Understanding the mechanisms of evolution: natural selection and genetic drift Dr. Timothy Greives Context: this unit fits within a larger unit focused on evolutionary mechanisms; students will have already learned

Evolution: Change over time We want to try to understand how this change occurs in nature and how variation affects this change. Lazuli Bunting Indigo Bunting ?

Introduction Brief introduction to concepts and terms Evolution: Change over time Biological Evolution: Change frequency of heritable traits over time. Genotype: An individuals set of genes determining a trait of interest (phenotype) Phenotype: The observed trait of interest. Phenotype is influenced by both the genotype and environment. Selection: A certain trait that influences reproductive success and survival (= total number of lifetime offspring)

Artificial selection Humans choose which trait to favor and breed individuals displaying those traits  increasing the total number of offspring in next generation. Wild tomato found in South America First cultivated by Native Americans Size influenced in part by changes in a single gene (fw2.2) - which encodes protein that represses cell division

Artificial selection Darwin studied the mechanism of evolution under domestication

Natural selection Individuals that are able to survive to produce more offspring will have higher fitness Instead of humans choosing the traits favored, nature will choose.

Evolution by (natural) selection

RE-Introduction Evolution: Biological Evolution: Genotype: Phenotype:

Experimental study system Simple model organisms Controlled environments Use the organism M&M to demonstrate Evolution

The elusive POISONOUS M&M Two color phenotypes of M&M’s Reproduces asexually by fission http://www.mms.com/#character

M&M fission http://www.mms.com/#character

M&M fission http://www.mms.com/#character

Reproduction by fission in real life

Please read through the activity instruction sheet silently. http://www.mms.com/#character

Questions? http://www.mms.com/#character

Please proceed through steps 1-4 http://www.mms.com/#character

Example of data sheets and graphs Group: __________________________ Date: _____________________ Generation Number of orange M & M's Number of blue M & M's Percentage of orange M & M's 10 50 1 4   2 7 3 5

Part II Form hypotheses for abundance of orange M&M’s after introduction of a chocovoire.

Please complete activity http://www.mms.com/#character

Evolution by Natural Selection in the Galapagos http://media.hhmi.org/biointeractive/films/OriginSpecies-Finches.html

Want to learn more about the finches?

Darwin’s finches “vampire finch” South America Darwin first noticed while on the Beagle (1831-1836) Grassquit colonized the islands from SA or CA 2.3 mya Different bills with different diets A few finches have managed to colonize these islands far from the South American continent. Their descendants have diversified to eat different items: different kinds of insects and seeds. This specialization can be seen in their beaks. Eventually birds that ate a specific kind of food started to mate more with each other than with other birds that ate other kinds of foods and they became separate species. Galapagos

Huntington’s Disease http://en.wikipedia.org/wiki/File:Neuron_with_mHtt_inclusion.jpg

Frequency of Huntington’s Disease Magazi et al. 2008. South African Medical Journal Greeff, JM. 2007. Annals of Human Genetics Hayden et al. 1980. South African Medical Journal http://www.freeworldmaps.net/outline/maps/world-map-outline.gif

http://www.freeworldmaps.net/outline/maps/world-map-outline.gif

http://www.freeworldmaps.net/outline/maps/world-map-outline.gif ‪https://commons.wikimedia.org/wiki/File:IJsselmeerTraditionalBoat.JPG

Frequency of Huntington’s Disease Magazi et al. 2008. South African Medical Journal Greeff, JM. 2007. Annals of Human Genetics Hayden et al. 1980. South African Medical Journal http://www.freeworldmaps.net/outline/maps/world-map-outline.gif

Huntington’s disease discussion Form hypotheses – why is prevelance so much higher in the Afrakaner Dutch descendents? Discuss hypotheses

http://www.mms.com/#character

Please read through the activity instruction sheet silently. http://www.mms.com/#character

Questions? http://www.mms.com/#character

Please proceed through steps 1-4 http://www.mms.com/#character

Please complete activity http://www.mms.com/#character

Following M&M exercise – revisit hypothesis regarding prevalence of Huntington’s disease in Afrikaner population Magazi et al. 2008. South African Medical Journal Greeff, JM. 2007. Annals of Human Genetics Hayden et al. 1980. South African Medical Journal http://www.freeworldmaps.net/outline/maps/world-map-outline.gif

Conservation case study http://www.hsd3.org/HighSchool/Teachers/MATTIXS/Mattix%20homepage/studentwork/Kyle%20Kohn%20web%20page/Cape%20buffalo.htm http://www.sharewallpapers.org/d/3444-1/Stampede---African-Cape-Buffalo-Herd-1.jpeg

Conservation case study Cape buffalo (Syncerus caffer caffer) Historically widespread and panmictic Currently confined to protected areas Isolation of populations How might this affect genetic diversity?

Heller et al. 2010. Molecular Ecology. 19:1324-1334

What is wrong with the statement ‘survival of the fittest’?

Darwin’s finches We can see how the different species of ground finches are specialized to eat different sized seeds. Could we see how selection may have driven this differentiation by looking a seed size preferences with in one species?

Diversity in traits Study skins of birds that have different diets. -Can they make hypotheses about diet based on their observation of beak size, other features?