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Chapter 24-25 - Coggle Diagram

- - - - Abiotic Synthesis of Small Organic Molecules Building blocks: amino acids, nitrogenous bases, simple sugars, lipids.
        
        Oparin–Haldane hypothesis (1920s): early atmosphere = reducing “primordial soup.”
        
        Miller–Urey experiment (1953): simulated early atmosphere = amino acids & organics.
        
        Volcanic conditions (re-analyzed in 2008): produced even more amino acids
        
        Hydrothermal vents
        
        Meteorites (Murchison, 1969)
    - - Purine bases (adenine, guanine) formed spontaneously
      - Pyrimidines (cytosine, uracil) formed (2009).
      - Polymers from monomers: amino acids or nucleotides polymerize on hot sand, clay, or rock.
      - Polymers = crude catalysts
    - - Droplets with membranes, maintain internal chemistry.
      - Evidence
        
        Vesicles form spontaneously from lipids
        
        Montmorillonite clay speeds up vesicle formation.
    - - RNA world hypothesis
        
        RNA = first genetic material.
        
        Ribozymes → RNA molecules act as catalysts + self-replicators.
        
        RNA folds into 3D shapes → some sequences replicate faster + more accurately → natural selection at molecular level.
      - Transition to DNA:
        
        Transition to DNA:
        
        DNA = more stable & accurate.
        
        Allowed larger genomes, more complex inheritance → modern life forms.
  - - - Richest in sedimentary strata also found as:
        
        Mineralized remains (petrified wood, permineralized bone)
        
        Trace fossils (footprints, burrows)
        
        Amber inclusions
        
        Frozen/bog-preserved bodies
      - Reading time in rocks
        
        Relative age: position in strata (older below, younger above).
        
        Absolute age → radiometric dating
        
        Carbon-14
        
        Potassium-Argon
        
        Sedimentary fossils are often bracket-dated
    - - Jaw bones: non-mammalian tetrapods have multiple bones in lower jaw mammals have one (dentary)
      - Middle ear: the articular & quadrate migrate to the ear to become malleus & incus (mammals have three middle-ear bones others have one).
      - Teeth: from single-pointed to differentiated (incisors, canines, premolars/molars).
      - Temporal fenestra position/size and muscle attachment change, improving bite power/precision.
      - Pattern can be punctuated or gradual in different lineages, but across many fossils the transition is stepwise and continuous.
  - - - Earth forms: ~4.6 Ga (billion years ago)
      - Oldest life (prokaryotes; stromatolites): ~3.5 Ga
      - Oxygen revolution (O₂ rise): begins ~2.7 Ga atmosphere spikes ~2.4 Ga
      - First eukaryotes: ~1.8–2.1 Ga (endosymbiosis leads to mitochondria first; plastids later)
      - Multicellular eukaryotes: ~1.2–1.6 Ga (early red algae fossils
      - Ediacaran biota (large soft-bodied euks): 635–541 Ma (million years ago)
      - Cambrian explosion (many animal phyla appear in fossils): ~535–525 Ma
      - Land colonization:
        
        Plants–fungi symbioses/mycorrhizae evident by ~400 Ma
        
        Early land plants: ~470 Ma vascular plants soon after trees by ~385 Ma
        
        Arthropods on land: ~450 Ma
        
        Tetrapods (from lobe-finned fishes): ~365 Ma
    - - Prokaryotes dominated the oceans for ~2 billion years.
        Stromatolites (layered microbial mats) are key fossils (~3.5 Ga).
    - - Cyanobacteria evolve oxygenic photosynthesis
      - O₂ rise is toxic to many anaerobes
    - - Serial endosymbiosis
      - Evidence: bacterial-like inner membranes
    - - After eukaryotes arise, unicellular diversity flourishes
      - diacaran biota large, mostly soft-bodied eukaryotes
    - - many animal phyla show up in fossils; predators and defensive structures
      - Molecular clocks indicate many phyla originated earlier
  - - - Plate tectonics & continental drift
        
        Habitat change/loss: Pangaea assembly reduced shallow seas, altered climates.
        
