Bio 2 Exam 1

• • Life: an organized genetic unit capable of metabolism, reproduction, and evolution. A sustained chemical system capable of undergoing Darwinism evolution. DNA, cells, metabolism, adaptation, homeostasis, growth, reproduction, evolution. ALL HAVE METABOLISM IN COMMON!!!!!!
• Metabolism is the absorption of nutrients, excretion of wastes, energy acquisition and transformation (ex. Krebs Cycle), and cellular synthesis.
• Reproduction is growth (duplication of all cellular components) and division of discrete units (cells).
• Evolution is variation, reproduction, and mutation (mistakes in copying cell components)
• Origins of life 1.

  Organic molecules like nucleotides and amino acids produced prior to the existence of cells.
• Origins of life 2.

  Nucleotides and amino acids became polymerized to form DNA, RNA, and proteins.
• Origins of Life 3.

  Polymers became enclosed in membranes
• Origins of life 4.

  Polymers enclosed in membranes acquired cellular properties
• Origins of Life 1. Origin of organic molecules

  Conditions on Earth were more conducive to SPONTANEOUS formation of organic molecules. This formation is known as the prebiotic (primordial) soup.
• Origins of Life 1. Origin of organic molecules

  • reducing atmosphere hypothesis - atmospheric reactions with lightening, solar, and cosmic radiation.
  • extraterrestrial hypothesis - on meteorites molecules formed in interstellar clouds
  • deep sea vent hypothesis - underwater reactions with volcanic vents
• Reducing Atmosphere Hypothesis

  • Miller-Urey 1952's Experiment: set up sterile anaerobic atmospheric conditions with electrical discharge. Resulted in SPONTANEOUS FORMATION of simple organic molecules (monomers) which gave way to amino acids, simple carbohydrates, and simple lipids.
• Origins of life Stage 2. Organic Polymers

  • experimentally, prebiotic synthesis of polymers WAS THOUGHT IMPOSSIBLE in aqueous solutions (since hydrolysis competes with polymerization). However, experiments have shown formation of nucleic acid polymers and polypeptides on CLAY SURFACES
• Origins of life Stage 3. Formation of Boundaries

  • Formation of a boundary that SEPARATED THE INTERNAL POLYMERS from the environment.
  • Protobiont (also called protocells) aggregate of molecules and macromolecules that acquired a BOUNDARY. Such as a LIPID BILAYER, that allowed it to maintain an INTERNAL CHEMICAL ENVIRONMENT distinct from that of its surroundings.
• What are characteristics that make protobionts possible precursors to living cells?

  1. a BOUNDARY separated external environment from internal contents.
  2. polymers inside the protobiont contained INFORMATION
  3. polymers inside the protobiont had ENZYMATIC FUNCTION
  4. protobionts capable of SELF REPLICATION
• Origins of life 3. Formation of boundaries 


  Living cells may have evolved from coacervates and liposomes.
• Origins of life 4. RNA world

  • Majority of scientists favor RNA as the FIRST MACROMOLECULE of protobionts
  • RNA has three key functions: ability to store information, capacity for self replication, and enzymatic function (ribozymes)
• Origins of life 4. RNA world

  Advantages of DNA/RNA/protein world include:

  • INFORMATION STORAGE: DNA would have relieved RNA of informational role and allowed RNA to do other functions, DNA is less likely to suffer mutations.
  • METABOLISM AND OTHER CELLULAR FUNCTIONS: proteins have a greater catalytic potential and efficiency, and can perform other tasks (cytoskeleton, transport, etc.)
• Fossils: layers of SEDIMENTARY rock containing fossils. Over time sediments pile up and become rock.
• Radioisotope Dating

  • half-life is the length of time required for exactly one-half of original isotope to decay.
• Changes in living organisms are the result of genetic changes and environmental changes. They can allow for new types of organisms and are responsible for many extinctions.
• Major environmental changes include climate/temp, atmosphere, land masses, floods, glaciations, volcanic eruptions, and meteoric impacts.
• Archaean (3.8 to 2.5 bya)

  • first cells were PROKARYOTIC (LACK NUCLEI)
  • all life was prokaryotic during archaean eon
  • almost no free oxygen so organisms were ANAEROBIC (NOT REQUIRE OXYGEN)
  • AUTOTROPHS (ENERGY VIA PRODUCTION) evolved as supply of organic molecules dwindled
• Evidence of life Archaean Eon

  AUTOTROPHIC cyanobacteria were preserved but HETEROTROPHIC ancestors were not.

