Evolution Basics (PDF)

http://evolution.berkeley.edu Bowman Ch. 6 Review: Evolution, Natural Selection & Adaptation in the context of Ecology BIOL2050 Ecology Instructor: Dr. Birgit Schwarz [email protected] ...

http://evolution.berkeley.edu Bowman Ch. 6 Review: Evolution, Natural Selection & Adaptation in the context of Ecology BIOL2050 Ecology Instructor: Dr. Birgit Schwarz [email protected]  Evolution Microevolution Changes in allele frequencies in a population over time (generations) University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu)  Take note Individuals don’t evolve, populations do! Observable Humans can cause changes don’t take evolutionary millions of years change  Evolution Microevolution Macroevolution Changes in allele frequencies Descent with modification: how in a population over time species change over time & new (generations) species arise University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu)  Evolution Microevolution Macroevolution Changes in allele frequencies Descent with modification: how in a population over time species change over time & new (generations) species arise University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu)  Take note Individuals don’t evolve, populations do! Observable Humans can cause changes don’t take evolutionary millions of years change How can the genetic make-up of a population change? Mutation Gene flow Genetic Drift Natural or sexual selection →mechanisms (or drivers) of evolution Images: University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu)  Evolution by Natural Selection Images: University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu) Evolution Adaptation Species change over time and become adapted to their environment  Natural selection acts only on HERITABLE (i.e., genetic) variation Heritability of a trait = proportion of variation in the trait that is due to genetic variation  Seasonal change in fur colour of arctic animals is not an evolutionary change Summer: brown fur Winter: white fur → the genetic makeup of individual animals cannot change → Traits have to be heritable & there has to be genetic variation for evolution to occur Natural selection results in ADAPTATIONS = traits that improve survival and reproduction in a given environment Fitness depends on the environment! Natural selection results in ADAPTATIONS = traits that improve survival and reproduction in a given environment Fitness depends on the environment! “Fitness” = ability to reproduce relative to other individuals in the population Phenotype = traits (outward appearance) of an organism shaped by genes, environment & interaction betw. genes & environm. Genotype = genetic makeup of an organism → Not all variation within a species is genetically based  Take note Mutations happen randomly Natural selection can only act (with respect to fitness!) on existing, genetic variation Don’t happen because they are needed Does not create new variation! Environment determines if a particular Can only work with existing variation mutation conveys an advantage or not → no perfect organisms Adaptation of organisms to their environment is never perfect Other reasons: 1. Trade-offs Male Guppies Male from population with high predation levels Male from population with low predation levels Adaptation of organisms to their environment is never perfect Other reasons: 1. Trade-offs 2. Environmental change or variability Felicity Burke/The Conversation, CC BY Adaptation of organisms to their environment is never perfect Other reasons: 1. Trade-offs 2. Environmental change or variability 3. Chance Adaptation of organisms to their environment is never perfect Other reasons: 1. Trade-offs 2. Environmental change or variability 3. Chance 4. Genetic factors http://pleiotropy.fieldofscience.com/ 2012/09/epistasis-in-evolution.html