NATURAL SELECTION, ADAPTATION AND MICROEVOLUTION

1. why do organisms live the way they do?
2. how has past evo shaped a trait or an orgnsm?
3. why can't nat sel. fashion perfect orgnsm?

   Nota:

   • correlated traits mutation allele lack of variation, can't change

1. LH traits can evolve rapidly
2. The factors driving evo can be tested
3. Translocation exp- guppy
   1. guppy popn in low and high predation area
      1. *selection can act on multiple co-adapted traits
      2. *the adaptiveness of traits & the drivers of evo can be tested
      3. * adapted traits are subjected to ongoing natural selection as environmental conditions change & continue to evolve
      4. Microevolution can lead to appreciable change that occurs rapidly on ecological timescales

1. if fitness is abt survival & reproduction? why can't they continuously produce high quality offspring and live forever?
   1. some orgnsm close to perfect, but only SOME of the traits (e.g.thrips egg mite, brown kiwi)
2. a) time & E an orgnsm can harvest is finite
3. b) biological processes take time
4. c) fundamental trade-offs in the set of traits.
5. d) increase fitness in one trait can reduce a fitness of another trait

1. 1) An evolutionary strategy
   1. a set of co-adapted traits which allow an organism to survive & adapt to their ecological niche
2. 2) Life history strategy (LHS)
   1. an orgnsm's investment in growth, maturation, reproduction, survival

Nota:

• LH traits are associated w fitness and are polygenic traits

1. Key qs in LH analysis
   1. Why live as long as they do?
   2. Why some reproduce once and others have many reproductive attempts during their lifespan?
   3. Why vary in the number of offspring they produce?
   4. Why vary in the time they take to become sexually mature?
2. 1) Trade-offs: Fecundity vs Lifespan
   1. e.g. rotifiers
      1. - produced lots of young, early in their life – had a shorter life
      2. - produced less young per day, lived longer and produced more young over their lifespan
   2. * High reproduction on one day decreases chances of survival to the next day
   3. * Reproduction is deleterious to future survival
3. Trade-offs: Current vs future reproduction
   1. e.g. Meadow grass
      1. the number of inflorescences per plant - produced in the 1st year or 2nd yr
         1. produce more in 1st yr, produce less in its 2nd yr
   2. e.g. collared flycatchers Ficedula albicollis
      1. some produce young in first yr, smaller clutch size, but their lifetime reproductive succesful is higher
      2. increase clutch size in the 1st year, the clutch size reduces with age
      3. young that was produced in bigger clutch size will have less clutch size itself
4. Predictable & unpredictable Env

   Nota:

   • rm = reproductive rate

1. * genetic drift causes random changes in allele/traits- popn can drift in diff directions and diverge.
2. * selection leads to adaptation to local conditions, & differences btwn popn can accumulate
3. * Limited gene flow + drift/selection can cause popns to diverge
4. * Low levels of gene flow help to maintain diversity & connection of popns & still allow adaptation to local conditions, high levels of gene flow may swap local selection
5. RING SP - two reproductively isolated forms are connected by a chain of intermediate populations
   1. Bridge between microevolution and speciation/ macroevolution
      1. Show the history of divergence of 2 sp & demonstrate how microevolutionary changes can accumulate into differences btwn sp.
      2. Show how geographical differentiation to the level of sp can occur in the face of ongoing gene flow
   2. e.g. Siberian Greenish warbler Phylloscopus trochiloides
      1. 2 populations that are not interbreeding - different morphology and song
      2. Interbreeding in intermediate popns around the ring