Classification, Viruses, & Bacteria - Study Notes

CLASSIFYING LIVING THINGS

• Binomial Nomenclature:
  • Two-part scientific name: Genus (Capital) + species (lowercase), italicized or underlined.
  • Example: Homo sapiens
• Dichotomous Key:
  • A tool for identifying organisms using paired statements.
  • Follow each step carefully to narrow down options.

VIRUSES

• Viruses are non-living particles made of DNA/RNA and a protein coat (capsid).
• They need a host cell to reproduce.
• Lytic Cycle:
  1. Attachment
  2. Entry
  3. Replication
  4. Assembly
  5. Lysis (cell bursts)
• Lysogenic Cycle:
  1. Attachment
  2. Entry
  3. DNA joins host DNA (provirus)
  4. Host replicates virus DNA
  5. Can switch to lytic cycle later
• Host: The organism a virus infects.
• Vector: Carrier of a virus (e.g., mosquito).
• RNA vs DNA Virus:
  • RNA: Mutates more easily (flu, HIV, COVID-19).
  • DNA: Stable replication (herpes, smallpox).
• Vaccines:
  • Contains weak/inactive virus.
  • Helps body create antibodies.
  • Immune memory defends against future infections.
• Transmission & Prevention:
  • Spread: cough, touch, fluids, air.
  • Prevent: isolate, wash hands, wear mask.

BACTERIA

• Not all are harmful; many are beneficial (digestion, food production, decomposing).
• Prokaryotic vs Eukaryotic Cells:
  • Prokaryotic (bacteria):
    • No nucleus
    • Small
    • No membrane-bound organelles
  • Eukaryotic:
    • Has nucleus
    • Larger
    • Complex organelles
• Viruses are smaller than bacteria.
• Archaebacteria vs Eubacteria:
  • Archaebacteria: extreme environments
  • Eubacteria: everywhere else
• Bacterial Shapes:
  • Coccus (round)
  • Bacillus (rod)
  • Spirillum (spiral)
• Killing Bacteria:
  • Antibiotics (attack cell walls or proteins)
  • Heat, disinfectants
• Antibiotics:
  • Medicines that kill or inhibit bacteria (not viruses).
• Culturing Bacteria:
  • Use agar plates
  • Sterile tools
  • Right temp (37°C)
  • Moisture and oxygen depending on species