evolution of populations
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EVOLUTION of POPULATIONS. B-SC: Students will demonstrate an understanding of the history of life on Earth. . defintions. gene pool : combined genetic information of all members of a particular population

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evolution of populations

EVOLUTION of POPULATIONS

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

defintions
defintions
  • 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
sources of genetic variation
Sources of Genetic Variation
  • 2 main sources due to sexual reproduction (homologous chromosome independently assort in meiosis)
sources of genetic variation1
Sources of Genetic Variation
  • MUTATIONS

+/- changes phenotype

+/- changes fitness

2 gene shuffling
2. Gene Shuffling

2. Gene Shuffling

  • Cause of most heritable differences
  • Humans have 8.4 million different combinations of genes
single gene traits
Single Gene Traits
  • When a single gene controls a phenotype
  • There are only 2 alleles: dominant & recessive
slide8

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

polygenic traits
Polygenic Traits
  • Controlled by 2 or more genes
  • Each gene has 2 or more alleles
natural selection on polygenic traits
Natural Selection on Polygenic Traits
  • 3 different ways natural selection can affect phenotypes:
  • DIRECTIONAL SELECTION
  • STABILIZING SELECTION
  • DISRUPTIVE SELECTION
directional selection
DIRECTIONAL SELECTION
  • When individuals at either end of the bell-shaped curve have an advantage the curve moves in direction of advantage
stabilizing selection
Stabilizing Selection
  • When individuals near the mean of the graph have advantage (higher fitness) the bell shape becomes taller
disruptive selection
Disruptive Selection
  • When individuals at both extremes have advantage (or middle has decreasing fitness)the middle decreases
genetic drift
Genetic Drift
  • 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
founder effect
Founder Effect
  • when small sampling of large population colonizes new habitat & allele frequencies not representative of original population
hardy weinberg principle
Hardy-Weinberg Principle
  • 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
5 conditions necessary to maintain genetic equilibrium
5 conditions necessary to maintain genetic equilibrium
  • Random Mating
  • Large Population
  • No Immigration or Emigration
  • No Mutations
  • No Natural Selection (all genotypes have same chance of survival)
classification
CLASSIFICATION
  • 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
evolutionary classification
Evolutionary Classification

TAXONOMY

PHYLOGENY

  • discipline of classifying organisms & assigning each organism a universally accepted name
  • the study of evolutionary relationships among organisms
slide24
Taxonomy

Phyogeny

cladograms
Cladograms
  • diagram that shows evolutionary relationships among a group of organisms
  • an evolutionary tree of life
quick lab
Quick Lab

page 453

Hand in for grading

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