Unit 10 — Adaptations and Evolution

Unit 10: Need to Know and Be Able to Do

10.1 - Chemical vs. Organic Evolution

Learning goals

Define chemical evolution (inorganic → organic molecules, nothing alive) and organic evolution (change in living things, starting with the first cells)
Describe the early atmosphere — no free O₂
Explain the Miller–Urey result: inorganic gases + energy → amino acids
Sequence inorganic molecules → organic molecules → basic cells → major nutritional strategies
Explain why photosynthetic autotrophs had to come before aerobic heterotrophs (they made the O₂)
Sequence the endosymbiotic theory: prokaryote → nucleus → aerobic bacterium (mitochondria) → photosynthetic bacterium (chloroplast)
Identify cell types: nucleus only or nucleus + mitochondria = heterotrophic eukaryote; + chloroplast = autotrophic eukaryote
Cite evidence for endosymbiosis: own DNA, own ribosomes, two membranes, divide on their own
Name cyanobacteria as the first O₂ producers; order anaerobic heterotrophs → photosynthetic autotrophs → aerobic heterotrophs; use the class terms circular DNA and binary fission for the evidence
Order the endosymbiosis images
Complete the heterotroph/autotroph model: inorganic → organic → basic cells, then oxygen structures → aerobic heterotrophs and light structures → photosynthetic autotrophs
Identify each cell in an endosymbiosis diagram

10.2 - Darwin's Four Forces

Learning goals

Name the four forces: overproduction, genetic variation, competition, unequal reproductive success. The standard lists them in no fixed order, and your class notes put variation first. What is fixed is that unequal reproductive success comes after competition, and the trait spreading is the result
Identify overproduction from a stem that stresses how many offspring are made vs. how few survive
Identify genetic variation as inherited differences within one species
Explain competition as a struggle for limited resources (food, water, space, mates)
Define fitness as the number of surviving offspring — not size, strength or lifespan
State that individuals are selected; populations evolve
State that acquired traits are not inherited and organisms do not change because they need to
Explain that mutation is the source of new variation and that selection only chooses among existing variants
Pick sea turtles laying ~100 eggs (overproduction) and fox squirrel coat colors (variation) as driving forces
Predict that the better competitor (species B) will survive and pass on its traits
Identify natural selection due to predation as the cause of the moth frequency change

10.3 - Natural Selection in a Changing Environment

Learning goals

Run the four-move loop on any scenario: what changed → which variant matches → it survives and reproduces → its frequency rises
Explain the peppered moth before, during and after the Industrial Revolution
Choose the graph for any direction: dark moths during (rises), light moths during (falls), dark moths after clean-air laws (falls), no selection (flat). Read the time window first
Read and choose a frequency-over-time graph — rising during the Industrial Revolution, falling after clean-air laws
Define genetic frequency as a proportion of the population
Read a before/after trait graph: one end favored, the curve shifts; middle favored, taller and narrower; both ends favored, two peaks. The names (directional, stabilizing, disruptive) are class vocabulary, not test vocabulary. 2026 Q5 is the one-end shift in table form
Interpret simulation data (bead hunt) and predict the result on a new background
Explain antibiotic / pesticide resistance as selection on variation already present
Distinguish an adaptation (inherited) from an acquired trait
Choose the graph that rises for dark-colored moth frequency during the Industrial Revolution
Predict that dark-brown mice will continue to increase if the soil stays dark
Explain a rabbit fur-color shift as the visible variant being reduced by predators while the other reaches adulthood to reproduce
Explain creosote toxins as decreasing competition and increasing the bushes' ability to reproduce

10.4 - Speciation

Learning goals

Define a species by interbreeding and fertile offspring, not by appearance or location
Define gene flow and explain why stopping it allows populations to diverge
Sequence speciation: barrier → no gene flow → different changes → reproductive isolation
Distinguish geographic, behavioral and temporal isolation, and reproductive isolation as the result
Recognize inability to interbreed as the proof that speciation has occurred
Deer split by a flood waterway: certain genes became more dominant within each population — 2026 Q25 (on this item "more dominant" means more common)
Grand Canyon squirrels: Process: speciation, split by the canyon, each adapting
Ensatina: southward movement into drier, warmer environments turned one subspecies into at least two
Rice's whale: geographic isolation → reduced gene flow → genetic differences and food preferences

10.5 - Evidence of Common Ancestry

Learning goals

Name the five lines of evidence: comparative anatomy · embryology · fossil record · molecular (DNA/protein) · biogeography
Identify homologous structures (same bones, different jobs) as evidence of common ancestry
Reject analogous structures (same job, different build) as evidence of common ancestry
Identify vestigial structures as reduced leftovers from an ancestor
Explain why early vertebrate embryos (pharyngeal pouches, tail) point to a shared ancestor
Use rock layers: undisturbed, deeper = older
Rank relatedness from a protein or DNA difference table: fewer differences = more recent common ancestor
Explain biogeography: close relatives live near each other (Galápagos finches ↔ South America)
Identify genetic data and anatomical/morphological data as the strongest evidence
Horse fossils: height increased, toes decreased
Horse fossils: toe 3 had the most impact
Rice's whale: genetic code · anatomy and morphology · biogeographic distribution

10.6a - Reading a Cladogram

Learning goals

Label root, node, branch, tip and derived-trait hash mark
State that every tip above a hash mark has that trait
Find the most recent common ancestor by tracing two tips down to where they meet
Decide which two are most closely related from the shared node, not from tip position
Recognize that rotating branches does not change relationships
Use outgroup (branches off first), sister taxa (share the most recent node) and clade (an ancestor and all its descendants). Say "branched off first," not "oldest organism"
Reject "X evolved from the tip beside it" and "the right side is more evolved"
Trait separating salmon from the others = development of lungs
Trait separating lizards from hamsters and chimpanzees = fur and mammary glands
Place insects, fish, amphibians, prosimians on a trait-labeled cladogram with birds given

10.6b - Building Trees from a Character Table

Learning goals

Read a present/absent character table
Count down each trait column: most X's = oldest, lowest on the tree
Count across each organism row: fewest X's = branches off first
Place a trait shared by all on the root
Choose the two most closely related organisms by most shared derived traits
Order plant traits chlorophyll a and b → vascular tissue → seeds → flowers
State that the lowest trait on a cladogram is the oldest