Summary: Ecology

Read the summary and the most important questions on Ecology

• Ecology

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• Four Aspects of a Species' Life History

  1. Metamorphosis
  

  • Organisms undergo radical changes in morphology, physiology, and ecology over the course of their life cycle.

  
  2. Diapause
  

  • Presence of a resting stage somewhere in life cycle

  
  3. Senescence 
  

  • Process and timing of aging and death of an organism and why

  
  4. Reproductive Patterns
  

  • Magnitude and time of reproductive events

• Metamorphosis Ecological Advantages

  1. Reduces Competition (w/n species)
  

  • Different niches
  • Higher # in given habitat

  
  2. Easy to exploit predictably variable habitats (predictable transient life cycle)
  

  • Compartmentalize Life Stages (can predict when habitat/resources w/n the habitat will disappear)
  • Young: feeding & growth
  • Adult: dispersal & repro.

  
  
  

  • Use transient resources
  • Body plan changes to match other needs in the life cycle

• Strategies in harsh Unpredictable environments

  1. Resistant stages at set time intervals (doesn't really take environmental cues but time intervals "like ticking of a clock")
  

  • Ex. Freshwater sponges

  
  2. Multiple young in different developmental stage simultaneously
  

  • Ex. Kangaroos having multiple babies a different developing stages

  
  
  3. Accelerated Development + Diapuse
  

  • Conditions harsh for long periods --> organism in diapause
  • Favorable conditions occur infrequently & last a short time
    
  •     Compressed lifecycle
  •     Harsh conditions --> diapause  (Spadefoot Toad)

• Evolutionary Senescence Model

  • "bad" mutations affecting young: strongly selected against
  • Bad mutation affecting old: persists (don't impinge on the fitness of the organism; doesn't affect the next generation)
  • Antagonistic Pleiotropy: Genes, which benefit early reproduction, have deleterious effects later in the lifespan. (Deterimental to older individuals but good for younger individuals)

• Mortality and Reproductive pattern

  Increase survivorship or decrease reproduction
  
  Decrease survivorship or increase production

• 2. Present vs. Future Reproduction

  Reproductive value: Vx = (mx) (lx)
  

  • decrease reprod (mx) >> increase Vx (& vice versa); if fairly low, then each individual is important
  • increase Survival (lx) >>  decrease Vx (& vice versa); each individual isn't as valuable, b/c they don't have to replace and individual as soon.

  
  Increase Reproduction --> Decrease Survival
  
  

  • Optimal strategy balances: Benefit of reproduction now vs cost of future reproduction.

• 3. Age at Sexual Maturity

  Natural Selection favors maturity at Early Age
  

  • More you can have over life
  • Low adult survival
  • ++ if semelparity species (But most species do not have offspring at a young age)

  
  
  When delayed reproduction is favored
  

  • High adult survival (invest yourself)
  • Reproductive success dependent on age, size, experience, etc. (male elk defending his harem)

• Theory of r and K (selection) species

  1. Classification
     
  2. For Each, distinct strategies evolve
  3. Bet-Hedging strategy

• For r & K, distinct strategies evolve

  r species
  

  • Natural selection favors E energy invested in reproduction over competitive ability (quick turnover rate)

  
  
  K species
  

  • Natural selection favors E energy invested in competitive ability over reproduction (can compete better; Maintenance over reproduction)

• Grimes' Plant Life History Strategy

  1. Environment variations ---> variable strategies
  
  2. Matched plant strategy with environment