h² predicts response

Diagram · phenotypic variance decomposition

Only h² (narrow / additive) predicts response to selection. Big H does NOT.

Diagram · breeder's equation R = h²S

Realized h² = R/S. Calculated AFTER an experiment by inverting the equation.

Equations · memorize

V_P = V_G + V_E + V_G×E

V_G = V_A + V_D + V_I

H² = V_G/V_P h² = V_A/V_P

R = h² × S · h² ∈ [0,1]

⚠ Trap"Big H predicts response" → WRONG. Only narrow-sense h² (additive) translates to offspring. Dominance & epistasis don't transmit cleanly.

Three Modes of Selection + Frequency-Dependent

Stabilizing squeezes · Directional drives · Disruptive divides

Diagram · the 3 classic modes

"Stabilizing Squeezes · Directional Drives · Disruptive Divides."

Frequency-dependent selection

Negative-FD: rare wins → cycles, maintains polymorphism. Examples: side-blotched lizards (orange/blue/yellow rock-paper-scissors), MHC, prey switching.

Positive-FD: common wins → locks in. Examples: warning coloration, Müllerian mimicry.

⭐"HOT-FV = Balancing"Heterozygote advantage · Negative Frequency-dependence · spatial/temporal Variation. Three sub-types of balancing selection.

Truncation · the breeder's-equation default

Artificial selection: pick a cutoff → every individual above the cutoff breeds. Default for breeder's-equation problems unless told otherwise.

🔬 Sickle-cell trifectaHeterozygote Advantage = Overdominance = Balanced Polymorphism. All synonymous. Robbins switches between them.

Empirical Cases · evolution caught in the act

Fast, real, observed

🔬 Galápagos Finches (Grants)"Dry Drives Deep beaks; Wet welcomes Wee." 1977 drought killed shallow-beaked birds → mean beak depth shifted within ONE generation. Directional selection caught live.

🔬 Peppered Moths (Kettlewell)"Soot Selects Black, Clean returns to Pepper." Industrial melanism — dark form rose with soot, fell when air cleaned.

🔬 Belyaev Foxes"Tame in 50 Generations brings Floppy ears, Spots, Curly tails." Selecting only on tameness pulled along piebald coat, floppy ears, curly tails — pleiotropy of tameness.

🔬 Endler Guppies"Pretty Pools = Pretty Boys; Predator Pools = Plain Boys." Color evolves up/down in 4–14 generations depending on predator presence.

Adaptation · evo-devo + imperfection + exaptation

Tinkering, not engineering · cis-regulatory + heterochrony do most of the work

Diagram · Hox colinearity (gene order = body order)

"Hox Colinearity = Chromosome Order = Body Order." Same logic in flies, mice, humans.

Diagram · Pax6 deep homology

Pax6 transplanted into a fly leg → fly grows an EYE there. → DEEP HOMOLOGY · same toolkit, last shared 540+ MYA "Pax6 Pops Eyes in flies AND mice."

Eyes evolved 40+ times independently — but always with Pax6 as the master switch.

Diagram · eye evolution refutes "irreducible complexity"

Eyes have evolved 40+ times independently across animals.

Diagram · gene duplication → divergence

"Duplicate, Diverge, Discover new function."

Imperfect adaptation · Exaptation · Tiktaalik

⭐"Evolution is a TINKERER, not an ENGINEER" — Jacob

Recurrent laryngeal nerve detour (4 m in giraffe)
Vertebrate retina is INSIDE-OUT → blind spot
Vestigial whale pelvic bones
Wisdom teeth, appendix, narrow human pelvis

Exaptation (Gould)

Trait	Original	Now
Feathers	Insulation/display	Flight
Swim bladder	Lung in early fish	Buoyancy
Middle ear bones	Reptile jaw	Hearing

⭐"Used For X, Now Used For Y"

Tiktaalik (Shubin 2004)

🦴 375 MYA · Ellesmere Is., CanadaPredicted, then found. Phylogeny said "look in mid-Devonian rocks" → wrist bones AND fins. Fish-tetrapod transitional.