  • formed STROMATOLITES (microbial mats of layered structure of calcium carbonate)
• Proterozoic (2.5 bya - 543 mya)

  • multicellular EUKARYOTES (CELLS WITH NUCLEUS) arise (1.5 bya)
  • two possible origins: individuals form a colony and single cells divide but stay stuck together. Consequence = allowed for complexity and specialization of cells
  • ex. volvocine green algae display variations in the degree of MULTICELLULARITY.
  • MILESTONE IN LIFE = eukaryotes include all multicellular organisms
  • First animals were invertebrates
  • BILATERAL SYMMETRY - facilitates locomotion
• Proterozoic Eon - Origin of Eukaryotic Cells

  Modern eukaryotes -> DNA found in nucleus, mitochondria, and chloroplasts -> both ARCHEA and BACTERIA contributed substantially to NUCLEAR GENOME -> ENDOSYMBIOTIC RELATIONSHIPS gave rise to eukaryotic cells
• Phanerozoic Eon = diversification of invertebrates and colonization of land plants and animals
• Cambrian (543-490 mya)

  • warm and wet with no ice at poles
  • CAMBRIAN EXPLOSION: abrupt increase in diversity of animal species (case unknown -> shell evolution, atmospheric oxygen, "arms race"
  • all existing major types of marine invertebrates plus many others that no longer exist.
• Ordovician (490-443 mya)

  • diverse group of marine invertebrates including trilobites and brachiopods
  • PRIMITIVE LAND PLANTS AND ARTHROPODS FIRST INVADE LAND
  • towards end, abrupt climate change (large glaciers) resulting in MASS EXTINCTION (over 60% of marine invertebrates go extinct)
• Silurian (443-417 mya)

  • coral reefs appeared
  • large colonization by terrestrial plants and animals
  • spiders and centipedes
  • earliest VASCULAR PLANTS (transport system for water and nutrients)
• Devonian, Age of Fish (417-354 mya)

  • ferns, horsetails and seed plants (GYMNOSPERMS), insects emerge
  • TETRAPODS -> amphibians emerge
  • near end, prolonged series of EXTINCTIONS eliminate many marine species
• Carboniferous (354-290 mya)

  • rich COAL DEPOSITS formed
  • very large plants, trees, amphibians prevalent
  • first flying insects
  • AMNIOTIC EGG EMERGES -> EGG PROTECTED BT MEMBRANE
• Permian (290-248 mya)

  • PANGAEA (FORMED VIA CONTINENTAL DRIFT)
  • amphibians prevalent but reptiles became dominant
  • first MAMMAL-LIKE REPTILES appeared
  • at the end, largest known mass EXTINCTION EVENT (KNOWN AS THE GREAT DYING OR PERMIAN-TRIASSIC EXTINCTION) -> 90-95% of all marine species and large proportion of terrestrial species eliminated. Caused by glaciations and/or volcanic eruptions
• Triassic, Age of Dinosaurs (248-206 mya)

  • reptiles plentiful
  • first DINOSAURS and first true mammals
  • gymnosperms dominant land plant
  • volcanic eruptions led to global warming and mass extinctions near the end
• Jurassic (206-144 mya)

  • gymnosperms still dominant
  • dinosaurs dominant land animals
  • first known bird
  • mammals present but not prevalent
• Cretaceous (144-65 mya)

  • dinosaurs still dominant on land
  • earliest flowering plants, ANGIOSPERMS
  • another MASS EXTINCTION at the end of the period (cretaceous-tertiary or K-T extinction) -> dinosaurs extinct but archosaurs survived (crocadilians and birds)
• K-T Extinction (~66 million years ago)

  • large meteorite hit region known as the Yucatan, lifting massive amounts of debris -> clouding the atmosphere resulting in an "impact winter" lasting ~2 years -> climate change cascade lasted ~10,000 years
• Tertiary, Age of Mammals (65-1.8 mya)

  • mammals that survived diversified rapidly
  • ANGIOSPERMS (flowering plants) become the dominant land plant
  • whales appeared
  • HOMINOIDS APPEARED ABOUT 7 MYA
• Quaternary (1.8 mya to present)

  • PERIODIC ICE AGES cover much of Europe and North America
  • certain hominids become more human-like
  • HOMOSAPIENS APPEAR
• Geological Time Scale

  • Archaean = bacteria and archaea
  • Proterozoic = eukaryotes
  • Phanerozoic: - paleozoic = land colonized - mesozoic = dinosaurs - cenozoic = hominoids
• Evolution: HERITABLE CHANGE in one or more characteristics of A POPULATION from ONE GENERATION TO THE NEXT