Evolution, Diversity, Classification — Practice Quiz

A Biology cheat sheet for Evolution, Diversity, Classification — every key formula with its symbols defined — plus a medium-level practice quiz to test recall.

Formulas & key concepts

Darwin + Wallace: <b>Descent with Modification</b>. <b>Variation</b> (heritable traits differ), <b>Struggle for Existence</b> (limited resources), <b>Survival of the Fittest</b> (differential reproduction). Leads to <b>Adaptation</b> over generations.

Natural Selection & Darwin's Theory
Fossil Record: Preserved remains show Intermediate Forms (transitional species, e.g., Archaeopteryx). Relative Dating (rock layers), Radiometric Dating (isotopes). Index Fossils identify time periods.
Evidence: Fossils
Homologous Structures: Same structure, different function (bat wing vs. human arm = common ancestry). Vestigial Structures: Reduced/nonfunctional remnants (human appendix, whale pelvis). Analogous Structures: Similar function, different origin (bat vs. insect wing = convergent evolution).
Evidence: Comparative Anatomy

Geographic distribution reflects evolutionary history. <b>Island Species</b> (Galápagos finches). <b>Continental Drift</b> (fossils on separate continents, e.g., Mesosaurus).

Evidence: Biogeography
Embryological Similarities: Early development stages similar across species. Molecular Homologies: DNA/Protein sequences reveal relatedness (more similar = more recent common ancestor).
Evidence: Embryology & Molecular Biology

Discredited theory: Traits acquired during lifetime passed to offspring (giraffes stretching necks). <b>Incorrect</b> because only genetic changes inherited.

Lamarck & Inheritance of Acquired Characteristics

Integration of Darwin's natural selection + Mendelian genetics + population genetics. Evolution = change in <b>allele frequencies</b> over time.

Modern Synthesis
Divergent: Common ancestor → different forms (adaptive radiation, e.g., Darwin's finches). Convergent: Distantly related → similar forms (analogous structures, e.g., shark vs. dolphin streamlining).
Divergent vs. Convergent Evolution
Gene Pool: All alleles in a population. Population Genetics: Study of allele frequency changes. Evolution = change in allele frequencies over generations.
Gene Pool & Allele Frequency
No evolution if: Large population, Random mating, No mutations, No migration, No natural selection. Equations: p + q = 1 (alleles), p² + 2pq + q² = 1 (genotypes).
Hardy-Weinberg Equilibrium
Directional (one extreme favored), Stabilizing (average favored), Disruptive (both extremes favored). Sexual Selection: Traits for mating success.
Natural Selection (Types)

Random changes in allele frequencies (smaller populations = greater effect). <b>Bottleneck Effect</b>: Population crash reduces diversity. <b>Founder Effect</b>: Small group colonizes new area with unrepresentative alleles.

Genetic Drift

Movement of alleles between populations via migration. <b>Increases</b> genetic diversity within populations, <b>decreases</b> differences between populations.

Gene Flow (Migration)

Ultimate source of new alleles. Can be beneficial, neutral, or harmful. <b>Point Mutations</b> (single nucleotide), <b>Chromosomal Mutations</b> (large-scale changes).

Mutation
Microevolution: Small-scale changes within a population (allele frequency shifts). Macroevolution: Large-scale patterns over geological time (speciation, mass extinctions, adaptive radiation).
Microevolution vs. Macroevolution

Formation of new species when populations can no longer interbreed. <b>Reproductive Isolation</b> (Prezygotic: Behavioral, Temporal, Geographic barriers; Postzygotic: Hybrid inviability/sterility).

Speciation & Reproductive Isolation

Geographic separation prevents gene flow. <b>Vicariance</b> (barrier divides population), <b>Dispersal</b> (colonization of new area). Example: Darwin's finches.

Allopatric Speciation

Speciation without geographic separation. <b>Polyploidy</b> (extra chromosome sets, common in plants), <b>Behavioral/Sexual Selection</b> isolation.

