Selection causes Microevolution
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Transcript of Selection causes Microevolution
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Selection causes Microevolution• Frequency of alleles (versions of a gene) changes in a population
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Selection creates Adaptations
Traits common to all members of a populationConfer greater success
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Selection can lead to Macroevolution
Populations no longer interbreed Become more different over long periods of time
micro
macro
Change on a grand scale
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Selection can lead to Macroevolution
= different species
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Ensatina salamanders
Inhabit the CA coast, and Sierra foothills, but not the hot , dry Central Valley
From Microevolution to Macroevolution Geographic Isolation
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Geographic isolation causes Reproductive isolation
Interbreed
Do not interbreed
Functionally separate species
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Species? Organisms that interbreed, producing viable, fertile, offspring
A mule is neither horse nor donkey
The evolution of a species is called speciation
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Geographic isolation causes Reproductive isolation
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Geographic isolation causes Reproductive isolation
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Geographic isolation causes Reproductive isolation
Grand Canyon
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Other factors also cause Reproductive isolation
Sexual selection
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Other factors also cause Reproductive isolation
Behavior
TimingLay eggs in green (early) fruit
Lay eggs later, in ripe fruit
Mature at different times, reproductively isolated
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Once isolated, the populations become less and less alikeYes, via selection but also
via unique genetic mutationsRandom mutation creates green phenotype
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Once isolated, the populations become less and less alike
Random chance event causing changes in allele frequencies
Yes, via selection but alsovia genetic drift random changes, not directed
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Genetic drift
Most apparent in small populationsNet loss of variation/diversity
Ex: bottleneck event
20 Northern Elephant Seals
30,000 todayOf 24 genes studied no allelic variation
Hunted population
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Genetic drift Ex: founders effect
Small founding population with less genetic variation than the original
During a Caribbean hurricane, Green iguanas are rafted to Anguilla from Guadeloupe
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Gene Flow causes change (aka evolution) too
Movement of genes - via individuals or gametes - between populations
pollination spreads sperm
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Gene Flow causes change (aka evolution) too
Movement of genes, via individuals or gametes between populations
immigrationemigration
More or less alike in time?
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• Reformat following slides
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• Which type of event explains the high incidence of polydactylism found in the Amish population?
Bottleneck, Gene Flow or Founder Effect?
Founder Effect
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• 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, Gene Flow or Founder Effect?
Bottleneck
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• Genetic modifications from transgenic plants passed to neighboring populations of wild relatives. What type of event occurred?
Bottleneck, Gene Flow or Founder Effect?
Gene Flow
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• 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, Gene Flow or Founder Effect?
Bottleneck
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• This event resulted in the world wide spread of several insecitcide-resistance alleles in the mosquito Cluex pipiens, a vector for West Nile virus and Malaria. What type of event occurred?
Bottleneck, Gene Flow, or Founder Effect?
Gene Flow
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• 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?
Bottleneck, Gene Flow or Founder Effect?
Founder Effect