Heterochrony: change the pace, change the place. Axolotl = neoteny. Human skull = juvenile ape proportions retained.

Coevolution & Mimicry

Antagonist arms races + mutualist tangos

Antagonist · Red Queen

⭐"Run to Stay in Place" — Van ValenBoth sides evolve perpetually just to maintain fitness. Fitness ≠ stable; the arena moves.

Examples: parasites vs hosts (sex pays for itself this way) · plant-toxin vs insect detox (Ehrlich-Raven escape-and-radiate).

🌿 Geographic mosaicThompson — coevolution has hot spots, cold spots, and trait mixes across geography.

Mimicry · two flavors

Type	Mechanism	Memorize
Batesian	Harmless mimics dangerous (cheats)	BLUFFS
Müllerian	Both dangerous, share warning	MUTUAL

⭐"Bates BLUFFS · Müller MUTUAL"

🌱 Escape-and-RadiatePlant invents poison → bug catches up → cycle. Drives plant-insect diversification.

Sex & Sexual Selection

Anisogamy starts everything · OSR drives ornament size

Why sex pays

⭐"Red Queen + Muller's Ratchet"Sex outruns parasites + recombination purges deleterious mutations that asexual lineages accumulate.

Anisogamy — eggs expensive, sperm cheap → all sex-role asymmetries flow from this.
Bateman's principle — females limited by EGGS; males limited by MATES.

Two arenas of sexual selection

⭐"Intra = Inside same sex (combat) · Inter = Between sexes (choice)"

Intrasexual → antlers, horns, body size (males vs males).
Intersexual → peacock tail, bird song, bowerbird art (female choice).

⭐"Skewed OSR = Strong Selection"Operational Sex Ratio: more receptive males than females → fierce competition → bigger ornaments.

Three hypotheses for female choice (not exclusive)

FISHER RUNAWAYTrait + preference become genetically correlated → both escalate together.

ZAHAVI HANDICAPCostly trait HONEST signal — only good genes can afford it.

HAMILTON-ZUK PARASITESBright = parasite-resistant → choosing him gives offspring resistant genes.

Post-mating: sperm compete; females cryptic-choose (sperm storage, cervical filter, etc.).

Life History · the trade-offs of being alive

High extrinsic mortality → live fast, die young

r vs K

⭐"r = many small (rats)
K = few big (elephants)"

High extrinsic mortality favors r-strategy.

Iter vs Semel

⭐"Iter = REPEAT · Semel = SINGLE shot then die"

Iteroparous: humans, oaks. Semelparous: salmon, agave, octopus, mayfly.

Why we age (3 theories)

⭐"Medawar Hides · Williams Trades · Kirkwood Disposes"Mutation Accumulation · Antagonistic Pleiotropy · Disposable Soma. Senescence is the technical word for aging.

Kin Selection & ESS

Inclusive fitness = direct + indirect · Hamilton's rule

Hamilton's rule

rB > C

r = relatedness · B = benefit to recipient · C = cost to actor.

⭐"r-Big-Bigger-than-C"relatedness × Benefit beats Cost

Relationship	r
Identical twins	1
Full sibs / parent-child	½
Half sibs	¼
Cousins	⅛
HONEYBEE SISTERS	¾

Diagram · haplodiploidy → bee sisters r=¾

100% of dad's allele (A) + 50% of mom's → r = ½(1.0) + ½(0.5) r (sister-to-sister) = 0.75 → MORE RELATED to sisters than to own daughters → STAY & HELP = eusociality

"Haplodiploid Sisters Share Three-Quarters → Sterile Workers."

Diagram · ESS rock-paper-scissors (side-blotched lizards)

"ESS = Strategy that, once common, can't be invaded." — Maynard Smith

Cooperation among non-kin

⭐"Reciprocity, Reputation, Byproduct"

Reciprocity — direct ("you scratch my back…") or indirect (third-party watches)
Reputation — being seen as cooperator pays
Byproduct — both gain incidentally

⚠ TrapGroup selection mostly REJECTED — free-rider problem. Don't fall for "for the good of the species."

