GGR Week 3

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  1. Who was Terry Erwin, and what was his experiment with tree beetles?
    Fogged some trees in an area and put sheets in the ground to collect tree beetles. He used this number to extrapolate how many species he thinks live on earth.
  2. Explain the latitudinal gradient as it relates to biodiversity.
    We can see a pattern of species which are found around the world to have richer distributions the closer to the equator than away. It looks like a normal distribution turned horizontal.
  3. Why are there more species close to the equator?
    More food available?
    If there are more plants and primary producers, it allows for more secondary consumers. But how did the primary consumers get there in the first place?
  4. Why are there more species close to the equator?
    More land present?
    There is more land on the equator, so there is more room to roam and co-habitate. However, boreal forests exist in the equator and do not have representative species richness.
  5. Why are there more species close to the equator?
    Stable climate hypothesis.
    Because the equator has never been subject to crazy ice ages or things like that, it has allowed species richness to increase unabated.
  6. Why are there more species close to the equator?
    Changing climate hypothesis.
    While the equator has not been subject to massive earrth-changing events, climate fluctuations are plenty, and could cause enough of a reason for new species to emerge.
  7. Why are there more species close to the equator?
    Energy Hypothesis.
    There is ample water and sunlight in the equator, which allows primary producers to thrive. In turn this allows for more secondary consumers to thrive as well. Furthermore, a lot of species near the equator have fast metabolisms and reproduce much faster. Natural selection happens at an increased rate here, and this increases species richness.
  8. What is succession?
    The change from one set of species to another over a span of time.
  9. What is primary succession, and give an example.
    • 1st colonization of previously lifeless surface.
    • Example is the island off Iceland where a volcano created a new island.
  10. What is secondary succession, and give an example.
    • Colonization and change after a disturbance.
    • Say a forest fire comes through. First we would expect to see 
    • Annuals (1 year)
    • Perennials (10 years)
    • Shrubs(40 years)
    • Young Forest (100 years)
    • Mature Forest (>100 years)
  11. What characteristics do Early Successional (Pioneer) species have?
    • Many small, wind-dispersed seeds.
    • Ability to handle variety of climate conditions (harsh winds, etc...)
  12. What characteristics do mid/late successional species have?
    • Longer life span.
    • Shade tolerant.
    • Larger non wind-borne seeds.
  13. What is traditional (Clementian) succession, and what are some problems with it?
    • A sequence (sere) of plant communities (seral stages) characterized by increasing complexity of the lifeforms, with the end stage being the climax vegetation. Works through facilitation.
    • However, this ignores impact of herbivores, disturbance, and the seral stages are not well-defined. Also, most land is undergoing secondary succession (modified seed bank).
  14. Name and describe the 3 alternative succession models.
    • Tolerance Model - Fastest growing dominate in short term, slower growers eventually out compete
    • Inhibition Model - Early colonizers ensure other species cannot establish themselves
    • Random - No facilitation or inhibition occurs
  15. What is cosmopolitan distribution, and give an example.
    A species that is widely distributed around the world. An example is bats (chiroptera)
  16. What is an endemic species? Name the two type of endemic species and describe them.
    • Endemic: found only in one restricted area and no where else
    • Paleoendemic: old endemic that once had a larger distribution
    • Neoendemic: evolved through isolation, not yet had time to spread out
  17. What is a disjunct distribution? Describe the two types, and give examples.
    • Disjunct - Taxa found in two or more areas that are widely separated
    • Evolutionary relics: once had very broad distribution but no longer (Magnilia grandiflora)
    • Climactic relics: widely distributed, but now only located in a few “islands” which remained climatically favourable (Tetracanthella arctica)
  18. What must happen for a species to increase its distribution?
    • Travel to new area
    • Withstand (unfavourable) conditions along the way
    • Establish viable population upon arrival
  19. Name and describe the 3 ways in which species can increase their distribution.
    • Jump dispersal: long distance movement by individuals
    • Diffusion: gradual spreading at margins of geographic distribution
    • Secular migration: hundred of generation, with species evolving along route
  20. Name and describe the 3 types of routes that facilitate dispersal.
    • Corridors: Routes that allow most taxa to move from one region to another. Does not discriminate.
    • Filter: More restrictive than corridor, with select subset of species able to pass through
    • Sweepstakes Routes: Chance dispersal by individuals.
    • Colonization by individuals.
    • Colonization of isolated islands by flying or floating
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GGR Week 3
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