Sympatric Speciation
Adaptive Radiation: Rapid diversification from common ancestor to fill niches (e.g., Hawaiian honeycreepers). Coevolution: Reciprocal evolutionary changes between interacting species (flowers ↔ pollinators).
Adaptive Radiation & Coevolution
Taxonomy: Science of naming/classifying organisms. Binomial Nomenclature: Genus + species (e.g., Homo sapiens). Hierarchy: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.
Taxonomy & Linnaean Classification
Domains: Bacteria (peptidoglycan cell walls), Archaea (extremophiles, unique lipids), Eukarya (membrane-bound nucleus). Six Kingdoms: Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia.
Three Domains & Six Kingdoms
Phylogeny: Evolutionary history. Phylogenetic Tree: Diagram showing relationships. Branch Points (common ancestors), Sister Taxa (share recent ancestor), Rooted Tree (single common ancestor).
Phylogeny & Phylogenetic Trees
Cladistics: Classification by shared Derived Characters (evolutionary novelties). Clade (Monophyletic Group): Ancestor + all descendants. Maximum Parsimony: Simplest evolutionary explanation preferred.
Cladistics & Clades
Homologous: Inherited from common ancestor (indicates relatedness). Analogous: Similar due to convergent evolution (does NOT indicate relatedness).
Homologous vs. Analogous (Classification)

DNA/protein sequences used to determine relationships. More similar sequences = more closely related. <b>Molecular Clocks</b> estimate divergence times.

Molecular Systematics
Eons: Hadean, Archean, Proterozoic, Phanerozoic. Eras: Paleozoic, Mesozoic, Cenozoic. Periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, Quaternary.
Geologic Time Scale
Miller-Urey Experiment: Organic molecules from inorganic precursors (simulated early Earth atmosphere). Primordial Soup Hypothesis. RNA World: Self-replicating RNA preceded DNA/proteins.
Origin of Life
Mitochondria and Chloroplasts originated from engulfed prokaryotes. Evidence: Own DNA, double membrane, binary fission, ribosomes similar to bacteria.
Endosymbiotic Theory
Permian (~251 mya, 96% species lost), Cretaceous (~66 mya, dinosaurs extinct). Causes: Asteroid Impacts, volcanic eruptions, climate change. Lead to Adaptive Radiation of survivors.
Mass Extinctions
Cambrian Explosion (rapid diversification ~540 mya), Colonization of Land (plants → arthropods → vertebrates), Evolution of Flight (insects, pterosaurs, birds, bats).
Major Evolutionary Events
Prokaryotes: No nucleus. Peptidoglycan cell walls. Shapes: Cocci (spheres), Bacilli (rods), Spirilla (spirals). Gram Staining: Gram+ (thick peptidoglycan), Gram- (thin + outer membrane). Cyanobacteria: Photosynthetic, oxygenated atmosphere.
Bacteria (Domain Bacteria)
Extremophiles: Thermophiles (hot springs), Halophiles (salt lakes), Methanogens (produce methane). Pseudopeptidoglycan cell walls. More similar to Eukarya than Bacteria (genetics).
Archaea (Domain Archaea)
Decomposers, Nitrogen Fixation, Pathogens (disease). Biofilms: Communities in sticky matrix. Horizontal Gene Transfer: Conjugation (pilus), Transformation (uptake DNA), Transduction (virus).
Prokaryote Ecology & Processes

Diverse eukaryotes. <b>Supergroups</b>: Excavata (Giardia), Chromalveolata (diatoms, brown algae), Rhizaria (forams), Archaeplastida (red/green algae), Amoebozoa (amoebas, slime molds), Opisthokonta (ancestors of fungi/animals). <b>Protozoa</b> (animal-like), <b>Algae</b> (plant-like), <b>Slime Molds</b> (fungus-like).

