Test 8 (Ch. 22, 23)

• Systematics: Reconstruction and study of evolutionary relationships
• Phylogeny: Hypothesis about patterns of relationships among species
• Cladogram: Depicts a hypothesis of evolutionary relationships

  Clade: Species that share a common ancestor as indicated by the possession of shared derived characters
• Synapomorphy: derived character shared by clade members
• Taxonomy: The science of classifying living things
• Biological species concept (BSC)

  • Species = groups of interbreeding populations that are reproductively isolated
• Phylogenetic species concept (PSC)

  • Species = a population or set of populations characterized by one or more shared derived characters
• Taxons: (Least to Most Specific)

  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Types of

  Domain: Bacteria, Archaea, Eukarya(nucleus),

  Kingdom (in Eukarya): Protista, Plantae, Fungi, Animalia
• Bacteria

  • Most abundant organisms on Earth
  • Play critical roles throughout the biosphere
• Archaea

  • Typically live in extreme environments
  • Diverged early from bacteria
  • More closely related to eukaryotes than to bacteria
• Eukarya

  • compartmentalized cells
  • Appear in fossil record about 2.5 bya
  • Their structure and function allowed multicellular life to evolve
  • The roots of the eukaryotic tree remain elusive
• Prokaryotes

  • Smallest and simplest, and most abundant forms of life
  • Likely originated on earth over 3.5 billion years ago
  • Fall into 2 domains

  1. Bacteria
  2. Archaea
• Prokaryotic Cell Structure

  3 basic shapes

  1. Bacillus – Rod-shaped (tube/pill like)
  2. Coccus – Spherical (Grape/circle like)
  3. Spirillum – Helical-shaped (squiggle snake)

  Cell Wall - Peptidoglycan forms a rigid network (which maintains the shapes)
• Gram positive bacteria

  • Thick, complex network of peptidoglycan
  • Also contains lipoteichoic and teichoic acid
  • Looks Purple

  Gram negative bacteria

  • Thin layer of peptidoglycan
  • Second outer membrane with lipopolysaccharide
  • Resistant to many antibiotics
  • Looks Pink
• How Bacteria move: Flagella

  • Slender, rigid, helical structures
  • Composed of the protein flagellin
  • Involved in locomotion – spins like propeller

  How Bacteria Attach: Pili

  • Short, hairlike structures
  • Found in gram-negative bacteria
  • Aid in attachment and conjugation
• How Bacteria survive Harsh environments: Endospores

  • Develop a thick wall around their genome and a small portion of the cytoplasm
  • Form when exposed to environmental stress
  • Highly resistant to environmental stress, especially heat
  • When conditions improve can germinate and return to normal cell division
• Prokaryotic Genetics

  • Prokaryotes do not reproduce sexually
  • 3 types of horizontal gene transfer

  1. Conjugation – cell-to-cell contact
  2. Transduction – by bacteriophages
  3. Transformation – from the environment

  All 3 processes also observed in archaea
• Antibiotic Resistance

  • R (resistance) plasmids
  • Encode antibiotic resistance genes
  • Acquire genes through transposable elements
  • Important factor in appearance of antibiotic resistant strains of Staphylococcus aureus
• Prokaryotic Metabolism

  • Acquisition of Carbon
  • Autotrophs – from inorganic CO2
  • Photoautotrophs – energy from Sun**
  • Chemolithoautotrophs – energy from oxidizing inorganic substances
  • Heterotrophs – from organic molecules
• Influenza

  • One of the most lethal viruses in human history
• Caused by Bacteria:

  • Tuberculosis (TB)
  • Peptic ulcers
  • Dental caries (tooth decay)
• Viruses:

  Not organisms

  All viruses have same basic structure

  • Nucleic acid core surrounded by capsid
  • No cytoplasm – not a cell

  Nucleic acid can be DNA or RNA

  • Circular or linear
  • Single- or double-stranded
• Viral Shapes:

  • Most viruses come in two simple shapes

  1. Helical – rod/thread like
  2. Icosahedral – soccer ball/dice shape

  • Some viruses are complex
  • T-even bacteriophages
  • Enveloped viruses are polymorphic
• Bacteriophage: viruses that infect bacteria
• Conditions for Pandemics

  1. new strain must contain a novel combination of H and N spikes
  2. the new strain must be able to replicate in humans and cause death
  3. the new strain must be efficiently transmitted between humans.