Earth's Deep Time

4.5 BYA Earth · 3.8 BYA life · 540 MYA Cambrian

Diagram · Phanerozoic period bar (color-coded)

CAM 540 body plans EXPLODE · DEV 419 age of fish (Tiktaalik 375) · PER 299 Pangaea + Great Dying.

LUCA-Stromatolites-GOE triad

⭐"LUCA Started · Stromatolites Stacked · Oxygen Slaughtered"

LUCA ~3.5–3.8 BYA — Last Universal Common Ancestor
Stromatolites 3.45 BYA — layered cyanobacterial mats
GOE ~2.4 BYA — cyanobacteria pump O₂ → killed anaerobes (1st mass extinction) → enabled eukaryotes

4 Eons · age-of-Earth history

⭐"Hadean Hell · Archean Ancient · Proterozoic Pre-explosion · Phanerozoic Visible"

Kelvin (1862) — capped Earth at ~20 MY (no radioactivity, WRONG)
Holmes 1913 + Patterson 1956 — 4.5 BY via U-Pb on meteorites ✓

Radiometric Dating + Big 5 Extinctions

Cool Kids Usually Rock · O-D-P-Tr-K

Radiometric pairs

Pair	Half-life	Use for
C-14 → N-14	5,730 yr	Recent organics < 50 KY
K-40 → Ar-40	1.3 BY	Volcanic; hominin fossils
U-238 → Pb-206	4.5 BY	Ancient rocks; dinosaurs
Rb-87 → Sr-87	47 BY	Solar-system age

⭐"Cool Kids Usually Rock"C, K, U, Rb (recent → ancient)

⚠ Robbins TrapC-14 CANNOT date dinosaurs. All C-14 gone after ~250 KY. Use U-Pb or K-Ar. "Carbon-14 Can't Catch Cretaceous."

Big 5 mass extinctions

Event	MYA	Cause / loss
Ordovician	445	Glaciation
Devonian	375	Anoxia
Permian	252	96% marine, BIGGEST Siberian Traps
Triassic-J	201	Volcanism
K-Pg	66	76%, dinosaurs Chicxulub asteroid

⚠ TrapPermian was BIGGEST (96%), not K-Pg (76%). K-Pg is the famous one because of dinosaurs.

Phylogeny · reading trees

Synapomorphies define clades · parsimony picks the tree · rotations don't matter

Full 5-vocab set

Term	Meaning
Plesiomorphy	Ancestral character (had it before)
Apomorphy	Derived character (new)
Symplesiomorphy	SHARED ANCESTRAL — useless for clades
Synapomorphy	SHARED DERIVED — defines clades ✓
Autapomorphy	UNIQUE to one taxon — also can't define clade

⭐"Sym-PLES-io = Shared Junk · Syn-APO = Shared Gold · Auto-APO = Solo Quirk"

Clade classes + method

⭐"Mono = Mom + ALL kids ✓ · Para = SOME kids ✗ · Poly = NOT same mom ✗"

⭐"Parsimony = Fewest Flips Wins""Reading trees: Rotations don't matter, only branching." Outgroup roots the tree.

⚠ TrapReptiles WITHOUT birds = paraphyletic. Crocs are closer to birds than to lizards. Sauropsida = the proper monophyletic name.

Homoplasy = convergent / parallel = FALSE phylogenetic signal (bird wing + bat wing).

Species & Speciation

4 concepts · pre/post-zygotic · ASP modes · Haldane's rule

4 species concepts

⭐"BMPE: Best Mammals Play Evens"

Biological (Mayr) — interbreed + reproductively isolated
Morphological — looks
Phylogenetic (Cracraft) — smallest monophyletic clade
Ecological (Van Valen) — niche / adaptive zone

⚠ TrapBSC fails on FAH: Fossils, Asexuals, Hybridizers.

Reproductive isolation

⭐"PRE: HTBMG · POST: ISB"Prezygotic: Habitat, Time, Behavior, Mechanical, Gametic. Postzygotic: Inviability, Sterility, Breakdown.

