UNIT 4

• Niche

  The range of resources that a species uses and the abiotic conditions it can tolerate
• Fundamental niche

  The entire set of conditions
• Realized niche

  The set of conditions actually used
• Realized niche

  Smaller than fundamental niche
• Trophic levels

  • Primary producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
• Dominant/foundation species

  Have large effects by virtue of their considerable abundance
• Keystone species

  Have effects that are large in proportion to their abundance (usually a trophic interaction)
• Biodiversity

  • Genetic diversity
  • Taxonomic diversity
• Richness

  The number of species
• Abiotic hypotheses for biodiversity

  • Spatial: the larger the area, the more space and potential geographic diversity
  • Energy: a larger amount of energy and nutrients in the form of biomass can support many organisms in a community
• Biotic hypotheses for biodiversity

  • Ecological interactions: a higher complexity of species interactions leads to higher rates of niche differentiation
  • Evolutionary history: a higher species diversity is a product of relatively high speciation rates, low extinction rates, high immigration rates (colonization), and/or low emigration rates
• Biodiversity

  • Decreases with latitude
  • Increases with area
• Equilibrium: the higher the population, the higher the probability of extinction
• Island size: larger islands have more colonists and a lower rate of extinction = greater biodiversity
• Evenness

  How evenly are the species distributed
• Species composition

  The species identity
• Ecosystem diversity

  The range of communities and the abiotic environment
• Bottom-up trophic control mechanisms

  • Resources
  • Nutrients
  • Water
  • Sunlight
• Top-down trophic control mechanisms

  • Consumption
  • Predation
  • Herbivory
  • Parasites
  • Viruses/diseases
• Trophic cascade

  Disruption of a food web by loss or reduction in abundance by one or more of its members
• Peduzzi et al paper

  1. Objective: to find the cause of flamingo population fluctuations

  2. Hypothesis: viruses can cause a bottom-up cascade

  3. Trophic cascade: cyanophage virus, cyanobacterium, flamingo
• Taxonomics

  The study of naming, describing, and classifying organisms
• Systematics

  The study of the pattern of relationships among taxa - the organization of life
• Phylogeny

  A hypothesis of how taxa are evolutionarily related to each other
• Node

  Where branches split - common ancestor
• Monophyletic

  Share an ancestor (clade)
• Polyphyletic

  Shares similar traits but does not include the most recent common ancestor (not a clade)
• Paraphyletic

  Includes an ancestor and some descendants, but not all (not a clade)
• Parsimony

  The arrangement of taxa that requires the fewest changes and is the most likely
• Synapomorphy

  Traits shared by two or more taxa
• Homologous traits

  Similar origin
• Analogous traits

  Similar function
• Divergence

  Related species evolve different traits (environmental selection)
• Convergence

  Unrelated but share similar traits
• Organ paper

  1. Objective: used the gene size of current bird species to make inferences about extinct dinosaurs

  2. Conclusion: the genome size observed in modern birds likely originated from non-avian dinosaurs
• Similarities between bacteria and archaea

  • Prokaryotes
  • No membrane around DNA
  • Single circular chromosomes
  • No energy-producing organelles
  • Very few cell compartments
  • Asexual reproduction
• Differences between bacteria and archaea

  • Bacteria have peptidoglycan in the cell wall
  • Archaea cell membrane is unique phospholipids made from isoprene
  • Bacteria transcription is different than Eukarya and Archaea
  • Antibiotics that are effective on Bacteria don't work on Archaea
• Value of studying bacteria and archaea

  • Lots of uncatalogued diversity (genetic/taxonomic)
  • Can live in extreme environments
  • Helps to develop medicines
  • Can be used to clean pollution
  • Metabolic diversity
• Metabolic types of bacteria and archaea

  • Photoautotrophs: energy from sunlight, carbon from CO2
  • Chemoautotrophs: energy from environment, carbon from CO2
  • Photoheterotrophs: energy from sunlight, carbon from environment
  • Chemoheterotrophs: energy from environment, carbon from environment
• Mechanisms to increase variation in bacteria and archaea

  • Horizontal gene transfer
  • Conjugation
  • Transduction
  • Transformation