Protists (Kingdom Protista)
Heterotrophs (absorb nutrients). Chitin cell walls. Hyphae (filaments) form Mycelium (mass). Saprobes (decompose dead matter). Spores for reproduction.
Fungi Characteristics
Chytridiomycota (aquatic, flagellated spores), Zygomycota (bread mold), Ascomycota (sac fungi, yeasts, morels), Basidiomycota (club fungi, mushrooms), Glomeromycota (mycorrhizae).
Fungi Diversity
Lichens: Fungus + photosynthetic partner (alga/cyanobacteria). Mycorrhizae: Fungus + plant roots (nutrient exchange). Pathogens: Mycoses (fungal infections), crop diseases.
Fungi Symbioses
Cuticle (waxy layer prevents water loss), Stomata (gas exchange pores), Vascular Tissue (Xylem: water/minerals up, Phloem: sugars down), Roots (anchor + absorb), Alternation of Generations (Sporophyte 2N ↔ Gametophyte N).
Plant Adaptations to Land
Mosses, Liverworts, Hornworts. No vascular tissue (small size, moist habitats). Gametophyte-dominant. Sperm require water for fertilization.
Nonvascular Plants (Bryophytes)
Club Mosses, Horsetails, Ferns, Whisk Ferns. Vascular tissue (larger than bryophytes). Sporophyte-dominant. Reproduce via spores. Still require water for fertilization.
Seedless Vascular Plants
Conifers (pines, spruces), Cycads, Ginkgo, Gnetophytes. Seeds in cones (not enclosed). Heterosporous (megaspores → female, microspores → male). Pollen (no water needed for fertilization).
Gymnosperms (Naked Seeds)
Flowers: Sepals, Petals, Stamens (male: anther + filament), Carpel/Pistil (female: stigma, style, ovary). Fruit (mature ovary) protects/disperses seeds. Monocots (1 cotyledon, parallel veins) vs. Eudicots (2 cotyledons, netted veins).
Angiosperms (Flowering Plants)
Symmetry: Asymmetrical (sponges), Radial (cnidarians), Bilateral (most animals). Germ Layers: Diploblasts (2 layers: ectoderm + endoderm), Triploblasts (3 layers: + mesoderm). Coelom: Acoelomates (no cavity), Pseudocoelomates (partial cavity), Eucoelomates (true coelom). Development: Protostomes (mouth first) vs. Deuterostomes (anus first).
Animal Body Plans
Porifera (Sponges): Asymmetrical, no tissues. Choanocytes (collar cells filter food), Spicules (support). Cnidaria: Radial symmetry, diploblasts. Cnidocytes (stinging cells), Nematocysts (harpoons). Polyp (sessile) vs. Medusa (free-swimming). Classes: Hydrozoa, Scyphozoa (jellyfish), Cubozoa (box jellies), Anthozoa (corals, anemones).
Sponges & Cnidarians
Platyhelminthes (Flatworms): Acoelomates, bilateral. Turbellaria (planarians), Trematoda (flukes), Cestoda (tapeworms), Monogenea. Nematoda (Roundworms): Pseudocoelomates, complete digestive system, cuticle. Annelida: True coelomates, Metamerism (segmentation), Chaetae (bristles). Classes: Polychaeta, Oligochaeta (earthworms), Hirudinea (leeches).
Worms: Flatworms, Roundworms, Annelids
Mollusca: Mantle (secretes shell), Radula (scraping tongue), Ctenidia (gills). Classes: Gastropoda (snails), Bivalvia (clams), Cephalopoda (squid, octopus). Echinodermata: Radial symmetry (adults), Water Vascular System, Endoskeleton with spines. Deuterostomes. Classes: Asteroidea (sea stars), Echinoidea (sea urchins), Holothuroidea (sea cucumbers).
Mollusks & Echinoderms
Jointed Appendages, Segmentation, Exoskeleton (chitin), Molting. Hemocoel (open circulatory system). Subphyla: Chelicerata (spiders, scorpions), Myriapoda (millipedes, centipedes), Hexapoda (insects: 3 body segments, 6 legs, wings), Crustacea (crabs, lobsters, barnacles).
Arthropods
Chordata: Notochord, Dorsal Hollow Nerve Cord, Pharyngeal Slits, Post-Anal Tail (at some life stage). Subphyla: Cephalochordata (lancelets), Urochordata (tunicates), Vertebrata (vertebral column replaces notochord).
Chordates & Vertebrate Characteristics
Agnatha (jawless: lampreys, hagfish). Chondrichthyes (cartilaginous: sharks, rays; Ampulla of Lorenzini, placoid scales). Osteichthyes (bony fish): Actinopterygii (ray-finned), Sarcopterygii (lobe-finned, ancestors of tetrapods). Swim Bladder, Lateral Line, Operculum.
Fish
Amphibia: Dual life (aquatic larvae → terrestrial adults). Cutaneous Respiration (skin breathing), moist skin. Metamorphosis. Orders: Anura (frogs/toads), Urodela (salamanders), Apoda (caecilians). First vertebrates on land.
Amphibians
Reptilia: Amniotic Egg (shell + membranes), Scales (keratin), Ectotherms. Orders: Testudines (turtles), Squamata (lizards, snakes), Crocodilia (crocodiles, alligators), Sphenodontia (tuatara). Aves (Birds): Endotherms, Feathers, Pneumatic Bones (hollow), One-Way Air Flow, Down Feathers (insulation). Evolved from theropod dinosaurs.
Reptiles & Birds
Mammalia: Hair, Mammary Glands (milk), Endotherms, Heterodont Teeth, Diphyodont (2 sets teeth), Sebaceous/Sudoriferous Glands. Monotremes (egg-laying: platypus, echidna), Marsupials (pouch: kangaroos, opossums), Eutherians (Placentals): Complex placenta. Primates: Opposable thumbs, stereoscopic vision, large brain, nails (not claws). Prosimians vs. Anthropoids (monkeys, apes, humans).
Mammals

