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

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

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)

1. MUTATIONS +/- changes phenotype +/- changes fitness

2. Gene Shuffling Cause of most heritable differences Humans have 8.4 million different combinations of genes

When 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

Controlled by 2 or more genes Each gene has 2 or more alleles

3 different ways natural selection can affect phenotypes: 1. DIRECTIONAL SELECTION 2. STABILIZING SELECTION 3. DISRUPTIVE SELECTION

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

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

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

seen in small populations may 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

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

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

1. Random Mating 2. Large Population 3. No Immigration or Emigration 4. No Mutations 5. No Natural Selection (all genotypes have same chance of survival)

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

TAXONOMY discipline of classifying organisms & assigning each organism a universally accepted name the study of evolutionary relationships among organisms PHYLOGENY

TaxonomyPhyogeny

diagram that shows evolutionary relationships among a group of organisms an evolutionary tree of life

page 453 Hand in for grading