Oh hell no

When did Earth form?

4.6 billion years ago, from accretion of dust and gas in the solar nebula.

What are stromatolites?

Layered structures formed by cyanobacteria (prokaryotes); first fossils 3.5 BYA.

What is the significance of stromatolites?

Earliest evidence of life; contributed to oxygenation of atmosphere.

Name the 4 stages of life evolution.

1) Abiotic synthesis, 2) Polymer formation, 3) Protocells, 4) Self-replicating molecules.

Abiotic synthesis

Formation of small organic molecules naturally without life; proposed by Oparin & Haldane (1920).

Why was early Earth suitable for abiotic synthesis?

Low oxygen atmosphere allowed bonds to form without interference.

Miller-Urey Experiment (1953)

Simulated early Earth’s gases (H2, CH4, NH3, H2O) + electric sparks → produced amino acids.

What did Miller-Urey demonstrate?

Organic molecules necessary for life could form from inorganic compounds.

Reproducibility of Miller-Urey experiment

Repeated multiple times; produced all 20 amino acids and other building blocks of life.

Extraterrestrial hypothesis

Life or its building blocks arrived on Earth via meteorites.

Evidence for extraterrestrial origin

Amino acids and organic compounds found in some meteorites.

Deep hydrothermal vent hypothesis

Life originated near mineral-rich underwater vents with heat and chemical energy.

Polymer formation

Monomers link to form macromolecules like proteins, nucleic acids.

Sidney Fox contribution

Hot sand, clay, and rocks can catalyze amino acids forming polymers.

Protocells

Membrane-bound sacs formed spontaneously from lipids in water, encapsulating molecules.

Importance of protocells

Precursor to living cells; could maintain internal environment.

Self-replicating molecules

RNA molecules that can act as templates to produce complementary RNA strands.

Ribozymes

RNA molecules that can catalyze chemical reactions like enzymes.

RNA World Hypothesis

Life may have started with RNA capable of both storing genetic information and catalysis.

Transition from RNA to DNA

DNA is more stable; RNA gradually gave rise to DNA as main hereditary material.
FOSSILS & DATING METHODS

Macroevolution

Large-scale evolutionary changes above species level, including speciation and mass extinctions.

Fossil definition

Preserved remains or impressions of ancient organisms in rock.

Radiometric dating

Measures decay of radioactive isotopes to determine absolute age of rocks/fossils.

Half-life definition

Time required for 50% of a radioactive isotope to decay.

Carbon-14 half-life

5,730 years; useful for dating recent fossils.

Potassium-40 half-life

1.3 billion years; used for older rocks/fossils.

Relative dating

Determines fossil age based on position in sedimentary layers.

Strata

Layers of sedimentary rock; older layers below, newer above.

Geologic record

Timeline of Earth’s history divided into Eons → Eras → Periods.

Phanerozoic Eon

Current eon; includes Cenozoic, Mesozoic, Paleozoic eras.

Cenozoic Era

66 MYA – present; includes Quaternary (1.6 MYA) and Tertiary (66 MYA).

Mesozoic Era

250 – 66 MYA; includes Triassic, Jurassic, Cretaceous.

Paleozoic Era

570 – 250 MYA; includes Cambrian → Permian periods.

Proterozoic Eon

2.5 – 0.54 BYA; before complex multicellular life.

Significance of fossil record

Shows sequence of life forms and evolutionary trends over time.

Transitional fossils

Fossils showing intermediate traits between ancestral and derived species.

Index fossils

Species that existed for a short time but had wide geographic distribution; used to date rock layers.

Fossilization processes

Permineralization, casts & molds, amber preservation, freezing.

Radiometric dating vs relative dating

Radiometric = absolute age; relative = age relative to surrounding strata.

Importance of half-life in dating

Determines rate at which isotopes decay, allowing calculation of rock age.
PLATE TECTONICS & EXTINCTIONS

Continental drift

Movement of Earth’s plates on molten magma; causes earthquakes, mountains, volcanoes.

Pangea

Supercontinent formed ~150 MYA; breakup influenced species distribution.

Mass extinction

Rapid global environmental changes killing >50% of species; recovery takes millions of years.

Permian extinction

252 MYA; linked to massive volcanic activity → largest known mass extinction.

Cretaceous extinction

66 MYA; asteroid impact → wiped out dinosaurs.

5 major extinctions

Ordovician, Devonian, Permian, Triassic, Cretaceous; humans may be causing a 6th.

Adaptive radiation

Rapid evolution of multiple species from a single ancestor to occupy new niches.

Examples of adaptive radiation

Darwin’s finches in Galápagos, cichlid fish in African lakes.

