BIOL 201 - lectures 1 and 2

Card Set Information

BIOL 201 - lectures 1 and 2
2011-09-21 09:16:52

lecture 1 and 2
Show Answers:

  1. changes in the tree of life concept
    • Universal phylogenetic tree based on nucleotide changes within the rRNAsequence present in the small subunit of ribosomes
    • Aristotle’s ‘ladder of life’
    • Whittaker’s ‘five kingdoms’based on morphology
    • Woese’s ‘universal tree of life’ based on rRNAsequences (1990-)
  2. Why is an understanding of the diversity of life important?
    • A sense of ‘our place in the scheme of things’…“Where do we come from? What are we? Where are we going?”
    • The wonder of our natural environment
    • Human subsistence – e.g. crop production
    • Human health
    • Management of our environment – e.g. ecology, conservation, species invasions, pollution…
  3. What would we like you to be able to do by the end of this course?
    • Primary:
    • – Genetic mutation
    • – Environmental heterogeneity and change (e.g. climate, plate tectonics)
    • Secondary:
    • – Development of more complex structures within organisms (e.g. nuclear membrane, multicellularity, vascular system)
    • – Colonisation of novel habitats (e.g. land surfaces)
    • – Organism effects on environment (e.g. O2in the atmosphere)
    • – Interactions among organisms (e.g. symbioses, pathogenesis, competition for limiting resources)
    • – Development of more complex reproductive systems (e.g. diploidy, alternation of generations, sexual reproduction)
  4. What are the characteristics of living organisms?
    • Microspheres: simple aggregations of proteins; grow; bud-off; could form sheets (membranes) that enclose organic-rich media
    • Organisms can: 1) Grow (and survive?)2) Reproduce3) Pass on characteristics to next generation (heredity)
    • All organisms achieve these traits through:
    • • Organization based on cells bounded by semi-permeable membranes
    • • ATP-based energy currency
    • • Chemical machinery for the synthesis and degradation of essential molecules
    • • Heredity via nucleic acids
  5. Early life
    • Millar’s expt suggestingpotential for amino acid, sugar and nucleic acid generation on early earth
    • Primitive heterotrophs began to compete for limited resources
    • Autotrophs (Gk auto “self” and trophos “feeder”) Evolved after heterotrophs Photosynthesis:
    • •requires specialized pigments
    • •changed the Earth’s atmosphere (ozone, O2)
    • •influenced the evolution of life
  6. Lecture 2 Start
  7. Differing concepts of ‘Species’
    • Biological species – Reproductive isolation: A group of natural populations whose members can interbreed with one another but cannot interbreed with other such groups
    • Morphological species – identified based on differences in shape or structure
    • Genetic species – identified based on differences in nucleic acid sequence
    • Prokaryotic ‘species’??– Strains that share a common set of stable properties
  8. Systematics – the study of biological diversity
    • Taxonomics – theory and practice of classifying organisms
    • A stable system for naming and identifying organisms
    • – Framework for classifying ancestral relationships
    • – Assessment and management of biodiversity
    • Phylogenetics – theory and practice of discovering the evolutionary interrelationships among organisms.
    • Ultimate goal is to discover the evolutionary relationships between all the branches of the tree of life
  9. The Father of Taxonomy: Carl Linnaeus (1707 – 1778)
    • 1753 – ‘Species Plantarum’ (“The Kinds of Plants”)
    • Polynomial – up to 12 words– e.g. Catnip: Nepeta floribus interruptespicatus pedunculatis
    • Binomial – 2 word shorthand version
    • (kpcofgs)
  10. Virus
    • = a genome that replicates itself within a host cell by directing the machinery of the host cell to synthesize viral nucleic acids and proteins
    • Are viruses organisms?
    • 1) Lack fundamental cellular features – e.g. plasma membranes, cytoplasm, ribosomes, or any enzymes for protein synthesis or energy production
    • 2) Do not grow by increasing in size or dividing
    • 3) Do not respond to external stimulii
    • 4) Cannot carry on independent metabolism
    • Viruses infect almost every kind of organism.
    • Human viruses: influenza, chicken pox, hepatitis, AIDS, West Nile, SARS, Avian flu, Ebola
    • Many viruses of other animals. E.g. rabies, mad cow disease
    • Plant viruses > 2000 known. E.g. tobacco mosaic viru
  11. Origin of Viruses
    • No fossil record
    • • Renegade segments of host genomic material that became partially independent– “Infectious nucleic acids”– Replicate independently in another cell– Acquired protein to protect nucleic acid
    • • Extremely rapid evolution
    • • Have evolved independently many times
  12. Viral Structure
    • Very small (~1/100ththe size of a bacterium)
    • • DNA (mainly animal viruses) or RNA (mainly plant viruses) single or double stranded and surrounded by protein coating
    • • Identifying the protein is often the key to medical treatment
    • • Some have an outer lipid envelope
    • • Protein coating – helical; spherical; sometimes with a tail
    • Viruses vary greatly in size and morphology
  13. Viral Transmission
    • Bodily fluids (e.g. herpes virus)
    • Animal vectors (e.g. Human Avian influenza H5N1)
    • Air
    • Hand contact
  14. Development of virus treatment strategies
    • Vaccus (latin for cow)
    • • Smallpox often fatal (10-40% of victims died); survivors disfigured and blinded
    • • Local English peasants noticed that those who had contracted cowpox were immune to smallpox
    • • Edward Jenner in 1796 extracted contents of a pustule from the arm of a milkmaid with cowpox symptoms, and injected it into a young boy.
    • • Boy experienced mild symptoms
    • • Jenner then inoculated the boy with smallpox…the boy did not develop any symptoms
    • • ….smallpox eradication one of the greatest public health achievements ever
    • Vaccine: a preparation of a weakened pathogen or some of its components that primes the organism’s defense mechanisms against the virulent strain.
    • • Antiviral drugs: Inhibit reverse transcriptase as it attempts to synthesise DNA from the original viral RNA (e.g. AZT vs. AIDS); Protease inhibitors that block virion protein capsule assembly
  15. Diversity within the Influenza virus
    • Influenza A, B and C groups (linear RNA).
    • • A (most common) has subtypes based on antigens of the hemaglutinin (H) and neuraminidase (N) proteins on the outer envelope…H2N1 …H10N7…etc.
    • Virus-contaminated secretions enter respiratory system as aerosols or via ingestion.
    • Neuraminidase hydrolyses epithelial mucus, and then hemaglutinin tail attaches to host blood cells to begin infection.
    • Infect most animals especially chickens – major reservoir for human infection is from chickens via pigs.
  16. Antigenic drift
    • Small mutations in the RNAbased sequences for the H and N proteins in a single strain occur each year. Variation largest in Infl. A and moderate in Infl. B.
    • Flu jab is a vaccine developed each year based on epidemiological predictions of the specific antigen structures of the prevalent Influenza A virus strains.
  17. Antigenic shift
    • Major genetic reassortment when two strains (from humans and/or other animals) infect the same cell and become incorporated into a single new capsid…leading to novel genome and H N combination
    • • A major societal health concern (epidemic risk) E.g. Spanish flu (H1N1) of 1918 killed 40 million peopl