Microevolution

Bell work Explain how the sequence of amino acids in a protein and homologous structures provide evidence of evolution.

Objectives Define population. Contrast macroevolution and microevolution. Explain Hardy Weinberg Equilibrium. List Evolutionary Agents that cause allele frequencies to deviate from Hardy Weinberg Equilibrium.

Key Terminology Population Microevolution Macroevolution Hardy-Weinberg Equilibrium Gene Pool Gene Flow Species Genetic Drift Bottleneck Effect Founder Effect Sexual Selection Intersexual selection Intrasexual selection Antibiotic Resistance

Microevolution Evolution on smallest scale Definition: Change in the frequency of alleles within a population from generation to generation Review: What is an allele?

How do the Peppered Moths demonstrate Microevolution?

Comparison to Macroevolution Definition: Macroevolution examines changes over Earth’s history from the time Earth was created until now Microevolution –looks at changes of an organism from generation to generation

Key terms used in microevolution Population Group of individuals of the same species living at the same place and the same time. Considered the smallest unit to evolve. Biological species Group of populations whose individuals have the potential to interbreed and produce fertile offspring

Key terms used in microevolution Gene pool All the alleles in all the individuals that make up a population

How evolution is measured in a population Measure how the alleles change in a population across generations Two alleles found in a population Dominant allele=p Recessive allele=q p and q represent the frequency of allele Frequency = total number of dominant (p) or recessive alleles (q) divided by the total number of individuals in the population.

Sample problem In a population of 1000 guinea pigs, 600 have the dominant allele for rough coat and 400 have the recessive allele for smooth coat. Calculate p and q.

Answer to Sample Problem p=.6, q=.4

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share If evolution did not occur what would happen to the frequency of alleles over ten generations? 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Hardy Weinberg Equilibrium States that the frequency of dominant and recessive alleles stays constant across generations.

Five conditions must be met to achieve Hardy Weinberg Equilibrium Population is very large Population is isolated – no individuals moving in or out Mutations do not alter the gene pool Mating is random All individuals are equal in reproductive success; natural selection does not occur

Hardy Weinberg is not achieved in nature. Why do we care? Provides a baseline so we can recognize when a population’s gene pool is changing Evidence that microevolution is occurring

3 Minute Paper You have 3 minutes to explain Microevolution and how Hardy-Weinberg Equilibrium is used to study it. Be ready to share.

Evolutionary Agents that alter Allele Frequency

Genetic Drift Occurs when population is small In a small population, individuals that carry a particular allele have more offspring than other individuals. Over time that allele becomes more common in the gene pool Two types of genetic drift Bottleneck effect Founder effect

Bottleneck effect Bottleneck effect – catastrophic event (earthquake, flood, fire) reduces population size Reduced population size has different allele frequency than original population Example Bubonic Plague killed 1/3 of European population

Founder Effect Colonization of new location by a small number of individuals with different allele frequency than original population. Examples Iguanas from South American mainland populating Galapagos Islands Dutch Afrikaners of South Africa have high rate of Huntington’s Disease

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share Why does reduction in population size increase the chances of genetic drift? 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Gene Flow Gain or loss of alleles from a population by movement of individuals or gametes Result of migration Reduces genetic differences between populations compared to isolated populations

Example of how Gene Flow changes Allele Frequency

Mutation Random change in the DNA Vital to evolution because the only mechanism that creates new alleles Because mutation rates low, has little effect on Hardy Weinberg allele proportion

Non-random mating-sexual selection Selection of mates other than by chance Mating generally not random attracted to particular phenotypic traits Two types of sexual selection Intrasexual selection: competition within same sex Intersexual selection-attraction between opposite sex

Intrasexual Selection males compete between themselves for female’s attention Example: battle between two male elk for female attention

Intersexual Selection Female’s attraction to male’s features. Example: Female Peacock attracted to male’s peacock tail

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share Explain why sexual selection is a form of natural selection. 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Natural Selection For natural selection to occur the following conditions must be met There must be genetic variation within population Genetic Variation results in unequal reproductive success Example antibiotic resistance in bacteria

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share Explain why the following statement is incorrect: “Antibiotics have created resistant bacteria” 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Letter or Note to a Friend Write a note to a absent classmate explaining how evolutionary agents cause allele frequencies to deviate from Hardy Weinberg Equilibrium 27. Letter or Note to a Friend teacher instructs students to write a note to a friend or absent classmate explaining the learning teacher uses think-pair-share or collects to review PROPERTY OF PIMA COUNTY JTED, 2010 32