Speciation
Biology 2
Thursday, January 24, 2013
Evolution
• Change in the genetic composition
of a group of organisms over time.
• Descent with modification
Thursday, January 24, 2013
Microevolution
•
•
Changes within species
Short Time Period
• e.g. Tuskless Elephants
• e.g. Peppered Moths/Coloration
• e.g. Bacteria/Antibiotic Resistance
Thursday, January 24, 2013
Macroevolution
• Changes over longer time periods
• Speciation - evolution of 2 or more
species from a single species
Species B
Species C
Species A
Thursday, January 24, 2013
Adaptive Radiation
• One species evolves into many.
Multiple Descendent Species
Extinction
Time
Ancestral Species
Thursday, January 24, 2013
Activity 4
Speciation of
Caminalcules
Thursday, January 24, 2013
Speciation of Caminalcules
Gradualism
Punctuated Equilibrium
Time
Morphology
Thursday, January 24, 2013
Morphology
Species
• Biological Concept
• Group of similarly constructed organisms
that interbreed and produce fertile
offspring
Thursday, January 24, 2013
Reproductive Isolating
Mechanisms
• Prezygotic - prevents fertilization
• Postzygotic - prevents development
Good Summary
Text Figure 17.4
Thursday, January 24, 2013
Prezygotic Isolating Mechanisms
1.
Habitat Isolation - live different habitats
Tree Canopy
Ground
Thursday, January 24, 2013
Prezygotic Isolating Mechanisms
2.
Temporal Isolation - breed different times
Squirrel Corn
Thursday, January 24, 2013
Dutchman’s Britches
Prezygotic Isolating Mechanisms
3.
Behavioral Isolation - different courtships
Blue-Footed Bobbies
Dancing
Bird
Songs
Fireflies
Flashing
Thursday, January 24, 2013
Prezygotic Isolating Mechanisms
4.
Mechanical isolation - incompatible
reproductive parts
birch and passion flower
pollen on passion flower
Thursday, January 24, 2013
Postzygotic Isolating Mechanisms
• Zygote Mortality
• Hybrid Sterility
Horse
• Hybrid Fitness
Mule
Thursday, January 24, 2013
Donkey
Species
• Evolutionary Concept
• Members of same
species have similar
structure
• Can be applied to sexual
and asexual reproduction.
• Can be applied to fossils
Thursday, January 24, 2013
Speciation
• Evolution of 2 or more species from a
single species
Species B
Species C
Species A
Thursday, January 24, 2013
Types of Speciation
• Allopatric Speciation - geographical
separation
• Sympatric Speciation - same
geographical area
Thursday, January 24, 2013
Allopatric
Speciation
Textbook Figure 17.8
California
Salamanders
separated by large
central valley
Thursday, January 24, 2013
Allopatric Speciation
Darwin’s Finches - Different Islands
http://www.pbs.org/wgbh/evolution/library/01/6/
image_pop/l_016_02.html
http://people.rit.edu/rhrsbi/GalapagosPages/SlideShow/
SlidePages/Darwin's%20Finches.html
Thursday, January 24, 2013
Types of Speciation
• Allopatric Speciation - geographical
separation
• Sympatric Speciation - same
geographical area
• Hybridization
• Polyploidy
Thursday, January 24, 2013
Hybridization
• Crossing 2 different strains or related species.
• Result in new species
Wheat
Type
1
Wheat
Type
2
hybrid
wheat
Thursday, January 24, 2013
Polyploidy
• Having more than 2 pairs of chromosomes
2N
Diploid
Thursday, January 24, 2013
3N
4N
Polyploids
Normal Meiosis
Fertilization
Egg/Sperm
+
Egg
Sperm
Thursday, January 24, 2013
Zygote
Polyploidy
• Chromosomes fail to separate in meiosis
Egg
Sperm
+
Thursday, January 24, 2013
Zygote
Sympatric Speciation
Polyploidy
• Chromosome doubling due to no meiosis after
replication
Thursday, January 24, 2013
Wheat Evolution
7
14
Triticum
gamete
momococcum
2N = 14
Hybrid (Infertile)
gamete
Triticum turgidum
2N = 28
21
chromosome
doubling
Modern Wheat
Triticum fauschi
2N = 42
Thursday, January 24, 2013
42