Effect of plate tectonics on evolution

Alters habitats, creates barriers, isolates populations → speciation.

Mountains & evolution

Formed by plate collisions → new habitats and evolutionary pressures.
EVO-DEVO & DEVELOPMENT

Evo-devo

Combines evolutionary and developmental biology; studies how developmental genes influence evolution.

Homeotic genes

Master genes controlling body plan and development (e.g., Hox genes).

Exaptation

Trait evolved for one function but co-opted for another (e.g., feathers for flight).

Evolutionary trends

Patterns in anatomy or function; do not imply ultimate goal.

Changes in developmental genes

Can alter number, placement, or sequence of body parts → morphological diversity.

Hox gene significance

Controls anterior-posterior axis in animals; mutations → homeotic transformations.

Example of exaptation

Feathers: initially for insulation → later used for flight.

Importance of evo-devo

Explains origin of complex structures from simple genetic changes.

Relationship between evo-devo and macroevolution

Developmental changes can produce major evolutionary innovations.

Master control genes

Genes that regulate other genes to organize body structures.
PHYLOGENY & TAXONOMY

Phylogeny

Evolutionary history and relationships among species.

Taxonomy

Science of classifying organisms.

Binomial nomenclature

Two-part scientific name: Genus + species epithet (e.g., Homo sapiens).

Taxonomic hierarchy

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
Mnemonic: Dear King Phillip Came Over For Good Soup

Systematics

Classification based on evolutionary relationships.

Phylogenetic tree

Diagram showing hypothesized evolutionary relationships among species.

Cladistics

Groups species by common ancestor (monophyletic clade).

Shared ancestral character

Trait found in a clade but originated earlier than the clade’s ancestor.

Shared derived character

Trait present in clade members but not in distant ancestors.

Convergent evolution

Independent evolution of similar traits in unrelated species due to similar environments.

Molecular systematics

Uses DNA, RNA, or proteins to infer evolutionary relationships.

Molecular clock

Estimates divergence times based on DNA mutation rates.

Horizontal gene transfer

Direct transfer of genes between organisms, common in bacteria.

Analogy

Similar structure with similar function, not from common ancestry (e.g., wings of bats and insects).

Homology

Structures from common ancestor (e.g., vertebrate forelimb bones

Cambrian Period

570–500 MYA; explosion of diverse marine life (“Cambrian Explosion”).

Ordovician Period

500–435 MYA; first vertebrates appear; first mass extinction at end due to glaciation.

Silurian Period

435–410 MYA; first vascular plants; first terrestrial arthropods.

Devonian Period

410–360 MYA; “Age of Fishes”; first amphibians; first insects on land.

Mississippian Period

360–330 MYA; expansion of amphibians; coal-forming forests.

Pennsylvanian Period

330–290 MYA; first reptiles; extensive swamp forests.

Permian Period

290–250 MYA; formation of Pangea; Permian mass extinction (~90–95% species lost).

Triassic Period

240–205 MYA; first dinosaurs and mammals appear.

Jurassic Period

205–138 MYA; large dinosaurs dominate; first birds (Archaeopteryx).

Cretaceous Period

138–66 MYA; flowering plants appear; ends with asteroid-driven mass extinction.

Tertiary Period

66–1.6 MYA; mammals diversify; modern birds; early hominins appear.

Quaternary Period

1.6 MYA–present; Ice Ages; humans evolve.
SCIENTISTS & EXPERIMENTS

Oparin/Haldane hypothesis

1920s; early Earth atmosphere lacked oxygen → allowed organic molecules to form spontaneously.

Miller-Urey apparatus

Simulated ocean + atmosphere + lightning; produced amino acids.

Sidney Fox experiments

Heated amino acids on hot sand, clay, and rock → formed “proteinoid microspheres” (early polymers).

Ribozyme discovery

RNA molecules capable of catalyzing reactions; proves RNA can store information and act enzymatically.

Significance of RNA world hypothesis

Explains how life could start without DNA/protein enzymes.

Evidence supporting deep-sea vent hypothesis

Rich minerals + chemical gradients could drive prebiotic chemistry; unique microbes exist in vents today.
MACROEVOLUTION DETAILS

Definition of speciation

Formation of new species from ancestral species, often through reproductive isolation.

Types of speciation

Allopatric (geographic isolation), Sympatric (same area, ecological or behavioral isolation).

Adaptive radiation definition

Rapid evolution of many species from one ancestor to exploit ecological niches.

Example of adaptive radiation

Darwin’s finches: different beak shapes evolved for different food sources.

Mass extinction impact

Removes dominant species → allows diversification of surviving lineages.

Recovery from mass extinction

Usually takes 5–10 million years to regain biodiversity.