Selection causes Microevolution

Selection causes Microevolution • Frequency of alleles (versions of a gene) changes in a population

Selection creates Adaptations Traits common to all members of a population Confer greater success

Selection can lead to Macroevolution Change on a grand scale macro Populations no longer interbreed Become more different over long periods of time micro

Selection can lead to Macroevolution = different species

From Microevolution to Macroevolution Geographic Isolation Ensatina salamanders Inhabit the CA coast, and Sierra foothills, but not the hot , dry Central Valley

Geographic isolation causes Reproductive isolation Do not interbreed Functionally separate species Interbreed

Organisms that interbreed, producing viable, fertile, offspring Species? • A mule is neither horse nor donkey The evolution of a species is called speciation

Geographic isolation causes Reproductive isolation

Geographic isolation causes Reproductive isolation Grand Canyon

Other factors also cause Reproductive isolation Sexual selection

Other factors also cause Reproductive isolation Behavior Timing Lay eggs later, in ripe fruit Lay eggs in green (early) fruit Mature at different times, reproductively isolated

Once isolated, the populations become less and less alike Yes, via selection but also via unique genetic mutations Random mutation creates green phenotype

Once isolated, the populations become less and less alike Yes, via selection but also via genetic drift random changes, not directed Random chance event causing changes in allele frequencies

Genetic drift Most apparent in small populations Net loss of variation/diversity 30,000 today Of 24 genes studied no allelic variation Ex: bottleneck event 20 Northern Elephant Seals Hunted population

Ex: founders effect Genetic drift Small founding population with less genetic variation than the original During a Caribbean hurricane, Green iguanas are rafted to Anguilla from Guadeloupe

Gene Flow causes change (aka evolution) too pollination spreads sperm Movement of genes - via individuals or gametes - between populations

Gene Flow causes change (aka evolution) too More or less alike in time? Movement of genes, via individuals or gametes between populations immigration emigration

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Bottleneck, Gene Flow or Founder Effect? • Which type of event explains the high incidence of polydactylism found in the Amish population? Founder Effect

Bottleneck, Gene Flow or Founder Effect? • Flower population: ww = white flower; WW and Ww = purple flower; a mud slide wipes out most of the white flowered plants. What type of event occurred? Bottleneck

Bottleneck, Gene Flow or Founder Effect? • Genetic modifications from transgenic plants passed to neighboring populations of wild relatives. What type of event occurred? Gene Flow

Bottleneck, Gene Flow or Founder Effect? • Millions of greater prairie chickens once lived on the prairies of Illinois. As these prairies were converted to farmland and other uses during the 19th and 20th century, the number of greater prairie chickens plummeted to less than 50 individuals. The few survivors have low levels of genetic variation. What type of event occurred? Bottleneck

Bottleneck, Gene Flow, or Founder Effect? • This event resulted in the world wide spread of several insecitcide-resistance alleles in the mosquito Cluexpipiens, a vector for West Nile virus and Malaria. What type of event occurred? Gene Flow

Bottleneck, Gene Flow or Founder Effect? • A few weeks after two major hurricanes swept through the Caribbean islands, fishermen on the island of The allele frequencies for the founding population on Anguilla differed from those on Guadeloupe. What type of event occurred? Founder Effect

Selection causes Microevolution