        Allopatric speciation at scale: breakup of supercontinents isolates biotas (Australia’s marsupial radiation vs. eutherians elsewhere).
        
        Climate forcing: latitude shifts; uplift (Himalayas) alters circulation; organisms must adapt, move, or go extinct.
        
        Explains odd fossil distributions (same freshwater reptile on now-distant coasts).
      - Mass extinctions (5)
        
        Permian (≈252 Ma): largest; ~marine life devastated; many insect orders lost.
        
        Cretaceous–Paleogene
      - Adaptive radiations
        
        Definition: rapid speciation producing many species that occupy different niches.
        
        When they happen:
        
        Following key innovations ( seeds armor).
        
        Upon colonizing new regions with little competition ( Hawaii).
  - - - Heterochrony = evolutionary shifts in the rate/timing of developmental events = big adult-form differences.
        
        Human vs chimp skulls slowed jaw growth in humans = adult skull more “infant-like”
        
        Bat wings: increased growth of finger bones.
        
        Whales: slowed growth of hindlimb/pelvis → limb reduction.
      - Pedomorphosis: reproductive maturity arrives early relative to somatic development = adults retain juvenile traits
    - - Controlled by homeotic genes (master regulators).
        
        Hox genes (animals): positional info along body axis; shifting Hox expression domains or function can repattern segments/appendages
        
        MADS-box (plants): control floral organ identity expression changes yield different flower forms.
    - - Sequence changes alter protein function everywhere it’s expressed
      - Regulatory changes (enhancers/switches) tweak where/when/how much a gene is transcribed
- - - - species
        
        Can interbreed in nature
        
        Produce viable, fertile offspring
        
        Do not successfully breed with other groups
        
        Humans worldwide can interbreed
      - Limitations- Not useful for fossils and doesn’t apply to asexual species
      - Alternative Species Concepts
        
        Morphological species concept
        
        Based on body shape/structural features
        
        Ecological species concept
        
        Based on ecological niche
    - - Prezygotic barriers
        
        Temporal isolation - different breeding seasons
        
        Behavioral isolation - unique courtship rituals)
        
        Mechanical isolation - incompatible anatomy
        
        Gametic isolation -sperm can’t fertilize eggs
        
        Habitat isolation - different habitats
      - Postzygotic
        
        Reduced hybrid viability- frail offspring
        
        Reduced hybrid fertility - sterile hybrids
        
        Hybrid breakdown -F1 fertile, F2 sterile/weak
  - - - Allopatric (“other country”): geographic barrier
        
        How it starts: physical barrier (lake level drops, river course changes, colonization of remote area)
        
        After isolation: separate gene pools - mutation, natural selection, drift, sexual selection- divergence
        
        Reproductive isolation often evolves as a by product ( mate choice, morphology, timing)
      - Sympatric (“same country”): no geographic barrie
        
        Polyploidy
        
        Autopolyploidy: chromosome doubling within one species
        
        Allopolyploidy: hybridization between species
        
        Sexual selection
        
        Lake Victoria cichlids females choose by male color
        
        Habitat differentiation
  - - - Often narrow bands where habitats meet (ecotones) or patchy mosaics (spotty across landscape).
      - No strong geographic barrier needed
      - Shifts in habitat/climate can move zones or create new ones.
      - Reinforcement (stronger barriers)
        
        If hybrids are less fit, selection favors prezygotic isolation (assortative mating).
        
        Prediction: Barriers stronger in sympatry than allopatry.
      - Fusion (collapse into one species)
        
        If barriers are weak and gene flow is high
      - Stability
        
        Hybrids persist because they’re favored in some microhabitats/years or because continuous parental migration keeps making hybrids
  - - - Fossil patterns
        
        Punctuated equilibria
        
        Gradual change
      - What the tempo means
        
        “Sudden” in fossils can still be ≤ 100k windows.
        Average interval between speciation events
    - - Speciation begins when gene flow is cut
    - - Few genes (sometimes one) can suffice
        
        Euhadra snails- single gene → shell coiling direction → mechanical isolation.
      - Many genes / interactions
        
        Sunflower hybrid zones: multiple chromosome segments underlie postzygotic barriers.