Evolution of populations
1 / 27

EVOLUTION of POPULATIONS - PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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

Sources of Genetic Variation

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

Sources of Genetic Variation


    +/- changes phenotype

    +/- changes fitness

2. Gene Shuffling

2. Gene Shuffling

  • Cause of most heritable differences

  • Humans have 8.4 million different combinations of genes

Single Gene Traits

  • 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

Polygenic Traits

  • Controlled by 2 or more genes

  • Each gene has 2 or more alleles

Natural Selection on Polygenic Traits

  • 3 different ways natural selection can affect phenotypes:





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

Stabilizing Selection

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

Disruptive Selection

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

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

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

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

  • Random Mating

  • Large Population

  • No Immigration or Emigration

  • No Mutations

  • No Natural Selection (all genotypes have same chance of survival)

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

Evolutionary Classification



  • discipline of classifying organisms & assigning each organism a universally accepted name

  • the study of evolutionary relationships among organisms




  • diagram that shows evolutionary relationships among a group of organisms

  • an evolutionary tree of life

Quick Lab

page 453

Hand in for grading

  • Login