⭐"Heterogametic Hurts First" — Haldane's RuleHybrid sterile/inviable sex = the heterogametic one (XY males in mammals, ZW females in birds).

Speciation modes

⭐"ASP: Allopatric Apart · Sympatric Same · Parapatric Partly"Allopatric = MOST common.

Polyploidy — Auto = self-doubling · Allo = hybrid + doubling. Instant speciation in plants. ~70% of flowering plants.

⭐"Reinforcement: Hybrids Suck → Don't Date Them → Walls Get Thicker"

Real-time speciation

🍎 Rhagoletis apple maggotSympatric speciation, ~140 ya. Apples introduced ~400 ya, hawthorn flies shifted hosts → mating isolation on host plant.

🌼 Tragopogon goatsbeardAllopolyploidy in Pacific NW, ~80 yrs. Observed in real time.

Biogeography & Adaptive Radiation

MacArthur-Wilson · key innovation opens niches

MacArthur-Wilson (1967)

D₂ = D₁ + originations − extinctions

⭐"BIG + NEAR = MAX SPECIES · SMALL + FAR = FEW"

Larger islands → more species (more niches, lower extinction)
Closer to mainland → more species (higher immigration)
Equilibrium = stable NUMBER, not stable composition

⚠ TrapEquilibrium = same NUMBER, NOT same SPECIES. Turnover continues.

Adaptive radiation

⭐"Empty Niche + Key Innovation + No Competitors"

⭐"Key Innovation = Removes a Constraint, Opens a Niche"NOT "got smarter." E.g., Eleutherodactylus frogs skip tadpole stage → 400+ species.

⭐"Dispersal Jumps · Vicariance Splits"

Conservation Genetics

50/500 rule · Ne < N · extinction vortex

Franklin's 50/500 rule

Ne ≥ 50 short-term — avoid inbreeding depression
Ne ≥ 500 long-term — maintain adaptive variation

⭐"50 to Survive · 500 to Thrive"

⚠ TrapNe is ALWAYS smaller than N. Effective < census because of unequal sex ratio, reproductive variance, bottlenecks.

Real cases

🐆 CheetahSo inbred that skin grafts between unrelated cheetahs are ACCEPTED (no MHC diversity); 70% abnormal sperm.

🐈 Florida panthersRescued by 8 Texas pumas in 1995; fitness restored within a generation.

⭐"Extinction Vortex"Small → Inbreed → Lose Variation → Worse Adaptation → Smaller → 💀

Human Evolution

Bipedal first, big brain later · Lucy settles it

Hominin sequence

⭐"Sahel-Ardi-Australo-Habilis-Erectus-Heidi-Neander-Sapiens"Heidelbergensis (~600 KYA) = common ancestor of Sapiens + Neanderthals + Denisovans.

👩‍🦴 LucyAustralopithecus afarensis · 3.2 MYA, Hadar Ethiopia (1974, Johanson) · 40% complete · bipedal pelvis + chimp-sized brain (~400 cc).

⭐"Bipedalism FIRST, Big Brain LATER"— Lucy settles it.

⭐"Forward Foramen = Forward-walking · Rear Foramen = Four-legged"Foramen magnum position = the single anatomical sign of bipedalism in fossils.

Walking trade-offs (4 B's)

⭐"Walking Wrecks: Back, Birth, Bones, Bulges"

Back pain (lumbar curve, 80% of adults)
Birth difficulty (obstetric dilemma)
Bones wear (knee/hip arthritis)
Bulges (hernias, gravity on abdomen)

⚠ FOXP2 TrapFOXP2 is NOT "the language gene". It's a transcription factor for orofacial motor control — necessary but not sufficient. Functions in non-human animals (songbirds, mice). Robbins penalizes "language gene."

