Evolution of Populations 2007-2008 Doonesbury - Sunday February 8, 2004

Presence of lactate dehydrogenase Populations evolve Natural selection acts on individuals differential survival “survival of the fittest” differential reproductive success who bears more offspring Populations evolve genetic makeup of population changes over time favorable traits (greater fitness) become more common Presence of lactate dehydrogenase The Mummichog (Fundulus heteroclitus heteroclitus) is a small killifish found in the eastern United States. It is capable of tolerating highly variable salinity and temperatures, and is found in estuaries and saltmarshes as well as less salty waters. A year-round resident of tidal creeks and wetlands, this brownish-green saltwater minnow may reach a maximum length of 5 inches. Its Indian name means "they go in great numbers." It is also known as the common killifish. A hardy fish, the mummichog is an important food source for larger fish and is often used as bait. The mummichog also has been used as a natural method of mosquito control in marsh ponds and ditches. It has been reported that one mummichog can eat as many as 2,000 mosquito larvae ("wrigglers") a day. The mummichog also feeds on other insects, small fish, crustaceans, and plant material. Because of the extreme hardiness of the species, it is sometimes the only species found in severely polluted and oxygen-deprived streams, such as the Hackensack River and the Arthur Kill in New Jersey during the height of the water pollution problem in the United States. In 1973 the Mummichog became the first fish in space when carried on Skylab 3 as part of the biological experiments package later space missions by the U.S., such as Bion 3, have also carried Mummichog. Mummichog

Changes in populations Bent Grass on toxic mine site Pocket Mice in desert lava flows Pesticide molecule Insect cell membrane Target site Resistant target site Bent Grass growing on mine tailings; only individuals tolerant of toxic heavy metals will grow from the seeds blown in from nearby field Target site Decreased number of target sites Insecticide resistance

Individuals DON’T evolve… Individuals survive or don’t survive… Individuals DON’T evolve… Individuals are selected Populations evolve Individuals reproduce or don’t… 2007-2008

Fitness Survival & Reproductive success Body size & egg laying in water striders Fitness Survival & Reproductive success individuals with one phenotype leave more surviving offspring

Variation & natural selection Variation is the raw material for natural selection there have to be differences within population some individuals must be more fit than others

Where does Variation come from? Mean beak depth of parents (mm) Medium ground finch 8 9 10 11 1977 1980 1982 1984 Dry year Wet year Beak depth Beak depth of offspring (mm) Mutation random changes to DNA errors in mitosis & meiosis environmental damage Sex mixing of alleles recombination of alleles new arrangements in every offspring new combinations = new phenotypes spreads variation offspring inherit traits from parent

5 Agents of evolutionary change Mutation Gene Flow Non-random mating Genetic Drift Selection

Not every mutation has a visible effect. 1. Mutation & Variation Mutation creates variation new mutations are constantly appearing Mutation changes DNA sequence changes amino acid sequence? changes protein? changes structure? changes function? changes in protein may change phenotype & therefore change fitness Every individual has hundreds of mutations 1 in 100,000 bases copied 3 billion bases in human genome But most happen in introns, spacers, junk of various kind Not every mutation has a visible effect. Some effects on subtle. May just affect rate of expression of a gene.

2. Gene Flow Movement of individuals & alleles in & out of populations seed & pollen distribution by wind & insect migration of animals sub-populations may have different allele frequencies causes genetic mixing across regions reduce differences between populations

Are we moving towards a blended world? Human evolution today Gene flow in human populations is increasing today transferring alleles between populations Are we moving towards a blended world?

3. Non-random mating Sexual selection

4. Genetic drift Effect of chance events founder effect bottleneck small group splinters off & starts a new colony bottleneck some factor (disaster) reduces population to small number & then population recovers & expands again 1 family has a lot of children & grandchildren therefore has a greater impact on the genes in the population than other families Genghis Khan tracked through Y chromosome. Warbler finch Tree finches Ground finches

Founder effect When a new population is started by only a few individuals some rare alleles may be at high frequency; others may be missing skew the gene pool of new population human populations that started from small group of colonists example: colonization of New World Small founder group, less genetic diversity than Africans All white people around the world are descended from a small group of ancestors 100,000 years ago (Chinese are white people!)

Distribution of blood types Distribution of the O type blood allele in native populations of the world reflects original settlement South & Central American Indians were nearly 100% type O for the ABO blood system. Since nothing in nature seems to strongly select for or against this trait, it is likely that most of these people are descendants of a small band of closely related "founders" who also shared this blood type

Distribution of blood types Distribution of the B type blood allele in native populations of the world reflects original migration The global frequency patterns of the type B blood allele: Note that it is highest in central Asia and lowest in the Americas and Australia. However, there are relatively high frequency pockets in Africa as well. Overall in the world, B is the rarest ABO blood allele.

Out of Africa Likely migration paths of humans out of Africa 10-20,000ya 10-20,000ya Migration Paths According to the "Out of Africa" theory, modern humans appeared as a single African species nearly 100,000 years ago, then spread throughout the world (K.Wong, Is Out of Africa Going Out the Door?, Scientific American 281(2), August 1999). 50,000ya Many patterns of human traits reflect this migration

Bottleneck effect When large population is drastically reduced by a disaster famine, natural disaster, loss of habitat… loss of variation by chance event alleles lost from gene pool not due to fitness narrows the gene pool

Cheetahs All cheetahs share a small number of alleles 2 bottlenecks less than 1% diversity as if all cheetahs are identical twins 2 bottlenecks 10,000 years ago Ice Age last 100 years poaching & loss of habitat

Peregrine Falcon Conservation issues Bottlenecking is an important concept in conservation biology of endangered species loss of alleles from gene pool reduces variation reduces adaptability Breeding programs must consciously outcross Golden Lion Tamarin

5. Natural selection Differential survival & reproduction due to changing environmental conditions climate change food source availability predators, parasites, diseases toxins combinations of alleles that provide “fitness” increase in the population adaptive evolutionary change

5 Agents of evolutionary change Mutation Gene Flow Non-random mating Genetic Drift Selection

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