Practice quiz

  1. Which of the following is NOT a core principle of natural selection as proposed by Darwin and Wallace?

    • Organisms produce more offspring than can survive.
    • Individuals within a population exhibit heritable variations.
    • Traits acquired during an organism's lifetime are passed to its offspring.
    • Individuals with advantageous traits are more likely to survive and reproduce.

    Answer: Traits acquired during an organism's lifetime are passed to its offspring.

  2. A bat's wing and a human's arm share a similar bone structure, but serve different functions. This is an example of a(n) $___________$ structure, indicating $___________$ evolution.

    • analogous; convergent
    • homologous; divergent
    • vestigial; parallel
    • analogous; divergent

    Answer: homologous; divergent

  3. The Modern Synthesis integrates Darwinian natural selection with Mendelian genetics and population genetics. According to this synthesis, evolution is defined as a change in $___________$ over time within a population.

    • the number of species
    • allele frequencies
    • individual phenotypes
    • the geographic distribution of organisms

    Answer: allele frequencies

  4. Which of the following conditions, if violated, would lead to a population NOT being in Hardy-Weinberg equilibrium, and thus evolving?

    • Large population size
    • Random mating
    • Absence of natural selection
    • Presence of gene flow

    Answer: Presence of gene flow

  5. A small group of individuals from a larger population colonizes a new, isolated island. The genetic makeup of this new population is significantly different from the original population, primarily due to the limited number of founders. This scenario best describes which evolutionary mechanism?

    • Bottleneck effect
    • Gene flow
    • Founder effect
    • Directional selection

    Answer: Founder effect

  6. Two species of crickets look very similar but have different mating songs. Because their songs are distinct, they do not interbreed. This is an example of $___________$ reproductive isolation.

    • postzygotic; hybrid inviability
    • prezygotic; behavioral
    • postzygotic; hybrid sterility
    • prezygotic; temporal

    Answer: prezygotic; behavioral

  7. The streamlined body shapes of sharks (fish) and dolphins (mammals) are adaptations for efficient movement through water. Despite their distant evolutionary relationship, they have evolved similar forms. This is an example of:

    • Divergent evolution, leading to homologous structures.
    • Adaptive radiation, driven by sexual selection.
    • Convergent evolution, leading to analogous structures.
    • Coevolution, resulting from predator-prey interactions.

    Answer: Convergent evolution, leading to analogous structures.

  8. Which of the following provides the strongest evidence for the endosymbiotic theory, which explains the origin of mitochondria and chloroplasts?

    • They are roughly the same size as typical eukaryotic cells.
    • They contain their own circular DNA and ribosomes similar to bacteria.
    • They are capable of independent movement within the cell.
    • They are found in all eukaryotic organisms.

    Answer: They contain their own circular DNA and ribosomes similar to bacteria.

  9. Which of the following adaptations, crucial for larger plant size and efficient transport on land, is characteristic of seedless vascular plants but NOT found in nonvascular plants like mosses?

    • Alternation of generations
    • Cuticle
    • Vascular tissue
    • Spores for reproduction

    Answer: Vascular tissue

  10. All chordates, at some point in their life cycle, possess four key distinguishing features. Which of the following is NOT one of these features?

    • Notochord
    • Dorsal hollow nerve cord
    • Pharyngeal slits
    • A bony vertebral column

    Answer: A bony vertebral column

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