Brain expansion · 3 hypotheses

⭐"Cooking Calories · Social Skills · Survival Smarts"

Cooking (Wrangham) — fire unlocks calories
Social Brain (Dunbar) — group size predicts neocortex
Ecological — foraging / tool problem-solving

Out-of-Africa: H. erectus leaves first (~1.8 MYA); H. sapiens leaves ~60–70 KYA.
Non-Africans: 1–4% Neanderthal · Melanesians/Papuans: 3–6% Denisovan.
EPAS1 high-altitude variant in Tibetans = inherited from Denisovans.
Pääbo, 2022 Nobel — proved Neanderthal interbreeding via ancient DNA.

Tools (4 industries)

Industry	When	Maker
Oldowan	2.6 MYA	H. habilis (flakes)
Acheulean	1.7 MYA	H. erectus (hand-axes)
Mousterian	~300 KYA	Neanderthal (prepared cores)
Upper Paleo	50 KYA	Sapiens (blades, art, projectiles)

⭐"O-A-M-U"

⭐"Looked Modern at 195 KYA · Acted Modern at 70-100 KYA"Anatomical = skeleton; Behavioral = art, symbols, trade. ~100 KY gap.

Evolutionary Medicine

Sickle cell · antibiotic resistance · cancer · FOXP2 trap · p53

Diagram · sickle cell · single nucleotide → whole disease

"Same allele, opposite fitness = environment-dependent selection." Glu6Val single nucleotide swap → whole disease.

Diagram · antibiotic resistance · 4 mechanisms

⚠ Antibiotics DON'T CAUSE mutations — they SELECT pre-existing variants. "Directed mutation" is WRONG.

Nesse's 6 reasons we get sick

#	Reason	Example
1	Pathogens evolve faster	HIV, flu
2	Mismatch (lag)	Obesity, diabetes
3	Trade-offs	Sickle, narrow pelvis
4	Constraints from history	Blind spot, back pain
5	Antagonistic pleiotropy	Testosterone → prostate cancer
6	Apparent disease IS adaptation	Fever, cough, morning sickness

⭐"P-L-T-R-A-A: Pathogens Lag · Trade-offs Restrain · Antagonist Adaptations"

Virulence + hygiene

⭐"Mobile host = Mild bug · Stationary/water host = Vicious bug"Cold (mild, mobile host) vs cholera (deadly, water-borne).

🐰 Myxoma + rabbitsInitial 99.8% kill rate evolved DOWN — dead rabbits = no mosquito feeding. Real-time virulence evolution.

⭐"More Clean = More Allergies, NOT Less"Hygiene hypothesis. No targets → immune system attacks pollen / self.

Cancer = somatic evolution

⭐"Cancer is Darwin Inside You"Heritable variation (somatic mutations) + differential proliferation (selection) = adaptation of the tumor. Drug resistance in tumors mirrors antibiotic resistance.

🛡 p53"Guardian of the Genome." Tumor suppressor with antagonistic-pleiotropy character — prevents cancer early, may accelerate aging late.

Exam-Day Mental File · trap-by-trap

"When Robbins asks WHICH IS NOT — slow down, eliminate one at a time."

If you see…	Answer is…
Mule	Postzygotic / hybrid sterility
C-14 + dinosaur	WRONG — switch to U-Pb or K-Ar
Permian	96%, biggest extinction
K-Pg	76%, dinosaurs, asteroid
"Antibiotics caused"	WRONG — they SELECTED pre-existing variants
Trophy hunting	OPPOSES natural selection
"FOXP2 = language gene"	WRONG — oversimplification
Lamarck	Wrong mechanism, RIGHT that change happens
Reptiles without birds	Paraphyletic, invalid
Anatomical = behavioral modernity	WRONG — ~100 KY gap
"For the good of the species"	Group selection — REJECTED
"Acquired traits inherited"	Lamarck — WRONG
"Big H predicts response"	WRONG — only h² (small h) does
"2pq = homozygote"	WRONG — 2pq = HETEROZYGOTE
"Selection ⇒ Evolution"	WRONG — needs heritability
"a and c" / "all of the above"	Often correct when present

🔥"Every mnemonic · every trap · every lecture · walk in chanting — crush it."