B-SC: Students will demonstrate an understanding of the history of life on Earth.

EVOLUTION of POPULATIONS

gene pool: combined genetic information of all members of a particular population

relative frequency: # of times an allele occurs in a gene pool compared with the # of times other alleles occur

defintions

In genetic terms, evolution is any change in the relative frequency of alleles in a population

2 main sources due to sexual reproduction (homologous chromosome independently assort in meiosis)

Sources of Genetic Variation

Sources of Genetic Variation1. MUTATIONS+/- changes

phenotype+/- changes

fitness

2. Gene Shuffling2. Gene ShufflingCause of most heritable differences

Humans have 8.4 million different combinations of genes

Single Gene TraitsWhen a single gene controls a phenotype

There are only 2 alleles: dominant & recessive

Natural selection on single-gene traits can lead to changes in allele frequencies which leads to evolution

http://www.google.com/imgres?q=natural+selection+in+a+nutshell&hl=en&safe=active&gbv=2&biw=1024&bih=504&tbm=isch&tbnid=aSC-iFef7mBvVM:&imgrefurl=http://evolution.berkeley.edu/evolibrary/article/bergstrom_02&docid=pyz52aB73uEhbM&imgurl=http://evolution.berkeley.edu/evolibrary/images/interviews/naturalselection3.gif&w=411&h=243&ei=wDNfT6PDGojegQeQpNHwBw&zoom=1

Polygenic TraitsControlled by 2 or more genes

Each gene has 2 or more alleles

3 different ways natural selection can affect phenotypes:

1. DIRECTIONAL SELECTION2. STABILIZING SELECTION3. DISRUPTIVE SELECTION

Natural Selection on Polygenic Traits

DIRECTIONAL SELECTIONWhen individuals at either end of the bell-shaped curve have an advantage the curve moves in direction of advantage

Stabilizing SelectionWhen individuals near the mean of the graph have advantage (higher fitness) the bell shape becomes taller

Disruptive SelectionWhen individuals at both extremes have advantage (or middle has decreasing fitness)the middle decreases

seen in small populationsmay see a particular allele producing more offspring than would happen by chance

over time a series of chance occurrences can make an uncommon allele common

Genetic Drift

Founder Effectwhen small sampling of large population colonizes new habitat & allele frequencies not representative of original population

http://www.google.com/imgres?q=founder+effect&hl=en&safe=active&biw=1024&bih=504&gbv=2&tbm=isch&tbnid=p0vP7eYJAiyNgM:&imgrefurl=http://www.web-books.com/eLibrary/ON/B0/B10/36MB10.html&docid=YAbBCXcg2tkN9M&imgurl=http://www.web-books.com/eLibrary/Books/B0/B10/MAIN/images/image036.jpg&w=570&h=428&ei=xotfT8bkGML-gge3xLSmCA&zoom=1

states that allele frequencies in a population will remain constant unless 1 or more factors cause those frequencies to change

when allele frequencies remain constant population is said to be in genetic equilibrium

Hardy-Weinberg Principle

1. Random Mating2. Large Population3. No Immigration or Emigration4. No Mutations5. No Natural Selection (all

genotypes have same chance of survival)

5 conditions necessary to maintain genetic equilibrium

Hardy-Weinberg Equation

Classification systems used to name organisms & to group them in a logical manner.

Linnaeus (Swedish botanist ) developed binomial nomenclature: 2 part name for every species (Genus species)Man: Homo sapiens

CLASSIFICATION

http://www.google.com/imgres?q=classification+of+living+things&hl=en&safe=active&gbv=2&biw=1024&bih=504&tbm=isch&tbnid=0qgBBgYp-W4t6M:&imgrefurl=http://blog.savcds.org/harrison/2011/02/08/classification-of-living-things/&docid=kfMABa0f6GjVgM&imgurl=http://blog.savcds.org/harrison/files/2011/02/Screen-shot-2011-02-08-at-7.40.19-AM1-300x255.png&w=300&h=255&ei=sJxfT9rGOcmwgwe7qP2YCA&zoom=1

TAXONOMYdiscipline of classifying organisms & assigning each organism a universally accepted name

the study of evolutionary relationships among organisms

Evolutionary ClassificationPHYLOGENY

Taxonomy Phyogeny

diagram that shows evolutionary relationships among a group of organisms

an evolutionary tree of life

Cladograms

page 453Hand in for grading

Quick Lab