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

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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


Evolution of populations

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


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


Evolution of populations

  • 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)


Hardy weinberg equation

Hardy-Weinberg Equation


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


Evolution of populations

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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